Fuel Metering System Check

Some failures of the fuel metering system will result in an Engine Cranks But Will Not Run symptom. If this condition exists, refer to the Cranks But Will Not Run chart. See Diagnosis By Symptom. Symptom Related Diagnostic Procedures
This chart will determine if the problem is caused by the ignition system, the PCM, or the fuel pump electrical circuit.

Refer to Fuel System Electrical Test for the fuel system wiring schematic. Fuel System Electrical Test
If there is a fuel delivery problem, refer to Fuel System Diagnosis, which diagnoses the fuel injectors, the fuel pressure regulator, and the fuel pump. Fuel System Diagnosis
If a malfunction occurs in the fuel metering system, it usually results in either a rich H02S signal or a lean H02S signal. This condition is indicated by the H02S voltage, which causes the PCM to change the fuel calculation (fuel injector pulse width) based on the HO2S reading. Changes made to the fuel calculation will be indicated by a change in the long term fuel trim values which can be monitored with a scan tool. Ideal long term fuel trim values are around 0%; for a lean H02S signal, the PCM will add fuel, resulting in a fuel trim value above 0%. Some variations in fuel trim values are normal because all engines are not exactly the same. If the evaporative emission canister purge is ON, the fuel trim may be as low as -38%.

If the fuel trim values are greater than +23%, refer to DTC P0131, DTC P0151, DTC P0171, and DTC 1171 for items which can cause a lean H02S signal. Testing and Inspection