Q: How do I know that my OBD system is working right?

The OBD system on your vehicle is a self-monitoring system. The Powertrain Control Module monitors and controls all of the systems and functions that regulate fuel, ignition, emissions, and engine cooling as well as having some minor control over air conditioning, traction control, and others. The way that the driver is informed of any malfunctions in the OBD system is through the Malfunction Indicator Lamp (MIL) or Check Engine light.

To verify that your OBD system is working normally, put your key in the ignition and start the engine. Watch the instrument panel for the Check Engine light. When you start the engine, the MIL should illuminate for several seconds. This occurs to verify that the PCM is checking all of its systems, components, and circuits for proper operation. After several seconds have elapsed, the MIL should go out. This verifies that the OBD system on your vehicle is working normally.

If the MIL does not illuminate, or comes on and stays on, then you need to have a trained technician like those at YourMechanic take a look at your vehicle. Checking the status of your Check Engine light could be as simple as a burned out bulb to something more involved such as an issue with the computer itself.