The common rail engine management system has a triple software monitoring system in the IDM, which brings the engine to a standstill in the event of a critical software error in the system. This triple monitoring system works as follows:
โข Deletes all injection operations still present in the module,
โข Closes the fuel metering valve to prevent any further increase in fuel pressure in the fuel rail,
โข Brief, intermittent actuation of the fuel injectors to rapidly dissipate the fuel pressure.
In addition to the triple software monitoring system, a module hardware monitoring system has been integrated for monitoring the fault-free functioning of the individual components of the IDM.
If the system detects a module hardware error, current supply to the fuel injectors is interrupted.
After the engine has been switched off by the software or hardware monitoring system, it is generally possible to re-start the engine by switching the ignition OFF and then ON.
The system software continually monitors the following sensors/actuators to see that they are working properly:
โข Fuel pressure sensor,
โข CKP sensor,
โข CMP sensor,
โข Fuel metering valve.
If one of these sensors fails or malfunctions, the engine is stopped by the PCM.
In addition to sensor monitoring, the following situations may result in the engine being switched off:
โข Drop in pressure in the fuel rail because the fuel injector opening period was longer than calculated by the system (e.g. fuel injector sticking or dirty),
โข Fault is detected via the pull-in current of the fuel injectors.
The latter two situations do not require any additional sensors or actuators in the system.
All the input parameters (sensors) of the PCM are monitored for short circuits and open circuits.