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2007 isuzu ascender
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Discussion Starter #1
Hi guys,

For a couple of weeks now, I've had a problem with my horn that I have yet to hunt down. My horn basically works when it wants to. The fuse is not blown, there is nothing that happens (that I've noticed) to cause this. I can tell; however, when it is working again. There is a "click" heard seemingly coming from the IPC area. I've tested the horn module itself and it works fine, the contact points at the wheel itself seem to be working as I performed a voltage drop test. I have the stabilitrack light issue but I'm not sure if it's related. I get the following codes from the ABS when I use the code reader. U1000, U1016 and DTC0455.

Please help, this is driving me crazy and is very dangerous! I still have warranty left, but I was hoping to at least fix the horn myself. :eek::tiphat
 

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I am having a somewhat similar issue. My horn works very infrequently when I try to push the horn on the steering wheel. It works fine every time when I lock my TB with my keyless remote. I'm assuming mine has something to do with a wire, I just have yet to make it into the dealer for it to get fixed.

What is the Stabilitrak issue? I missed that post. I had an issue with that once when the "Service Stabilitrak" came over the DIC, and my light stayed on. But, when I parked it, and re-started it, that went away and hasn't came back on since.
 

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2007 chevy trailblazer_ls
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Here's a TSB for the horn. Sorry, I can't post the pictures that go with the bulletin.
Mark

#07-08-54-001C: EI07279 - Horn Inoperative from Steering Wheel Horn Pad (Ground Path Repair Procedure) - (Oct 17, 2008)


Subject: EI07279 -- Horn Inoperative from Steering Wheel Horn Pad (Ground Path Repair Procedure)


Models: 2006-2007 Buick Rainier

2006 Chevrolet TrailBlazer EXT

2006-2009 Chevrolet TrailBlazer

2006 GMC Envoy XL, Envoy XUV

2006-2009 GMC Envoy, Envoy Denali




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This bulletin is being revised to provide field fix information. Please discard Corporate Bulletin Number 07-08-54-001B (Section 08 -- Body and Accessories).


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Condition
Important: If the horn does NOT work from the key fob horn button, disregard this bulletin and proceed with diagnosis/repair according to SI.

Some customers may comment that the horn is inoperative from the horn pad on the steering wheel.

Cause
The general cause of this condition is high resistance in the ground path through the steering column that energizes the horn relay. The key fob panic button uses a different ground path and is not affected. A number of locations in the circuit have been identified as sources of the high resistance. It is often difficult to pinpoint the specific location of the high resistance because the condition is usually intermittent. Attempting to discover the location can be frustrating because as circuit components are moved, the condition will often disappear. A few locations have been identified as frequent contributors to the problem.

Correction
Complete the following steps to diagnose and repair this condition:

Does the horn work by depressing the button(s) on the key fob?
• Yes -- proceed with step 2.

• No -- do not proceed with this bulletin. Diagnose and repair using information found in SI.

To aid in the diagnosis and to avoid disturbing others, disconnect the wiring harness from the horn assembly and insert appropriate connectors to monitor the voltage with a multi-meter or a test light. If the horn pad is currently working, rotate the steering wheel lock to lock while depressing the horn pad to determine if there are any spots in the rotation where the horn pad quits working.
Caution: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling. Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs.








Remove the Inflatable Restraint Steering Wheel Module using the procedure found in Service Information. Remove the horn contacts from the steering wheel. Clean the brass contact on the end of the red wires with an abrasive pad. If possible, remove any contamination present on the mating contact on the cancel cam (inside the black tube). Also clean the four copper rivets embedded in the steering wheel frame. Apply GM Dielectric Lubricant to all the contacts to protect against reoccurrence of the corrosion. Refer to the graphic.
Reinstall the horn contacts and the Inflatable Restraint Steering Wheel Module and test for proper operation of the horn pad. Test for proper operation of the horn pad through the entire steering wheel rotation. Does the horn pad work properly?
• Yes -- repair is complete.

• No -- proceed with step 5.

Is the inoperative condition only present at certain steering wheel positions?
• Yes -- proceed with step 6.

• No -- proceed with step 9.

