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2004 chevy trailblazer_ls
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Discussion Starter · #1 ·
Got my new ECU from PCM4Less in the other day, popped it in. I went out and did the case re-learn instructions posted elsewhere. Followed them to a T, no issues. Truck runs great, no check engine light either.


So I go in today to get it re-smogged....sorry, failed again. Says 2 out of the 8 OBD2 readiness checks are not complete. Evap/purge and Converter. I've put about 60-70 miles on this thing already, how much further must I drive it?
 

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2004 gmc
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Many items aren't time or miles, but as you titled it: drive cycles. With an overnight or multi-hour cool-down in between a good hot run. I think the EPA says you have to drive the vehicle long enough to raise the coolant temperature at least 40 degrees F, and the startup temperature needs to be less than 160 degrees F. So short stops won't do it.

One site says:
The OBDII drive cycle begins with a cold start (coolant temperature below 122 degrees F and the coolant and air temperature sensors within 11 degrees of one another).
 

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Discussion Starter · #3 ·
Updated my other thread, but now the truck is showing a P0128 code. Temp too low?

Temp is rock solid at 210, thermo has already been changed. Truck has 77K on it.
 

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If the coolant sensor was bad, your gauge wouldn't read a nice 210. If the thermostat was bad, the reading would be low. Since it's not likely to be a bad sensor and a bad gauge, I can't explain it. How many drive cycles have you gone through so far?

The SES light should go out after three good cycles. The code won't get cleared from the HISTORY section for 40 cycles. Can your scanner distinguish between current and history codes?
 

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Discussion Starter · #5 ·
don't have a scanner, just borrowing the one from zone or orielly auto when needed.

CEL came on this AM while driving around town, with the gauge at 210 (Maybe a smidge below the line).

Not sure on how many cycles I've been on, maybe 4-5 trips since installing the new PCM from PCM4less.
 

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Discussion Starter · #6 ·
Getting tired of this, but I supposed I'm still ahead of dropping it off at the dealer.

Bought an innova 3160, should tell me all the info I need, and it does ABS (should i ever have that problem in the future).

I'm really interested to see if the ECT temp is lower than the gauge reports. Wife told me today it was on the tick mark just under 210. Perhaps the gauge says 210 but it's in the 160 range which set off the P0128 code.
 

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The tick mark UNDER 210 probably does mean the raw unfiltered data could be as low as 170. The trigger point for P0128 is less than 176 F after driving long enough that it should be hotter.
 

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Discussion Starter · #8 ·
Thanks man. Yup, tonight on the way home from work after 10 mins it was still 2 marks under 210. Only after I had to stop at a red light did the temp finally get to 210. After I started moving again it came back down to one mark under 210.

I NEVER remember it doing this before the PCM from PCM 4 less.
 

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Discussion Starter · #9 ·
Re-replaced thermo, and did the coolant temp sensor while I was in there. Temp is 210 or above now quickly, have put about 60 miles on it so far, no CEL.

Hopefully that innova 3160 I ordered will come in handy in the future, hopefully for now I've got this thing figured out.
 

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2007 chevy trailblazer_ss_1ss
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Just so you know, because of the SES light, the drive cycle started over. You can read the I/M Readiness with a scan tool so you don't have to waste a trip for them to tell you it isn't ready. As long as all the other tests have passd, you don't need the EVAP test to pass. Catalyst is the main one, once that one runs and passes, you'll hass the emissions test. Search Google for "OBD 2 Drive Cycle" and you will find instructions of exactly what to do to get all of the tests to run.
 

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Drive Cycle

The OBD II Home Page - On-Board Diagnostic System Information
Autotap® OBDII Diagnostic Scanner

General Motors Driving Cycle

A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle do the following:
•Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.

2.Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.

3.Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.

4.Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.

5.Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.

6.Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.

7.Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.

8.Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

Reprinted on OBDII web site courtesy of General Motors Corporation
© General Motors Corporation

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