The system on this engine incorporates 2 processes: A self-checking cleaning mechanism which operates each time the ignition is switched on and an 'Antisticking' feature.
The system performs of one or several successive opening and closing cycles. When complete, the engine ECU commands it to try and reach the maximum opening position. If it detects a block, it repeats the cleaning cycle. If it fails a second time to reach the maximum open position, then a fault is flagged up.
The system attempts to detect any 'sticking' of the valve by:
- Speed of movement of the gate of the electric EGR valve
- Errors in regulation of the position of the electric EGR valve
If the valve is stuck or is beginning to stick, a control signal is sent that vibrates the gate of the EGR to prevent the sticking. The amplitude of the vibration is determined by the degree of sticking. This process is only in operation when the EGR is in operation.
Of course, the above strategies are to prevent the valve itself from sticking and cannot account for any clogging further down the system for example, but I thought it worth a mention as at least you would know that the valve itself is working or not from any faults logged if there was an issue with the EGR valve sticking itself.