Remove the steering column trim covers. Position the steering wheel on a dead spot. Ground a test light to the steering column frame close to the steering wheel. Probe the surface of the turn signal cancel cam with the test light. Does grounding the cam activate the horn?
• Yes -- this may mean that the contact of the cancel cam that mates to the horn contact wiring harness contact, may not be clean enough or that the cancel cam may need to be replaced. Repair as necessary. Procedure complete.

• No -- proceed with step 7.

Turn Signal Cancel Cam:




Disconnect the wiring harness that goes to the top of the multi-function switch (connector X1). Using the grounded test light, touch the harness connection for pin G. Does grounding the pin activate the horn?
• Yes -- proceed with step 8.

• No -- try grounding the test light on a known good ground. If this activates the horn, proceed to step 9. If not, investigate a possible condition with the wiring harness or BCM with appropriate SI documents.





The condition lies either in the multi-function switch or the interface between the multi-function switch and the cancel cam. In some cases, removing the multi-function switch and clearing the horn contact that mates with the cancel cam (refer to the graphic) of debris and reinstalling the switch will eliminate the condition. In other cases, the cancel cam may be losing contact with the multi-function switch contact. If distortion in the cancel cam is present, it may be necessary to replace the cancel cam. Repair as necessary. Procedure complete.
Remove the left side IP insulator (refer to Instrument Panel Insulator Panel Replacement found in SI) so it can be moved aside enough to see the steering column.
Depress the horn contacts in the steering wheel. Does the horn work?
• Yes -- Check if the operation of the horn is sensitive to pressure applied to the steering wheel as if a driver were doing a panic stop. In some cases, pressure applied to the steering wheel in different directions will expose a bad ground path in the steering column. Proceed to step 11.

• No -- proceed with step 11.

Inspect the steering column through the insulator panel location.
Note: The shaft from the steering wheel comes through a metal bracket. That bracket is surrounded by plastic, which is inside of another metal bracket. Look for a small metal clip (refer to the "horn clip" graphic) that connects the inner bracket (inside the plastic) and the outer bracket. This clip provides an auxiliary ground path which is needed in some cases, if the primary path has a bad connection.

Horn Clip:




To verify this, connect a test light between the red wire on the horn contacts in the steering wheel and the steering column sections (1) and (2) in the illustration. Does the horn work when grounded to (1) and not (2)?
• Yes -- add or replace the horn clip.

• No -- refer to the Horn Inoperative section in SI to diagnose which component in the circuit is causing the horn inoperative condition.

Parts Information
Part Number
Description

19208609
Clip -- Horn Wire Ground
 

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#08-05-25-005: Intermittent StabiliTrak Indicator Light Blinking, StabiliTrak Active Message Displayed, DTC C0196 Set (Reprogram Electronic Brake Control Module (EBCM)) - (Oct 1, 2008)


Subject: Intermittent StabiliTrak® Indicator Light Blinking, StabiliTrak® Active Message Displayed, DTC C0196 Set (Reprogram Electronic Brake Control Module (EBCM))


Models: 2006-2007 Buick Rainier

2006-2009 Chevrolet TrailBlazer Models

2006-2009 GMC Envoy Models

2006-2009 Saab 9-7X

2006-2009 Isuzu Ascender Models




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This bulletin provides information on two different conditions.

Condition #1
Some customers may comment on a Service StabiliTrak® indicator light along with a Service StabiliTrak® message displayed in the DIC. Upon investigation, the technician may find DTC C0196 set in history.

Condition #2
Some customers may comment on a blinking StabiliTrak® indicator light along with a StabiliTrak Active message displayed in the DIC during normal driving conditions. No DTCs will be found with this concern.

Cause
This condition may be caused by a software anomaly within the electronic brake control module (EBCM) that allowed the yaw offset to be falsely learned.

Correction
Do This
Don't Do This

Reprogram the EBCM.
Do not replace the yaw sensor or EBCM for this condition.


Important: From the controller list, select "VSES Vehicle Stability Enhancement System Control Module."

If routine diagnosis using SI does not reveal any obvious cause, reprogram the EBCM using SPS with the latest software available on TIS2WEB. Refer to the Service Programming System (SPS) procedures in SI. As always, make sure your Tech 2® is updated with the latest software version.
 

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Diagnosis for code U1000

DTC U1000
Circuit Description
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within 5 seconds of beginning serial data communication, DTC U1000 is set. When more than one critical parameter does not have an identification number associated with it, the DTC will only be reported once.

