Malfunction Indicator Lamp (MEL)

The malfunction indicator lamp looks the same as the MEL you may be already familiar with (Service Engine Soon or Check Engine). The OBD II regulations require that the MEL illuminate according to a strict set of guidelines. Under OBD the MEL is turned on when the PCM detects a malfunction that will affect the vehicle emissions.

The MEL is controlled by the PCM. The MEL will be illuminated if an emissions-related diagnostic test indicates a malfunction has occurred. The MEL will stay illuminated until the system or the component passes the same test for 3 consecutive trips.

A vehicle that is experiencing a misfire malfunction that may cause damage to the 3-way Catalytic Converter (TWC) will flash the MEL once per second. The MEL will continue to flash once per second until the vehicle is outside of the speed and the load conditions that may cause damage to the TWC catalyst. The MEL will stop flashing and remain on steady once the vehicle is outside of the speed and the load conditions that may cause damage to the TWC catalyst.