The engine control module, or ECM, serves as the “brains” of the average automobile. The ECM controls several aspects of the engine, including the fuel and air mixture, valve timing and ignition spark control. The ECM also stores a number of codes collected by various sensors in the on-board diagnostic system, or OBD, during the operation of the vehicle. You can read the trouble codes generated by the “Check Engine” light to track down and fix performance and emissions issues.
Park the vehicle on a level surface. Turn the ignition switch to the “On” position.
Locate the OBD connector under the driver’s side of the dashboard. Unfold a paper clip and insert both ends into terminals “A” and “B” on the top right side of the connector. This location may vary depending on the type of OBD connector used in your vehicle.
Monitor the “Check Engine” light on the vehicle’s instrument panel. The light will flash once and briefly pause, then flash twice and pause, and continue the sequence three times. This is how the ECM displays a “code 12,” indicating that the vehicle is in diagnostic mode.
Monitor the “Check Engine” light for other diagnostic codes stored in the ECM. Consult your vehicle’s service manual for a list of codes used by that particular vehicle’s ECM.