The class 2 serial data line on this vehicle is a star configuration. The following modules communicate on the class 2 serial data line:

• The body control module (BCM)

• The communication interface module (OnStar®), w/UE1

• The digital radio receiver (DRR), w/U2K

• The driver door module (DDM)

• The driver seat module (DSM), w/AAB

• The DVD player

• The electronic brake control module (EBCM)

• The engine control module (ECM), w/5.3L

• The HVAC control module

• The HVAC control module - rear auxiliary

• The inflatable restraint sensing and diagnostic module (SDM)

• The instrument panel cluster (IPC)

• The liftgate control module (LGM)

• The passenger door module (PDM)

• The powertrain control module (PCM), w/4.2L

• The radio

• The transfer case shift control module (TCSCM), w/4WD

• The theft deterrent control module (VTD), w/BAE

DTC Descriptor
This diagnostic procedure supports the following DTC:

DTC U1000 Class 2 Data Link Malfunction

Conditions for Running the DTC
• Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.

• DTCs U1300, U1301, or U1305 do not have a current status.

• The vehicle power mode requires serial data communication to occur.

Conditions for Setting the DTC
A node alive message has not been received from an unidentified module within the last 5 seconds after establishing class 2 serial data communication.

Action Taken When the DTC Sets
The module uses a default value for the missing parameter.

Conditions for Clearing the DTC
• A current DTC clears when the malfunction is no longer present.

• A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids
When a malfunction occurs while modules are communicating, a lost communication DTC is set as a current DTC. When the modules stop communicating the current lost communication DTC is cleared but the history DTC remains. When the modules begin to communicate again, the module with the open fuse will not be learned by the other modules so U1000 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only U1000 is set.

Test Description
The numbers below refer to the step numbers on the diagnostic table.

A DTC U1001-U1254 Lost Communications with XXX with a history status may indicate the cause of U1000.

The modules not communicating are the likely cause of U1000. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.

The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001-U1254 Lost Communications with XXX for those modules that it was monitoring.

The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.

If all modules are communicating, the module which set U1000 may have done so due to some other condition.

The module which set U1000 is the likely cause of the malfunction.

Step
Action
Yes
No

Schematic Reference: Data Communication Schematics

Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views

1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle

2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Record the DTCs set in by each module. If using a Tech 2, use the class 2 DTC Check feature to determine which modules have DTCs set.
Did you record any DTCs in the range of U1001-U1254 with a history status?
Go to Step 3

3
Turn ON the ignition, with the engine OFF.
Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the class 2 Message Monitor feature.
Record all of the modules communicating on the class 2 serial data circuit.
Compare the list of modules which are communicating to the list given in Circuit Description.
Does any module on the class 2 serial data circuit not communicate?
Go to Step 4
Go to Step 13

4
Test the following circuits of the module that is not communicating for an open or short to ground:

• The battery positive voltage supply circuits

• The switched battery positive supply circuits

• The battery positive voltage output circuits

• The ignition voltage input circuits

• The ignition voltage output circuits

Refer to the following:

• Control Module References for applicable schematics

• Circuit Testing

• Wiring Repairs

Did you find and correct the condition?
Go to Step 9
Go to Step 5

5
Turn OFF the ignition.
Test the ground circuits of the module that is not communicating for an open. Refer to the following:
• Control Module References for applicable schematics

• Circuit Testing

• Wiring Repairs

Did you find and correct the condition?
Go to Step 9
Go to Step 6

6
Important: Inspect all connectors in the serial data communications circuit.

Refer to the following:

• Data Communication Schematics

• Testing for Intermittent Conditions and Poor Connections

• Connector Repairs


Turn OFF the ignition.
Test the class 2 serial data circuits of the module that is not communicating for an open. Refer to the following:
• Data Communication Schematics

• Circuit Testing

• Wiring Repairs

Did you find and correct the condition?
Go to Step 9
Go to Step 8

7
Inspect the harness connector of the module that is not communicating for poor connections and terminal tension at the following circuits:

• The battery positive voltage input circuits

• The switched battery positive voltage supply

• The battery positive voltage output circuits

• The ignition voltage input circuits

• The ignition voltage output circuits

• The ground circuits

• The class 2 serial data circuits

Refer to the following:

