Misfire Enabling and Malfunction Criteria

All of the following conditions must be met in order for the misfire diagnostic routine to be carried out.

^ Motor running
^ Ionization circuit synchronization has taken place (TRIONIC)
^ No deceleration fuel shut-off taking place
^ Vehicle vertical acceleration (VVA) sensor inactive (4 cyl MOTRONIC)
^ No significant variations in ABS wheel speed input (6 cyl MOTRONIC)

Hardware Required
The TRIONIC engine management system requires no new hardware to accomplish misfire detection as it utilizes the existing ionization function.

The MOTRONIC misfire diagnostic makes use of a revised version of the existing inductive crankshaft position sensor and the Hall-effect camshaft position sensor. The only totally new piece of hardware is the Vehicle Vertical Acceleration Sensor on 4 cylinder cars.

Concerns
The misfire DTC may be triggered by conditions beyond our control such as bad fuel, running out of fuel, erratic driving habits, etc. To meet the legal requirements, the diagnostic must be designed in such a way that it may take days or even months between the time that knock was first detected and the point at which the MIL was finally illuminated. As you may recall, it takes two failures to turn on the light in a case of emissions-related misfire.