Misfiring below an engine speed of 3000 rpm is detected by the misfiring detection system. Above 3000 rpm misfiring is detected by the ignition circuit monitoring (self-diagnosis) and prevents damage to catalytic converters.
The secondary circuit monitoring facility operated with a special resistor in the secondary measurement line, also known as a “shunt”.
If, after successful ignition, the threshold voltage for misfiring detection is not reached, a defect code is stored, the fault lamp activated (US models only) and the corresponding row of cylinders deactivated.