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Hi everyone, I have a 2010 gmc terrain 2.4L that has a p0171 - lean exhaust code, also occasionally accompanied by a tps position not plausible code (I can’t remember the code number - p2something) fuel trims are around 29-31% at idle in park and slightly improve when rpm’s increase to 3,000. Originally this car had a really horrible lean condition caused by the mass air flow sensor, reading around 15gm/sec at idle and fuel trims were maxed lean. Replaced MAF and it now reads correctly at around 2.8-3 gm/sec but I still have elevated fuel trims. Acts like a vacuum leak but I have smoke checked the intake manifold 2 times and found no leaks, plugged off the purge valve to make sure it’s not an issue, plugged off the brake booster as well. O2 sensor pegs rich if I drive it full throttle, and fuel pressure looks good on the scanner. Really seems to be a vacuum leak but I can’t find one, any ideas? Thanks
You say the trims only slightly improve at 3000 rpm?
What are you seeing for trims at that rpm? If they don't change much, then it may not be a vacuum leak.
Any work done recently? Thinking maybe wrong injectors, possibly the replacement MAF low quality causing problems?
Any flex fuel or incorrect flex fuel value learned in PCM?
Fuel trims are positive around 30-32% at idle and improve to around 24-26% at 3000rpm. I’m nearly 100% sure at this point it’s not a vacuum leak causing my issue, I changed the replacement mass air flow sensor with an oem known good sensor from another customer car with the same engine, no change. Fuel alcohol value reads 0% which I thought seemed strange but the other customer car read 0% as well
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