Diagnostic Trouble Code (DTC) Management

The engine control module (ECM) determines how much the engine is misfiring by counting the number of misfires during a certain number of engine revolutions. If the engine control module (ECM) detects a certain number of misfires during 1000 engine revolutions, this is interpreted as misfiring which affects emissions. If the misfires exceed a certain value during 200 engine revolutions, this is interpreted as misfiring which damages the three-way catalytic converter (TWC).

Diagnostic trouble codes (DTC) for misfiring will light the malfunction indicator lamp (MIL). If there is risk of damage to the three way catalytic converter, the malfunction indicator lamp (MIL) will flash during misfiring and then switch to a constant light.

The engine control module (ECM) registers and stores the engine speed and load parameters within which the misfire was detected. For the diagnostic trouble code (DTC) to be stored, the misfire must occur twice more within the same engine speed and load parameters.

In the event of emissions related misfiring, the malfunction indicator lamp (MIL) lights during the second operating cycle and a diagnostic trouble code (DTC) is stored.

If the misfire stops, the requirements for the engine speed and load parameters must be met without misfiring before the engine control module (ECM) will begin counting down to extinguish the warning lamp and erase stored diagnostic trouble codes (DTCs) for misfiring.