• Control Module References for applicable schematics

• Testing for Intermittent Conditions and Poor Connections

• Connector Repairs

Did you find and correct the condition?
Go to Step 9
Go to Step 8

8
Replace the module that is not communicating. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?
Go to Step 11
--

9
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Select the Display DTCs function for the module which was not communicating.
Does the scan tool display any DTCs which do not begin with a "U"?
Go to Diagnostic Trouble Code (DTC) List - Vehicle
Go to Step 10

10
Use the scan tool in order to clear the DTCs.

Did you complete the action?
Go to Step 11
--

11
Select the Display DTCs function for the modules which had U1000 set as a current DTC.

Does the scan tool display DTCs which do not begin with a "U"?
Go to Diagnostic Trouble Code (DTC) List - Vehicle
Go to Step 12

12
Use the scan tool in order to clear the DTCs.

Did you complete the action?
System OK
--

13
Did you record any other DTCs for the modules which had U1000 set as a current DTC?
Go to Diagnostic Trouble Code (DTC) List - Vehicle
Go to Step 14

14
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Use the scan tool in order to clear the DTCs.
Turn OFF the ignition for at least 5 seconds.
Turn ON the ignition, with the engine OFF.
Select the Display DTCs function.
Does the scan tool display U1000 set as a current DTC?
Go to Step 15
Go to Diagnostic Aids

15
Replace the module which had U1000 set as a current DTC. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?
System OK
 

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This is all I could find for U1016

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DTC U1001-U1254
Table 1: The Control Module ID

Circuit Description
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for state of health (SOH) monitoring/node alive messages. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that modules node alive message. Each module on the class 2 serial data circuit is required to send a node alive message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a DTC U1XXX. XXX is equal to the 3-digit identification number of the module.

The control module ID number list provides a method for determining which module is not communicating. A module with an internal class 2 serial data circuit malfunction or which loses power during the current ignition cycle would have a lost communication DTC set by other modules. Use the control module ID number list in order to determine which module is not communicating and the lost communications with XXX diagnostic table in order to diagnose the malfunction. When no message is detected from a learned identification number for 5 seconds, a DTC U1XXX is set.

The Control Module ID Control Module
ID Number

Powertrain/Engine Control Module (PCM/ECM)
016, 017

Transfer Case Shift Control Module (TCSCM)
026

Electronic Brake Control Module (EBCM)
041

Body Control Module (BCM)
064

Inflatable Restraint Sensing and Diagnostic Module (SDM)
088

Instrument Panel Cluster (IPC)
096

Radio
128

DVD Player
133

Digital Radio Receiver (DRR)
137

Communication Interface Module (OnStar®)
151

HVAC Control Module
152

Driver Door Module (DDM)
160

Passenger Door Module (PDM)
161

Liftgate/Endgate Control Module (LGM/EGM)
162

Driver Seat Module (DSM)
166

HVAC Control Module - Rear Auxiliary
167

Power Roof Module (PRM)
173

Theft Deterrent Control Module (VTD)
192


When more than one loss of communication DTC is set in a single module or among multiple modules, diagnose the DTCs in the following order:

Current DTCs before history DTCs except as specified in the diagnostic tables.
The DTC which is reported the most times.
From the lowest number DTC to the highest number DTC.
Conditions for Running the DTC
• Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.

• DTCs U1300, U1301 or U1305 do not have a current status.

• The vehicle power mode requires serial data communication to occur.

Conditions for Setting the DTC
A node alive message has not been received from an identified module within the last 5 seconds.

Action Taken When the DTC Sets
The module uses a default value for the missing parameter.

Conditions for Clearing the DTC
• A current DTC clears when the malfunction is no longer present.

• A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids
• Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios:

- A control module on the data communication circuit was disconnected while the communication circuit is awake.

- Power to one or more modules was interrupted during diagnosis.

- A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold.

- Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time.

- If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.

• A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.

• Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.

• Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.

• Use to determine if the module uses high or low speed GMLAN serial data communications.

• Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control module.

• This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to, providing the vehicle is equipped with the control module.

Test Description
The number below refers to the step number on the diagnostic table.

The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.

