Chart C1 - ECM Replacement Check

WARNING: This page is about a different car, the 1989 Cadillac Fleetwood and 1989 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.

Prior to replacing ECM, ensure that connector contact circuits are functional, and that there are no shorts from battery voltage to ground on any ECM circuits.

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

Clean all terminal contacts. Replace any coolant temperature sensor and connecting harness that has allowed water to seep into the conductors.
Test for shorts to relay, solenoid or ignition. Any circuit which has a resistance of less than 20 ohms is shorted. Diagnose and replace parts as necessary.
Check ISC circuit for shorts to ground or internal shorts. ISC resistance should be 4-100 ohms.

Fig 1: Chart C1 Schematic - ECM Replacement Check

Fig 2: Flow Chart C1 - ECM Replacement Check