CEL issue

[drewski1990]

CODE: P0171 - Bank 1 Lean

There has been a number of threads about this CEL already, but I haven't found one that discussed the possibility of the air filter. I have already changed both 02 sensors, but the light remains on. I was wondering if the air filter has anything to do with it because of more air flowing through the less restricted filter. I suspect the filter because the light turned off when I was at Napa CA, where weather is hot (less air). It turned back on the next day when I came back to San Francisco, weather is much cooler (more air).

Something contradictory about this issue is that when I first installed this filter (2 years ago with no CEL problem), the light came on and went away after half a day. So one of two problems, filter or MAF?

 

[YlwMSP]

The P0171 usually means a vacuum leak somewhere, check your lines

 

[drewski1990]

The P0171 usually means a vacuum leak somewhere, check your lines

ohh interesting. I will do that. I do get some hickups every so often when I am at idle.

 

[drewski1990]

Is there a way to check whether the MAF needs replacement? I dont have an AF gauge to monitor the ratios. Would I expect the engine to bog down when it hits boost if I do a quick test to disconnect the sensor? My smog test is soon, I need to fix the light asap. thankss

 

[YlwMSP]

It will die if you don't have the MAF connected, the ecu will have no idea how much air is entering the engine, thus not know how much fuel to inject.