System Diagnosis - Fuel Metering System

Some failures of this system will result in an "Engine Cranks But Will Not Run" symptom. If this condition exists, refer to CHART A-3. Testing and Inspection

CHART A-3 will determine if the problem is caused by the ignition system, PCM, or fuel pump circuit. If it's determined to be a fuel problem, CHART A-7 should be used. This includes the fuel injectors, pressure regulator, fuel pump and fuel pump relay. The fuel system wiring schematic is covered in CHART A-5. If a malfunction occurs in the fuel metering system, it usually results in either a rich or lean HO2S signal. This condition causes the PCM to change the fuel calculation (injector pulse width) based on the HO2S reading. Changes made to the fuel calculation will be indicated by changes in the long term fuel trim values which can be monitored with a scan tool. Ideal fuel trim values are around 128; long term fuel trim values above 128 indicate that the PCM is adding fuel to compensate for a lean HO2S signal. Some variations in fuel trim values are normal because all engines are not exactly the same. If the evaporative emissions canister purge is "ON," block learn may be as low as 90. If the fuel trim values are greater than 138, see DTC P0131 (formerly DTC 44) for items which can cause a lean HO2S signal. Testing and Inspection