PFI System Check: Notes

WARNING: This page is about a different car, the 1990 Cadillac Fleetwood and 1990 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.

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 telltale, driveability problems, engine will not start or engine stalls after start.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) Lighting of Engine Control System Fault telltale during cranking confirms power and ground to ECM.

Test Number 2) If Engine Control System Fault light is on with engine running, check for ECM codes. Diagnose codes before proceeding with system check.

Test Number 3) After codes are corrected, ability of PFI system to control fuel delivery to engine must be checked.

Test Number 4) Check for proper closed/open loop operation.

Test Number 5) If closed loop is achieved, fuel system has to be checked for rich, lean or proper fuel control. The PFI system has ECM data parameter P.1.8 integrator. This monitors oxygen sensor rich/lean status and drives fuel system richer if oxygen sensor is lean, or leaner if sensor is rich.