I spent today in a Porsche service workshop, where the technicians had returned from a recent handling course at KW Suspension and were repairing an electrical fault on a Porsche 997 Carrera. There’s no keeping me away from watching Porsche repairs going on so I was happy to get the full story.

The car had a sidelight problem – there were no sidelights working on the 997. They stripped the front compartment and broke out the PIWIS tester, as used at official Porsche centres. This is one of few UK independent Porsche specialists licensed for the latest in-house Porsche technology.

PIWIS has a programme of system diagnostic tests in conjunction with a test probe, so the sidelight problem was soon traced to a bad wire (the grey one). When linking the connectors with a new wire solved the problem, all that remained was for Steve to splice in a new wire and run it back to the switch.

“Sometimes when a new wire is made, copper strands in the weave don’t mesh correctly and that incomplete joint eventually fails,” explained the mechanic. “Changing the complete wire is the most effective repair. Finding this break was relatively simple with the front stripped, PIWIS hooked up and a probe checking voltage at the front control module. As the name suggests, that box manages everything in the front part of the car: luggage lamp, cooling fans, lighting and so on.

“Solving this problem on the Porsche 997 was a doddle compared to PCM problems with a Porsche Cayenne a while back. That was eventually traced to ignition trouble, but it took two days to find it. The biggest problem with Cayenne is the modules are buried under other parts, and even taking out a seat takes hours. As with all wiring diagnosis, you eventually get there with a logical approach, good wiring diagrams and some help from PIWIS.”