Ignition Timing Control (Siemens)

The crankshaft and camshaft position sensors are used to determine precise timing of the ignition coils.

If the camshaft position sensor signal becomes impaired during engine operation, precise single ignition triggering continues.

If the signal is still impaired on the next engine start up, the system triggers the coils in double ignition to provide (failsafe) running.

Additionally, the secondary side of the ignition is monitored using the ignition feedback resistor.

The control module measures the duration of time it takes the monitored voltage drop for each ignition coil to dissipate below two volts. The time scale constantly changes based on engine speed.
- If there is no feedback signal present (0 volts) there is no spark present,
- If the 2 volt signal is not maintained long enough, the control module detects this as a week spark.

Primary and secondary monitoring is used in conjunction with the mechanical misfire detection feature introduced with the M5.x system. This combination assures maximum misfire detection and prevents possible engine damage and reduced emissions with the presence of a misfire.