PFI System Check
The PFI system check is an organized approach for identifying a problem caused by PFI system. Driver comments normally fall into one of the following: steady "ENGINE CONTROL SYSTEM FAULT" light, driveability problems, engine will not start, or engine stalls after start.
- Lighting of "ENGINE CONTROL SYSTEM FAULT" light during cranking confirms battery and ignition voltage to ECM.
- If Engine Control System light is on with engine running, check for ECM codes. Diagnose codes before proceeding with system check.
- After codes are corrected, ability of PFI system to control fuel delivery to engine must be checked.
- Checks for proper closed/open loop operation.
- If closed loop is achieved, fuel system has to be checked for rich, lean or proper fuel control. The PFI system has the ECM data ED36 and ED37 integrator. This monitors oxygen sensor rich/lean status and drives fuel system richer if oxygen sensor is lean, or drives fuel system leaner if sensor is rich.
- See SELF DIAGNOSTICS SYSTEM CHECK .
The integrator has a range of 51-204 counts. The integrator value will be 128 when ECM does not have to modify fuel rate to engine. The integrator will reset to 128, if fuel system is in acceleration, power enrichment, some deceleration or open loop modes. The integrator resets to 128 when oxygen sensor is not in control of fuel.
If integrator sees an oxygen sensor that is lean most of the time, the integrator value will go higher to try to add more fuel to engine. If integrator sees an oxygen sensor that is rich most the time, integrator value will go lower to try to drive fuel system leaner.
In this test, operate engine at closed loop (1000-2000 RPM with steady throttle) to stabilize integrator reading of 88-160. In most cases, this will indicate that fuel delivery system is okay.