My much-loved 2004 Porsche Cayenne S (4.5 V8) behaved itself for most of this winter just gone, apart from a couple of minor hiccups. The first required a battery change, but the other was a little more challenging.

I should have seen it coming when the Cayenne would very occasionally take a few of seconds of cranking to get started when hot. I assumed it was some sort of fuel boil-off to do with the LPG system, but then it was a random occurrence and perhaps also happened when running on petrol.

Porsche Cayenne Poor Running

A few weeks ago, I filled up with LPG and was just driving away when I was forced to do an emergency stop. The hard braking caused the Cayenne to cut out and it was a bit of a pig to get started again. Eventually it did start, but would not pull away from junctions cleanly once I got it going. I thought it might be something to do with the emergency braking system (an Audi I once drove had something like this) so I pulled over, reset the systems and drove off, apparently cured.

The next day, the problem was back, with poor acceleration on the school run. I emailed Chris at JZM and asked what he thought. There were a few suggestions, but he could stick it on their Porsche PIWIS the following day to be sure. Next morning, I dropped the kids to school and headed for Kings Langley, where we plugged it in and read the fault codes.

There were a few things on there (as usual for any Cayenne), but one I had been looking for: crankshaft position sensor fault. The ECU said it had last happened at 41k miles, but first happened at 63k miles even though the car was now on 157k miles. I couldn’t see anything else. Mike had a good look through everything – bit of a pain as the Cayenne takes ages to give up its codes and the PIWIS diagnostic walk-throughs only work on post-2006 cars –  before deciding to do a master reset, run it again, then read the codes and see what was showing.

Cayenne Crankshaft Position Sensor Failure

Having done the reset, the Cayenne wouldn’t start. It would crank and crank but no start. Complete failure in the best possible place: a decent independent Porsche workshop! We left it a while and then like magic it started fine. As the last major fault code had been for crankshaft position sensor, we agreed this was the first thing to change. I borrowed a courtesy car and Mike changed the sensor the following day, which seemed to cure the problem.

Thoughts since the change? Wow, what a difference. Things the Cayenne used to do which mildly annoyed me have all disappeared. It starts first time, every time, and pulls cleanly from anywhere in the rev range: easily the smoothest it has been in my 40k miles of ownership. Still needs flicking down a gear when you really want to get moving, but a huge improvement overall.

If you’ve got a 955 Cayenne with 100k miles or more and it’s on the original CPS, get it changed and bring your Cayenne back to full health, before it leaves you stranded. Will be a bit of a nightmare job, as the plug is in quite a tight spot behind the top of the engine, but “it’s not that bad” according to Mike. One tip on where to get the part: as official Bosch agents, JZM bought my crank position sensor straight from Bosch and saved me quite a few quid. Good work!

PS: I collected the Cayenne and brought it home. That night, this happened (above). I was not pleased! Three other cars around it were also keyed so it wasn’t an anti-Porsche thing. My Polo was parked in front of it and that was not keyed, so it wasn’t an anti-me thing either. Such is life.

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