TEST ECM GROUND CIRCUIT: Measure resistance between ECM and chassis ground using the backside of ECM harness connector as ECM side check point. Repair any problem found.

TEST ECM CONNECTOR: Disconnect the ECM connector and visually check the ground terminals on ECM side and harness side for bent pins or poor contact pressure. Repair any problem found.

If problem could not be found in Steps 1 and 2, the ECM could be faulty. If so, make sure there is no DTC before replacing the ECM with a new one, and then check the vehicle again. If DTC is found, examine this first before replacing ECM.

RE-TEST THE ORIGINAL ECM: Install the original ECM (may be broken) into a known-good vehicle and check the vehicle. If the problem recurs, replace the original ECM with a new one. If the problem does not recur, this is an intermittent problem. (Refer to "Intermittent Problem Inspection Procedure" in Basic Inspection Procedure.)