Step
Action
Yes
No

Schematic Reference: Data Communication Schematics

Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views

1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle

2
Important: Use the control module ID number list in order to determine which module is not communicating.

Test the following circuits of the module that is not communicating for an open or a short to ground:

• The battery positive voltage input circuits

• The battery positive voltage output circuits

• The ignition voltage input circuits

• The ignition voltage output circuits

• The switched battery positive voltage circuits

Refer to the following:

• Control Module References for applicable schematics

• Circuit Testing

• Wiring Repairs

Did you find and correct the condition?
Go to Step 7
Go to Step 3

3
Turn OFF the ignition.
Test the ground circuits of the module that is not communicating for an open.
Refer to the following:

• Control Module References for applicable schematics

• Circuit Testing

• Wiring Repairs

Did you find and correct the condition?
Go to Step 7
Go to Step 4

4
Test the class 2 serial data circuits of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?
Go to Step 7
Go to Step 5

5
Inspect the harness connectors of the module that is not communicating for poor connections and terminal tension at the following circuits:

• The battery positive voltage input circuits

• The battery positive voltage output circuits

• The ignition voltage input circuits

• The ignition voltage output circuits

• The switched battery positive voltage supply circuits

• The ground circuits

• The class 2 serial data circuits

Refer to the following:

• Control Module References for applicable schematics

• Testing for Intermittent Conditions and Poor Connections

• Connector Repairs

Did you find and correct the condition?
Go to Step 7
Go to Step 6

6
Replace the module that is not communicating. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?
Go to Step 7
--

7
Install a scan tool.
Turn ON the ignition with the engine OFF.
Select the Display DTCs function for the module which was not communicating.
Does the scan tool display any DTCs which do not begin with a "U"?
Go to Diagnostic Trouble Code (DTC) List - Vehicle
Go to Step 8

8
Select the Display DTCs function for the modules which had the Loss of Communications DTC set.

Does the scan tool display any DTCs which do not begin with a "U"?
Go to Diagnostic Trouble Code (DTC) List - Vehicle
Go to Step 9

9
Use the scan tool in order to clear the DTCs.
Continue diagnosing or clearing the DTCs until all the modules have been diagnosed and all the DTCs have been cleared.
Did you complete the action?
System OK
 

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DTC P0455

DTC P0455
Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC P0455: Evaporative Emission (EVAP) System Large Leak


Circuit/System Description
The control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge solenoid valve OPEN and the EVAP vent solenoid valve CLOSED . This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge solenoid valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent solenoid valves.

Control Module Command
EVAP Canister Purge Solenoid Valve
EVAP Canister Vent Solenoid Valve

ON
Open
Closed/Not Venting

OFF
Closed
Open/Venting


Conditions for Running the DTC
• DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0128, P0443, P0449, P0452, P0453, P0502, P0601, P0602, P0606, P0641 are not set.

• The engine is running.

• The ignition voltage is between 11-18 volts.

• The barometric pressure (BARO) is more than 74 kPa.

• The fuel level is between 15-85 percent.

• The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F).

• The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).

• The start-up ECT and IAT are within 8°C (14.4°F) of each other.

• DTC P0455 runs once per cold start within 10 minutes of start-up.

Conditions for Setting the DTC
The EVAP system is not able to achieve or maintain vacuum for up to 4 times during the diagnostic test.

Action Taken When the DTC Sets
• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
• A loose, missing, incorrect, or damaged fuel fill cap may cause this DTC to set.

• To help locate intermittent leaks, use the J 41413-200 to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light . Introducing smoke in 15-second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.

• To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT .

• Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

• For intermittent conditions, refer to Testing for Intermittent Conditions and Poor Connections .

Reference Information
Schematic Reference

• Evaporative Emissions Hose Routing Diagram

• Engine Controls Schematics


Connector End View Reference

• Powertrain Control Module Connector End Views

• Engine Controls Connector End Views


Electrical Information Reference

• Circuit Testing

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

• Scan Tool Data List

• Scan Tool Output Controls


Special Tools Required

• CH-48096 EVAP Service Access Port Tool

• GE-41415-50 Fuel Tank Cap Adapter

• J 41413-200 Evaporative Emission System Tester (EEST)

• J 41413-SPT High Intensity White Light


Circuit/System Testing
Important:

• Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize.

• Refer to the J 41413-200 operation manual for detailed instructions.


