P0171 & 0174 codes

[jpruessner]

My SES light came on yesterday. Went to checker and got it scanned and found it is the P0171 & 0174 codes. The system is too lean. The guy at checker said it could be the O2 sensors. But I have done some reading and it may not be this. Anyone else have any ideas on this? Those O2 sensors are a bit pricy for all 4.

[GMMerlin]

Originally Posted by jpruessner

My SES light came on yesterday. Went to checker and got it scanned and found it is the P0171 & 0174 codes. The system is too lean. The guy at checker said it could be the O2 sensors. But I have done some reading and it may not be this. Anyone else have any ideas on this? Those O2 sensors are a bit pricy for all 4.

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor (O2S) input. During Closed Loop, the O2S inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the O2S indicate a lean condition, fuel trim values will be above 0 percent. If the O2S indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, DTC P0171 or P0174 sets.

The system will go lean if an injector is not suppling enough fuel.

A lean condition could be present during high fuel demand.

Inspect for any missing, loose, or leaking exhaust components forward of the HO2S.
Inspect for vacuum leaks at the intake manifold, throttle body, and injector O-rings.
Inspect the air induction system and the air intake ducts for leaks.
Inspect the secondary air injection (AIR) system for leaks, improper air delivery, and for the shut-off valves not closing.
Inspect the crankcase ventilation system for leaks.

You can replace the O2 sensors...won't fix your problem