GM 2.4L Help - 2007 Cobalt - Random P1174 Code "Fuel Trim Cylinder Imbalance"

[spankis]

My girlfriend drives a 2007 Cobalt SS NA 2.4L, and it's been a pretty good car for her so far. It has just under 90k on it, and it has had a check engine light on and off for the last few months. The code is P1174 "Fuel Trim Cylinder Imbalance", and the car still runs great and mileage does not appear to be affected so far. From what I read this can be a ton of different things from Air Filter, O2 sensor, coils/plugs, throttle body/MAF, and lastly fuel injectors.

 

As for fuel injectors though, from what I read there was a recall or service bulletin out at one point that called for testing injectors, sometimes replacing them under warranty, and following up the replacement injectors with an updated ECM flash. Obviously the car is now out of warranty.

 

I'm hoping somebody is somewhat familiar with this issue, as I don't want to just throw parts at it. I'm capable of replacing everything fuel or ignition related, but I'm not sure how to go about testing injectors and whatnot, and I would obviously need to see the dealer for an ECM flash if required. Any tips are appreciated.

[Cordell]

If it's fuel injectors you'd need GM's scan tool to do a flow test. If it was an issue they may have created a special policy to extend the warranty on the effected parts. I'm not sure about any of that since I never really saw many 2.4L ecotecs (not common compared to the 2.2L) You may want to contact the dealer with the VIN and tell them you may have this issue is there anything still covered for the car. If they quickly tell you know call someone who will run the VIN and give you the status of the car. Besides that it's not very far out of powertrain warranty you might be surprised what happens if you bitch loud enough.

 

Otherwise I would be checking the injectors, and without a proper scan tool to test them in the car you'll be taking them to somebody to bench test them. I've never had to send any out for this, and I don't work at a GM dealer anymore to offer much more help. If somebody has access to a tech 2 it's a 5 minute test with the scanner and a pressure gauge.

[spankis]

Thanks sir, all of that is helpful. I will start with some phone calls after work tomorrow (today).

[spankis]

I found this TSB:

 

Document ID# 2046855

2006 Chevrolet Cobalt

 

 

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Subject: Check Engine Light On, DTCs P0171, P0300, P1174 Set (Perform Injector Test/Replace Injectors and Reprogram ECM, if Necessary) #08-06-04-001 - (01/02/2008)

 

 

 

Models: 2006-2007 Chevrolet Cobalt, HHR

 

2007 Pontiac G5, G6

 

2006-2007 Saturn ION

 

with 2.4L Engine (VIN B, P - RPO LE5)

 

 

 

 

--------------------------------------------------------------------------------

 

Condition

Some customers may comment on the check engine light being illuminated.

 

A scan tool may reveal DTC P0171, P0300 or P1174 set as current or in history.

 

Cause

This condition may be caused by the plugging of one or more of the injector director plate orifices which results in a lean condition.

 

Correction

Important: This condition cannot be corrected by cleaning the injector(s).

 

Perform an injector balance test using the Active Fuel Injector Tester (AFIT), CH-47976. Refer to the Fuel Injector Diagnosis (w/CH47976) procedure in SI. If any injector is identified as having a lean condition, replace all four injectors with the revised injectors. After installing the new injectors, reprogram the ECM with updated calibration files using the TIS2WEB Service Programming System (SPS) application. There are two calibration part numbers that are valid for "Engine Operation". Select the part number with the description that reads for vehicles with second design injector. The injector has a dark blue overmold color for this repair.

 

Important: The fuel injectors must be replaced and the new calibration files must be installed to ensure a complete repair. Failure to perform both repairs will result in the customer returning with the same condition.

 

If a vehicle returns with the same condition after having this repair performed, the technician should first verify that the complete repair was performed before continuing with SI diagnostics.

 

Parts Information

Part Number

Description

Qty

 

12602480

Injector, Fuel

4

 

 

Warranty Information

Important: For claims to be paid, injector balance test results must be recorded on the repair order.

