Hello! I have a problem with the CEL reading the code P0171.

It came on last Sunday while I was in downtown San Francisco, after I did a hard stop(since I realized there was a parking ticket on my windshield...). I cleared the code but the day after it came back on again. The car is running fine though so it has me wondering what exactly is causing the code.

Thank you in advance.

 

P0171 is a lean fuel condition. first check for any vacuum leaks in the system, PCV, brake booster etc...you SHOULD check fuel pressure as well. if all these checkout ok, then you may need to test the IAT sensor. out of adjustment valves can also cause this code to set.

 

Ok! I will check for leaks and cracks. Unfortunately I don't have the tool to check the fuel pressure.
Do the valves need adjustment at 80k miles? Just curious.

 

valves would be your last option if everything else checks out. usually adjustment for them occurs only when they become noisy. but if they've never been done and you have 80k on the clock it wouldn't hurt.

 

I was inspecting for leaks or cracks and noticed that something wasn't connected to the intake tube that connects to the air filter. Not sure what the piece is called but I plugged it back in and am gonna drive the car around and see if that was the problem and I will definitely check if the valves need adjustments.

 

Great, let us know what happens.

 

The P0171 can also just be the Mass Air Flow (MAF) sensor being dirty. Check the condition of the air filter and gasket. Then use some MAF sensor cleaner spray (CRC makes it) on the sensor.

 

See pic.

 

Only if he has a SULEV engine

 

He or she is in California. The California emission may be the SULEV.