Maxima 2001 fault code P0171 P0174



I have fault codes P0171 and P0174 (system too lean)the only performance behavior to indicate a problem is when the engine is cold it hesitates initially. Doesn’t this engine behavior narrow the possible problem and what is it?

Thank you



Having the two codes indicates that this is a V6 engine, and that both sides of the engine are running lean (too little fuel, or too much air).
When the engine is cold, how does it hesitate? During initial acceleration? When the gear shift is placed into Drive? When?
Measure the fuel pressure. The fuel filter is inside the gas tank; so, you can’t change it.
Check the large, black, plastic air intake tube after the air cleaner. Make sure that it’s tightly connected at both ends, and that any hoses are well connected to it.


One condition that can set these codes is a dirty Mass Air Flow sensor. If the sensor is dirty enough where it’s unable to measure the actual amount of air entering the engine, the O2 sensor(s) will measure more air in the exhaust stream than the amount of air measured by the MAF sensor. This then results in a lean condition in both banks.

The simplest thing to try is purchase an aerosol can of MAF Sensor Cleaner and give the MAF sensor a good cleaning. Reinstall it and see if the Check Engine light turns off.