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2005 Chevy Avalanche Check Engine Light Flashes Intermittently - No Diagnostic Codes

Model: 2005 Chevy Avalanche Fault Code: P0171 Posted: 2018-03-27 17:20

I own a 2005 Chevrolet Avalanche and am experiencing an intermittent Check Engine Light issue. When I turn the key on without starting the vehicle after it has been idle for some time, the Check Engine Light illuminates. However, if I start the vehicle and then turn it off, turning the key on again without starting results in the light not coming on. After allowing the vehicle to sit for about a minute (no precise timing), turning the key on once more causes the Check Engine Light to illuminate again. This behavior is inconsistent and occurs only under specific conditions. The instrument cluster functions normally—cigarette lighter outlets work, and there are no other dashboard issues. I've checked all fuses, replaced them as a precaution, and confirmed that my scanner shows no stored diagnostic trouble codes (DTCs) when connected to the vehicle. Despite this, the Check Engine Light activates intermittently under certain key-on conditions. I am unable to pass emissions inspection until this issue is resolved and would greatly appreciate any insights or troubleshooting steps from experienced owners or technicians.

Related fault codes
P0171P0172
Comments (5)
Anonymous 2018-03-27 22:28

When the ignition is on and the Check Engine Light is off, does your scanner communicate properly with the Engine Control Module (ECM)?

Anonymous 2018-03-28 07:29

Yes, our scanner consistently communicates with the 2005 Chevy Avalanche's ECM—no connectivity issues are present.

Anonymous 2018-03-28 08:31

Verify the voltage at the Powertrain Control Module (PCM) from the instrument cluster. The PCM is responsible for grounding the Check Engine Light. A reference wiring schematic can be found on BBBind.com.

Anonymous 2018-03-28 08:55

It's essential to verify the ignition feed to the Instrument Panel Controller (IPC). Use a test light between the ignition power circuit and the MIL control circuit at the IPC while the key is in the 'on' position. If the light does not illuminate when the IPC is disconnected, this may indicate a high-resistance connection, faulty wiring, or a defective IPC or PCM. If you have consistent voltage and the test light shows continuity with the IPC unplugged, then the IPC itself is likely faulty. I can share detailed wiring diagrams from my own vehicle's system if needed—please email me directly.

Anonymous 2018-10-02 12:17

I'm wondering if you've ever identified the root cause of this issue—I have a 2004 Chevrolet Silverado 1500 Z71 with a 5.3L V8 engine that's also experiencing intermittent battery drain problems, which may be related to electrical system faults.