Ignition Control

The M52 continues to use the stationary ignition system (RZV). Control of the ignition coils is an output function of the Siemens MS41.1 Control Module. The control and monitoring of the ignition system is similar to the Bosch DME M5.x system. This includes monitoring of both the primary and secondary functions of each ignition coil.

The RPM/reference and Camshaft position sensors are used to determine precise triggering of the ignition coils. If the Camshaft sensor is defective, the system can trigger the coils in double ignition to provide emergency (fail-safe) running.

The primary side of the ignition coils is monitored at the final stage in the MS41.1 module. If a fault occurs with one coil, the respective fuel injector will be shut down to prevent raw fuel from entering the catalyst. The fault will be stored in memory and depending on OBD II requirements, the Check Engine Lamp will illuminate.

The secondary side of the ignition is monitored using the ignition feedback resistor and the mechanical misfire detection feature introduced with the M5.x system. The control module monitors the voltage drop across the ground side of the secondary coil circuit if a ground pulse is missing, the respective fuel injector is shut down.

The control module also monitors the speed of the engine via the Crankshaft Position sensor.

Every time a cylinder fires, the thrust on the piston causes the speed of the crankshaft to increase. If the increase in speed is missing relative to when a cylinder fires, the control module sees this as a misfire. This will also cause the fuel injector for that cylinder to be shut down and a fault will be logged in the fault memory. If the criteria for OBD II is satisfied, the Check Engine Lamp will also illuminate.