NOTE: After the EGR valve is replaced or after the PCM is replaced/reprogrammed, the EGR valve must be initialized using the PCM (refer to the instructions in the current Service Literature).
Various versions are equipped with an electric EGR valve.
The EGR rate can be metered out more accurately by the electric EGR control.
Function
The electric EGR valve comprises the following components:
• Servo motor,
• Position sensor,
• the EGR valve itself.
The servo motor is a DC motor which is driven via PWM by the PCM.
The position sensor is a sliding contact sensor which supplies the PCM with an analogue voltage signal via the position of the EGR valve.
Effects of faults
Malfunctions at the electric EGR valve result in the EGR system being deactivated.
If the EGR valve jams open, the following symptoms may occur:
• increased black smoke formation,
• irregular idling,
• engine judder,
• reduced engine power output.
Diagnosis
The monitoring system:
• checks the servo motor as well as the position sensor for short circuit to ground/battery and open control loop.
• checks the measured values of the position sensor for plausibility.
• checks the EGR valve for unobstructed movement.
• detects a seized EGR valve.
The PCM performs a cleaning cycle after the engine is stopped. For this purpose, the EGR valve is fully open and closed a few times.
