Shall I change the Oxygen sensor?

[belfry]

Cayenne 4.5 S 2003 122,000 miles


I haven't used the Cayenne for 10 days and when I tried to start it yesterday there was an odd noise when trying to start it. The AA came out and said that the engine was flooded. After a while they got it restarted and I used the car without problem for a couple of hours. I have not had this problem before and this is the first time in 3 years that the car hasn't started.

Today the CEL light is on and the engine feels lumpy. I have just had the AA back and 2 fault coded have come up
P0159+ O2 sensor circuit slow response (Bank 2 sensor2)
P0306 Cylinder 6 misfire detected

The AA suggest recovery to OPC.

Any suggestions?
Shall I change the sensor myself?
How easy is this (I have an old fashioned pit for access underneath)
Or shall I just let the OPC do the work? My only issue with this is that the neared OPC is 90 minutes away and I know I will end up having to get a train/taxi to go and collect the car.

[Pugley]

At face value I would say yes change it................

But second thoughts suggest that there may be an over fueling fault that is causing the O2 sensor to fail, rather than the sensor causing the fueling fault???

Unfortunately, I think you are going to have to cough up for the correct diagnostics if you cant sort it out yourself

[belfry]

That's the sort of sensible advice that makes PH so helpful. I went straight to the cheapest, simplest solution. Although, if it's a simple fix I might still try replacing the O2 sensor and seeing what result that has. Has anyone on here replaced the sensor themselves? And was it easy to do?

[Magic919]

I'd be looking into this more closely, as sensor 2 is post-cat on many cars and has little or no involvement with fuelling.

Changing a lambda is as simple as a spark plug swap, with one caveat; getting the old one out can prove tricky. Soaking it with penetrating oil for 24 hours, maybe applying heat, plenty of options.

Could well be two unrelated faults here. Perhaps a coil pack on the way out?

[D900SP]

If the engine is misfiring it will set an 02 sensor fault as the measurements the sensor is processing will be out of the tolerance parameters.

Fix the misfire first, which could be a number of things, and then run the system on a tester and see if the O2 sensor is actually working correctly.

For an '03 955, have the coils been updated?

O2 sensor aging is not necessarily a fault.

Edited by D900SP on Sunday 4th November 16:31

[belfry]

D900SP said:

For an '03 955, have the coils been updated?

Not in my ownership from 93k to 122k.

I know that the coils packs should be an area to focus on closely. Would failing coils packs lead to a flooded engine? Or an O2 sensor fault code?

[bobsan]

belfry said:

Not in my ownership from 93k to 122k.

I know that the coils packs should be an area to focus on closely. Would failing coils packs lead to a flooded engine? Or an O2 sensor fault code?

Yes and Yes

[asman0161]

hi
From past experience it looks as though coil number 6 is faulty which needs replacing. which is giving you the problems and the o2 sensor fault code has popped up on the diagnostic because the 02 sensor is sensing unburnt fuel through the exhaust.
once coil6 has been replaced and the engine running smoothly again the o2 sensor fault code will just need clearing.

hope this helps

[stup]

Coils is where I would start, more a common failure on this vehicle