Fuel Injectors Have to Be Replaced Along with PCM Firmware Upgrade?? - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 4 (permalink) Old 04-20-2010, 09:42 PM Thread Starter
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Fuel Injectors Have to Be Replaced Along with PCM Firmware Upgrade??

CEL on with p1174 code.

I've been having this problem for a while. Engine will throw the P1174 code, then it'll disappear for a day, throw it again, a couple times, and then it'll just disappear for several weeks.

TSB Document ID# 2046855
2006 Chevrolet Cobalt

This describes the problem, and says its a case of bad injectors and faulty PCM code. They say replacing injectors will result in further codes without a PCM tune.

Do you think I could just install my own injectors and then have them re-calibrate the PCM for fuel balance?

Think power train warranty covers this? Gas is inline with power train is it not?
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post #2 of 4 (permalink) Old 05-10-2010, 06:41 AM
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i'd love the answer to this as well...same problem.
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post #3 of 4 (permalink) Old 05-10-2010, 07:12 AM
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I sure would try to get it under the power train. does not sound like a fun or cheap fix.

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post #4 of 4 (permalink) Old 05-10-2010, 11:11 AM
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Info found from quick search:


Heres what it says about the p1174

The Fuel Trim Cylinder Balance diagnostic detects a rich or a lean cylinder-to-cylinder air/fuel ratio imbalance. The diagnostic monitors the pre-catalyst heated oxygen sensor (HO2S) signal's frequency and amplitude characteristics by calculating an accumulated voltage over a predetermined sample period. An imbalance is indicated when multiple samples of the accumulated voltage are consistently higher than the desired value.

Heres some things you can check.

•Inspect the air induction system for modified, damaged, leaking, or restricted components.
•Inspect the crankcase ventilation system for improper operation.
•Inspect the vacuum hoses for splits, kinks, and improper connections.
•Inspect for vacuum leaks at the intake manifold, the throttle body, and the injector O-rings.
•Test for a restricted, damaged, leaking, or modified exhaust system from the catalytic converter forward. Refer to Symptoms - Engine Exhaust .
•Test the fuel injectors for improper operation. Refer to Fuel Injector Diagnosis .
•Test for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
•Test for excessive fuel in the crankcase due to leaking injectors.
•Test the ignition system for improper operation. Refer to Electronic Ignition (EI) System Diagnosis .
•Test the engine for any mechanical conditions such as sticking valves, lifters, etc., which could alter the flow into the combustion chamber


Also the Map sensor could be reading incorrectly or the O2 sensor.

Found this as well

SES Light With No Engine Performance Concerns And A P1174 DTC - Reprogram ECM - keywords calibration CEL ECM light MIL PCM repeat SES #PIP3968

On rare occasions, a SES light may be experienced with no engine performance concerns and a P1174 DTC. This PI does not apply if there are any engine performance concerns or other engine performance DTCs, such as a P0300.

Recommendation/Instructions:
If the SI diagnostics do not isolate a cause for this concern, reprogram the ECM with the latest engine calibration. At this time, the latest engine calibration are titled "new calibration with diagnostic enhancements for DTCs P1682 and P1516 and fix for stall immediately after remote start", This calibration, or any that follow, is designed to address this concern.

THis to

SES Light Due To A P1174 DTC - Perform Injector Test With AFIT - CH47976 - keywords active balance cylinder engine fuel injector lamp light misfire miss P0300 test tester #PIP4017A - (01/18/2007)

Condition/Concern:
On rare occasions, a SES light may be encountered due to a P1174 DTC. In some instances, a P0300 may also be stored. This may be due to a fuel injector concern on one of the cylinders that a Tech 2 fuel injector balance test may not isolate.

Recommendation/Instructions:
If the SI diagnostics do not isolate a cause for this concern, use the Active Fuel Injector Tester (AFIT - CH47976) to perform an "Injector Test" as outlined in the AFIT User Guide. The AFIT "Injector Test" measures the flow characteristics of all fuel injectors, which is more precise when compared with the standard Tech 2 fuel injector balance test. As a result, the AFIT is more likely to isolate the cause of a P1174 DTC if it is being caused by a fuel injector concern.. The CH-47976 (Active Fuel Injector Tester - AFIT) can also be used to measure fuel pressure and fuel system leak down.

Also, as mentioned in the P1174 SI diagnosis, if the misfire current counters or misfire graph indicate any misfires, it may be an indicator of the cylinder that is causing the concern.
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