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2004 Chevy Colorado P0171 Check Engine Light: Intermittent Code & Diagnosis Tips

Model: 2004 Chevy Colorado Fault Code: P0171 Posted: 2017-03-30 17:33

I recently purchased a 2004 Chevrolet Colorado one year ago, and ever since I took ownership, I've been dealing with the check engine light illuminating with code P0171. Although it didn't show up during my vehicle inspection due to driving conditions, it's been a persistent issue. After replacing the Mass Air Flow (MAF) sensor, the code typically appears when idling for more than 5 minutes. On some days, it activates during a 15-minute commute to work and then disappears afterward. The dealership where I bought the truck previously replaced the spark plugs, coil packs, and both oxygen sensors. Despite these repairs, the P0171 issue remains unresolved. I'm looking for reliable troubleshooting steps or potential causes—especially given that this code is intermittent. Any advice on where to start would be greatly appreciated.

Related fault codes
P0171
Comments (5)
Anonymous 2017-03-30 18:36

https://www.obd-codes.com/p0171 P0171 typically indicates a lean air-fuel mixture, and in most vehicles this is caused by intake manifold leaks. Since your issue is intermittent, further diagnostics are needed. Given that you've already invested significant money in repairs, the problem likely lies within the intake system—especially for vacuum leaks or loose connections.

Anonymous 2017-03-31 08:00

Is P0171 the only diagnostic code present? Is your vehicle stock (no modifications)? Consider checking fuel pressure and reviewing Fuel Trim (FT) values, as abnormal readings can point to underlying issues like fuel delivery or sensor malfunctions.

Anonymous 2017-03-31 10:02

Kev2: I forgot to mention that occasionally, the P0305 code appears alongside P0171. As far as I know, my vehicle is stock and has not undergone any modifications.

Anonymous 2017-03-31 11:13

It's worth checking the #5 fuel injector for proper pulsing, verifying fuel pressure, and performing the classic 'carb cleaner test' to detect vacuum leaks. A simple spray of carb cleaner near suspected hoses or connections can reveal if a leak is causing the lean condition—search online for 'carb cleaner to find vacuum leak' for detailed instructions.

Anonymous 2017-03-31 18:46

I'll be away for a few days, but when I return, I’ll try diagnosing this myself. If that doesn’t resolve the issue, I’ll follow up with more details or testing results.