Notice: Turn the ignition OFF when installing or removing the ECM connectors and disconnecting or reconnecting the power to the ECM (battery cable, ECM pigtail, ECM fuse, jumper cables, etc.) in order to prevent internal ECM damage.

When the ECM sets a diagnostic trouble code (DTC), the malfunction indicator lamp (MIL) lamp will be turned ON only for type A, B, and CNL, but a DTC will be stored in the ECM's memory for all types of DTC. If the problem is intermittent, the MIL will go out after 10 seconds if the fault is no longer present. The DTC will stay in the ECM's memory until cleared by scan tool. Removing battery voltage for 10 seconds will clear some stored DTCs.

DTCs should be cleared after repairs have been completed. Some diagnostic tables will tell you to clear the codes before using the chart. This allows the ECM to set the DTC while going through the chart, which will help to find the cause of the problem more quickly.