[spankis]

I also just called Chevrolet customer care, and explained the issue and noted the TSB above. They are not agreeing to cover any parts out of warranty, but have agreed to waive the $90 diagnosis fee through Taylor Chevrolet in Lancaster.

 

From what I understand they will run the injector balance test to confirm or deny the injectors as the culprit. If they are I'll likely replace them myself, but I'm assuming they will expect me to pay to flash the calibration files listed above after I install the new "second design" injectors. Is this calibration flash something that could be done through someone with a TECH-2 or am I stuck with the dealer?

[Cordell]

I also just called Chevrolet customer care, and explained the issue and noted the TSB above. They are not agreeing to cover any parts out of warranty, but have agreed to waive the $90 diagnosis fee through Taylor Chevrolet in Lancaster.

 

From what I understand they will run the injector balance test to confirm or deny the injectors as the culprit. If they are I'll likely replace them myself, but I'm assuming they will expect me to pay to flash the calibration files listed above after I install the new "second design" injectors. Is this calibration flash something that could be done through someone with a TECH-2 or am I stuck with the dealer?

 

Sounds like you're off to a great start. You really just need someone with a GM login and access to an MDI (module diagnostic interface, GM's flash tool). I know there are some people out there in the aftermarket with the ability to reprogram, but I don't know any places like that offhand. It can be flashed with a Tech2 if someone has all the cables and internet login, but most people don't do it that way. Typically flashing is done with a newer type interface, either a dealer style or aftermarket. Aftermarket stuff for programming is out there it's just not a typical shop tool in most shops.

 

Even if you have it done at the dealer I would only expect them to charge you a half hour of labor, of course most advisors will start by trying to get you for the full hour and my response would be that book time is only 4 tenths and see their reaction.

[spankis]

More good info, thanks sir.

[spankis]

So last week Taylor Chevrolet ran the fuel injector test as listed in the TSB above, and two of the 4 injectors are bad.

 

I'm going to replace all 4 injectors myself this weekend with the GM "second design" injectors, but the required calibration file update will still need done next week. Right now I have a standing appointment Wednesday morning at Taylor Chevrolet in Lancaster to perform the update, and they are quoting $105 to do the flash.

 

Cordell, I took your advice and asked them if they were rounding up the book hours on the calibration labor, and told them I had heard it booked for .4 hours. The response I got was "any software update done with the TECH-2 is a standard 1 hour of labor". I called Jeff Wyler for a second opinion (shitty service dept. from what I hear), and got the same line of "GM warranty time even calls for 1 hour, I'm not sure who told you .4 hours...."

 

Anybody out there able to do this flash for me any cheaper with a TECH-2? Just trying to save the GF some money if possible.

 

Thanks

[Cordell]

So last week Taylor Chevrolet ran the fuel injector test as listed in the TSB above, and two of the 4 injectors are bad.

 

I'm going to replace all 4 injectors myself this weekend with the GM "second design" injectors, but the required calibration file update will still need done next week. Right now I have a standing appointment Wednesday morning at Taylor Chevrolet in Lancaster to perform the update, and they are quoting $105 to do the flash.

 

Cordell, I took your advice and asked them if they were rounding up the book hours on the calibration labor, and told them I had heard it booked for .4 hours. The response I got was "any software update done with the TECH-2 is a standard 1 hour of labor". I called Jeff Wyler for a second opinion (shitty service dept. from what I hear), and got the same line of "GM warranty time even calls for 1 hour, I'm not sure who told you .4 hours...."

 

Anybody out there able to do this flash for me any cheaper with a TECH-2? Just trying to save the GF some money if possible.

 

Thanks

 

Trust me the techs get paid .4 hours under warranty. We typically rounded it up for customer pay, but they likely want to be difficult because you aren't doing the "whole job" with them. Good luck getting that taken care of.