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2002 chevy trailblazer_lt
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Discussion Starter · #1 ·
Just got my very own 2002 Trailblazer a few weeks ago. I took it out camping for the first time last weekend, driving on plenty of dirt roads and using the recently repaired 4x4. On the way home from the trip, I was driving down a canyon and ran into a mean thunderstorm with really heavy rain. After driving in the crazy rain for ten minutes, my service engine soon (SES) and reduced engine power (REP) lights both came on and the engine power was suddenly really bad. I could also suddenly hear a whurring noice that sounded like my fan clutch was stuck on, but my engine temp was below 210. I pulled off at a rest stop and waited for the rain to stop then let the car sit for about a half hour. When I got back in, the REP light was off but SES light was still on. Later in the evening, I took the car to a friend's house and the SES light went off. I haven't driven it much since then but it seems fine now.
I was thinking that maybe a sensor got wet. Is this likely? If not, what could have caused this?
 

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2004 gmc
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There should still be a code in memory. If you read that, it would help a LOT to solve the mystery.

REP usually comes from a bad reading of the accel pedal position sensors, the throttle body sensors, or the fan clutch RPM. None of those are in a position to get really wet except maybe the fan clutch harness.

Let us know what a scan tool says about the stored code. REP events usually store freeze frame data for an advanced scan tool to get at.
 

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2004 gmc envoy_slt_xuv
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You may also find the following SB of interest..Photos didn't copy..
Covers water leaking onto the engine from windshield wiper area in front of windshield from under the hood. They have a new seal to install, now. The leaking water can "short out" the ignition on some cylinders:





Bulletin No.: 06-06-04-048B

Date: January 12, 2007

TECHNICAL
Subject:
4.2L LL8 Engine - Flashing and/or MIL/SES Light, Rough Idle, Misfire(s) DTC(s) P0300, P0301, P0302, P0303, P0304, P0305, P0306 (Install AIP Seal)
Models:
2004-2007 Buick Rainier
2002-2007 Chevrolet TrailBlazer
2002-2007 GMC Envoy
2002-2004 Oldsmobile Bravada
2005-2007 Saab 9-7X

with Vortec(TM) 4.2L Inline 6 Cylinder Engine (VIN S - RPO LL8)

Supercede:

This bulletin is being revised to add the new part numbers for the Spark Plugs and Ignition Coils. Please discard Corporate Bulletin Number 06-06-04-048A (Section 06 - Engine/Propulsion System).

Condition

Some customers may comment that, after severe weather that includes large amounts of rain in a short period of time, the engine has a rough idle and/or flashing MIL/SES light. Upon further investigation, there may be the following DTC(s): P0300, P0301, P0302, P0303, P0304, P0305 or P0306.

This condition can be aggravated if the vehicle is parked nose down on an incline during this type of weather. The customer may also comment on repeat occurrences of this condition because water may be passing over the Air Intake Plenum (AIP).

Cause

The dripping rain water onto the engine cam cover will collect at the coil(s) and may seep past the coil(s) into the spark plug(s) well of the cylinder head and may affect the operation of the spark plug(s) and coil(s), causing the misfire(s).

Correction

Before replacing the AIP seal, refer to Misfire diagnostics in SI to determine if water intrusion was the cause of the misfire.

Diagnostic Aids for Misfire

Refer to SI for Base Engine Misfire without Internal Engine Noises.

If no trouble found (NTF) using SI document on Base Engine Misfire without Internal Engine Noises, then refer to SI for Misfire DTC(s).

If Misfire diagnostic leads to the removal of the coil(s) and spark plug(s), refer to the following SI Documents:

Air Cleaner Outlet Resonator Replacement

Ignition Coil Replacement Removal Procedure

Spark Plug Replacement

Coil(s) damage from water intrusion will have a film of white chalk build-up on the outside and inside of the spark plug boot to ignition coil(s) assembly. If present, remove the spark plug(s) and inspect for similar build-up on the outside of the spark plug(s).

If NTF with the coil(s) and spark plug(s), continue on with the Misfire Diagnostic in SI.

Replace any coil and spark plug that has been diagnosed to be damaged from water intrusion. To prevent a reoccurrence, follow repair information outlined in this bulletin to replace the AIP seal.

To prevent a repeat occurrence of the above condition, Do Not return the vehicle to the customer without replacing the AIP seal if water intrusion was determined to be the cause.

If water intrusion was determined to be the cause for the replacement of the spark plug(s) and/or coil(s), the AIP seal should be replaced.

Installation of AIP Seal

To prevent a reoccurrence, the revised AIP seal will redirect the rain water flow away from the engine cam cover area. The following repair information outlined in this bulletin will assist technicians in the replacement of the revised AIP seal.







Remove the original rear hood (AIP) seal to the air inlet grille panel staked studs. Refer to the above illustration (1).

DO NOT remove the air inlet grille panel from vehicle, Illustration purpose Only.







Cut three or four slits through the original rear hood (AIP) seal to the air inlet grille panel plastic staked studs. Carefully remove the rear hood (AIP) seal from the staked plastic studs. Do Not cut off the top or staked portion of the plastic studs holding the rear hood (AIP) seal to the air inlet grille panel. If removed, the air inlet grille panel will have to be replaced. Refer to the above illustration (1).

DO NOT remove the air inlet grille panel from vehicle, Illustration purpose Only.







Seal removed without any damage to the air inlet grille panel plastic staked studs. Refer to the above illustration (1). Remove any dirt or debris from the sealing surface of the air inlet grille panel







Install AIP seal, P/N 25788476. The revised seal has a foam weatherstrip attached to the bottom. Refer to the above illustration (1). The foam weatherstrip faces the air inlet grille panel. Carefully stretch the revised AIP rubber seal over the plastic staked studs of the air inlet grille panel without damaging them.







Parts Information

Warranty Information (excluding Saab U.S. Models)







For vehicles repaired under warranty, use the table.

Warranty Information (Saab U.S. Models)







For vehicles repaired under warranty, use the table.
 
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