Using the GE-41415-50 , connect the J 41413-200 to the vehicle filler neck.
Seal the system and use the flow meter on the J 41413-200 , calibrated to 0.51 mm (0.02 in) to determine that there is no leak in the EVAP system.
⇒ If a leak is detected, use the J 41413-200 to apply smoke to the EVAP system at the EVAP service port or the filler neck until the leak is located. For vehicles without a service port, disconnect the purge tube at the quick connector on the EVAP canister side of the purge solenoid valve and install the CH-48096 .

Start the engine with the J 41413-200 connected to the fuel filler neck.
Allow the engine to idle.
Use the Purge/Seal function to seal the system with a scan tool.
Command the EVAP canister purge solenoid valve to 20 percent.
The vacuum/pressure gage on the J 41413-200 and the FTP parameter on the scan tool should both show vacuum.
⇒ If the vacuum/pressure gage on the J 41413-200 does not show vacuum, check for a restricted purge path.

Vacuum should increase on the gage of the J 41413-200 and scan tool until it reaches approximately 16 inches H2O, or until the vacuum reaches the abort limit on the scan tool.
⇒ If the difference between the FTP parameter on a scan tool and the vacuum/pressure gage on the J 41413-200 was more than 1 inch, replace the FTP sensor.

⇒ If the maximum Fuel Tank Pressure Sensor parameter on a scan tool display was less than 3.2 volts, replace the FTP sensor.

Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Fuel Tank Pressure Sensor Replacement

• Control Module References for powertrain control module (PCM) replacement, setup, and programming

• Evaporative Emission System Cleaning
 

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2007 isuzu ascender
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76 Posts
Discussion Starter #9
You Rock!!

Thanks 07TB!! You're full of information. This is of great help and I can't wait to get started. I'll schedule an appointment for the ECBM reprogram. :thx

:grouphug::woohoo:
 

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2006 gmc envoy_denali
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21 Posts
This explains my horn problem as well. It was intermittent so I swapped out the fuse and relay with no luck, and now it's not really intermittent anymore. It just doesn't work at all. I turned the setting for the horn with the keyless entry off, so I guess I'll have to turn that back on and try that to make sure this is the same thing.

With regards to TSBs, will the dealers perform them for free if a vehicle is out of warranty? I have a 06 Envoy Denali that is out of warranty.

Thanks for the help. For some reason most dealers I have any experience with don't know about these TSBs and I always have to bring in the text of the thing before they believe me that a bulletin was even issued. Why are they so ignorant?
 

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2007 chevy trailblazer_ls
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1,239 Posts
With regards to TSBs, will the dealers perform them for free if a vehicle is out of warranty? I have a 06 Envoy Denali that is out of warranty.

Thanks for the help. For some reason most dealers I have any experience with don't know about these TSBs and I always have to bring in the text of the thing before they believe me that a bulletin was even issued. Why are they so ignorant?
The short answer is no, they won't do a TSB for a vehicle out of warranty. If it was a safety or emissions related issue, maybe. But I guess you could explain that a horn that doesn't work is a safety concern.

For them not knowing about TSB's there are literly hundreds of them for each vehicle and each model year. Years ago, GM issued paper TSBs that each technician got a copy. There are just too many (and too expensive) to print them. Usually, a TSB search is one of my first steps for diagnosis.
 

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2009
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1,088 Posts
This explains my horn problem as well. It was intermittent so I swapped out the fuse and relay with no luck, and now it's not really intermittent anymore. It just doesn't work at all. I turned the setting for the horn with the keyless entry off, so I guess I'll have to turn that back on and try that to make sure this is the same thing.

With regards to TSBs, will the dealers perform them for free if a vehicle is out of warranty? I have a 06 Envoy Denali that is out of warranty.

Thanks for the help. For some reason most dealers I have any experience with don't know about these TSBs and I always have to bring in the text of the thing before they believe me that a bulletin was even issued. Why are they so ignorant?
From my experience and from what I have read if you are out of warranty then you pay for repairs. TSB's are just info that GM has gathered to help the service tech diagnose an issue. It is not a like a recall.
 

