I was recently asked to investigate an intermittent loss of power on a 2005 Peugeot 307 diesel accompanied by MIL illumination. This was a new customer so there was the potential that the vehicle had possibly been looked at elsewhere, it is not unusual for us to be asked to look at vehicles that have visited numerous garages first.
Upon driving the car into the workshop I noticed the engine malfunction light was illuminated and that there appeared to be a lack of boost pressure. A visual inspection in and around the engine bay confirmed my suspicions as I noticed numerous new parts had been recently installed. I began with a diagnostic check using our Peugeot Planet diagnostic tool which indicated numerous historical and two permanent error codes which were P2565 (turbo valve position copy signal) and P2563 (turbo valve position copy signal higher than setting).
This particular system utilises a turbocharger wastegate position sensor to monitor and relay VVT position, the PCM has a "specified" value for certain operating conditions and the sensor displays a copy or repeat value, any abnormalities here could set the two codes found. The sensor (mounted above the wastegate actuator) has three wires, I checked the voltages (component disconnected) which corresponded to manufacturers specified values.
Next I needed to carry out false actuation of the wastegate actuator to check both the sensor signal and the integrity of the internal diaphragm, this is achieved by operating the wastegate actuator (engine off/ignition on) using the Mityvac tool, with this I could simulate various actuator positions and monitor the relevant sensor signal. I could see from the oscilloscope display that the sensor signal was erratic and implausible, indicating a faulty sensor (see photo).
A new sensor was obtained and installed to the vehicle, a second check revealed appropriate sensor signal and boost pressure was restored.