Detection Condition

• DTC P0171 indicates adaptive fuel control air/fuel ratio is too lean (right bank).
• DTC P0174 indicates adaptive fuel control air/fuel ratio is too lean (left bank).

Fuel control system uses fuel trim tables stored in PCM to compensate for variances in fuel system components from normal wear and aging. The fuel trim strategy learns deviations during closed-loop engine operation. Fuel trim has 2 means of adapting; a long term fuel trim and a short term fuel trim system. Inputs from ECT, IAT and MAF/IAT sensors are required to activate fuel trim adjustments. The HO2S detects presence of oxygen in exhaust and provides PCM with feedback identifying air/fuel ratio. A fuel trim factor is added to fuel injector pulse width calculation according to long and short term fuel trims. Long term fuel trim values at their rich or lean limits indicate a fuel system malfunction.