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2006 gmc envoy_denali
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21 Posts
It's certainly a safety issue to me, as it hasn't worked when I need it with all these crazy drivers on the snowy, icy roads. I've been run off into the shoulder a couple times and I'm tired of it not being there when I need it. I doubt I'll win that argument given the car company's situations these days though. At least it's explained though, because I was scratching my head trying to figure out what I hadn't done in troubleshooting.
 

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2007 isuzu ascender
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76 Posts
Discussion Starter #14
Horn Fixed

I got a chance to remove the airbag and steering wheel last night. I found there was a tiny white plastic tab that broke off from the horn contact retainer tube. It had fallen down in between the copper contacts. :duh:It was pretty easy and only took about 15 mins, that is, after the 30 min battery disconnect to power down the SRS system. Here are a few pictures - sorry, I had to use my camera phone. the horn contact tube I mentioned is on the left side of the steering wheel nut (where the two red wires connect):rotfl:.

Step 1: disconnect battery for 30 mins minimum
Step 2: use two small objects ( I used allen wrenches) in the small holes on the side of the steering wheel (not the shroud). Push in, toward the center of the wheel to dislodge the airbag assembly.
Step 3: Lift the bag slightly and remove the two connectors at the end of the yellow wires.
Step 4: Make sure the copper contacts (2) are free of corrosion.
Step 5: I pushed in and twisted the white tube 1/2 turn (to the left of the steering wheel nut) to dislodge the horn contact tube.
Step 6: Pulled the steering wheel off, didn't need a puller. It may not be necessary, but it was easier to find the plastic piece that was stuck in the hole. Be careful when replacing the wheel, the splines are keyed.
Good luck!
 

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2006 chevy trailblazer_lt
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7 Posts
first post had this problem

i see this is an old topic but for what its worth everylittle bit helps.
here is a video from jegs(grant wheel replacement) for the do it you're selfers.i had this horn problem.it basically shows how to remove airbag etc.if to get at the horn contacts to clean or replace.good luck.
not sure if i can post the link but all you have to do is Google
"grant revolution" should be the first link to jegs .
 

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2008 chevy trailblazer_lt
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1 Posts
I see this is an old thread, but I too had the same intermittent horn issues with my 2008 Trailblazer for about a year. It would sometimes work by pushing the steering wheel pad but was weak sounding on occasion. It completely quit working this month from the steering wheel and key fob. Based on the thread I tested all components of the system. Fuse and relay were fine and there were no issues under the steering wheel pad. I decided on a whim to take out the wire connection at the horn, clean it , apply some dyelectric grease and snug it back in. That fixed the problem. The horn now functions normally under all conditions including locking the doors with the fob, pushing the panic button and pushing the pad on the steering wheel. In all threads I viewed across the net, I had not seen this as a solution to the problem. Sometimes when all else fails try the simple stuff and in this case it worked.
 

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2005 gmc envoy_slt
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95 Posts
I got a chance to remove the airbag and steering wheel last night. I found there was a tiny white plastic tab that broke off from the horn contact retainer tube. It had fallen down in between the copper contacts. :duh:It was pretty easy and only took about 15 mins, that is, after the 30 min battery disconnect to power down the SRS system. Here are a few pictures - sorry, I had to use my camera phone. the horn contact tube I mentioned is on the left side of the steering wheel nut (where the two red wires connect):rotfl:.

Step 1: disconnect battery for 30 mins minimum
Step 2: use two small objects ( I used allen wrenches) in the small holes on the side of the steering wheel (not the shroud). Push in, toward the center of the wheel to dislodge the airbag assembly.
Step 3: Lift the bag slightly and remove the two connectors at the end of the yellow wires.
Step 4: Make sure the copper contacts (2) are free of corrosion.
Step 5: I pushed in and twisted the white tube 1/2 turn (to the left of the steering wheel nut) to dislodge the horn contact tube.
Step 6: Pulled the steering wheel off, didn't need a puller. It may not be necessary, but it was easier to find the plastic piece that was stuck in the hole. Be careful when replacing the wheel, the splines are keyed.
Good luck!
:iagree:

I would check this before anything....same thing happened to mine. Worked intermittently and then it completely stopped. Easy fix and it only cost me 20 bucks in parts at the dealer. I never waited to let the SRS power down (pulled airbag many times to put led's in the steering wheel buttons)...I just pulled the airbag fuse and negative lead on the battery and simply just be careful with it. Still expensive for a piece of plastic though
 
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