Take it step by step

Matt Cleevely, of Cleevely Motors in Cheltenham, investigates a cutting-out fault on a VW Passat Estate 2006

Published:  21 January, 2014

By Matt Cleevely

A 2006 VW Passat 2.0L PD TDi was brought to us via a breakdown service as an un-driveable car. The important first step along the repair route was to question the customer about the nature of the fault and find out how long it had been happening. After all, the customer knows their vehicle better than anyone else. Under what conditions had they noticed the fault? Had there been any other noises or strange behaviour?

The next job was to check the fault codes. A scan revealed the code for the crankshaft sensor circuit, which was not unexpected but why was the fault occurring only when under load? I chose to check live data via the scan tool and while doing so, I noticed the crankshaft sensor signal would fade and disappear when the fault occurred. Next, was to check if the signal was failing to be sent or if the ECU was not seeing it. On checking my data provider, I found that no wiring diagrams or pin data were available to me. This always makes life harder and my only option would be to find out the long-way-round.

Removing the airbox, intercooler hose and air-ducting on the nearside meant I could trace the loom in front of the gearbox. Sandwiched between the intercooler hosing and lower coolant hose to the radiator, I found the wiring loom chaffed (above) and only one wire was worn through - the crankshaft sensor signal wire! After cutting-out any corroded areas and soldering-in a new section of correct wire, the repair was complete. Much to the satisfaction of a very grateful customer.

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