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Hi All,

I've owned a 2004 Cayenne Turbo now for a year and its a great car when all is working correctly. In the time that I have owned this car, I have been unlucky enough to receive a few error codes on the durametrics program I have or lately on the Rev Diagonistic tool I have for my iphone.

I'd just finished fitting new parts for the fuel evap valve and a compressor rebuild kit, and re-setting all the codes in the ECU and all was fine, prior to going away, working abroad for 5 weeks, and all was good when I left.

I've got back to find the battery flat (no shock there) but after re-charging it for a day, and going for a good long drive in the country, the car is now majorly playing up, giving me 5 error codes. These are :

P0153 O2 sensor slow response (Bank 2, Sensor 1) - (Think this is fair enough, just wear and tear, getting old)

but tonight I have this lot :-

P0299 Turbocharger Underboost

P0300 Random / Multiple Cylinder Misfire Detected

P0306 Cylinder 6 Misfire Detected

P0305 Cylinder 5 Misfire Detected

Now could the above four codes be caused by a poor battery? I've put my multimeter across the battery and it's only about 12.5v sitting idle, although when the engine is on, it's getting the full 14v from the alternator.

I'm looking to go and get a new battery next week, but do I go and get it from my local porsche dealer?? or can I get one from the volkswagen dealer (normally the same part as a toureg, but cheaper) or do I go and get one from a parts store??

lastly, I was on the phone to my local dealer this morning and I was asking about coding or re-flashing the ECU, and thing led to another and we got onto the subject of the error codes, storing them and re-setting them.

They said to me "when fitting the likes of the oxygen sensor, or the evap valve, the part has to be coded into the ECU". Is this the same as re-settng the codes using the durametrics or Rev app that I have?

They also said that, some programs like the bosch systems can't reset the ECU properly and only the Porsche centre computers that the dealers use can reset the ECU properly & fully. Is this BS?, because this is the first I have heard of this?

Thanks in Advance



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New parts such as an EVAP valve do not have to be coded into the DME, that is complete BS. Are you sure there are no vacuum leaks from the work performed when the valve was replaced?

A weak battery can cause many odd issues so I would address that issues straight away. You can purchase the battery from anywhere so long as it's the correct group size.

Replace the battery, clear all codes and monitor any that return. Do not operate the vehicle of the check engine is flashing as it will damage emission components.

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To add to wvicary's comment..

The codes can be cleared with your Durametic tool.. so new battery, clear codes, see if any reappear, report back.

The misfire codes are typically seen when the coils are on their way out - but misfires could also be caused by low battery voltage (as can many other oddball codes.)

I'd avoid the dealer you're talking to - they're lying to you. Discrete component don't need registering.

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Cheers guys for you're feedback.

Right - update, changed out the battery and despite an error message on the display about a fault with he stability management, it disappeared when I rolled off the driveway. Took the car for a good run and the only one that has come back regular (other than P0299 underboost) is the oxygen sensor on bank 2 before the cat. This is to be changed out on Thursday.

As for the underboost, that's a whole bigger can of worms to investigate another day!

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