Turbo pressure sensor fault

[tessneil]

My 55 reg GT TDI went into limp mode on the motor way. Since turning it off and restarting all appears fine. I've had it into a garage and it was showing a fault with the turbo pressure sensor. They did Boost pressure test (does this not take long to do? as I didn't seem to be there very long) and said this was fine. They think it could need a repair of control unit plug on engine wiring loom but would need it in to check this and other posible causes. Unfortunatl,y wiring is not covered in my warranty so would like to be sure this is a common problem as the labour could be costly.

Any advice would be greatly recieved.

[Doctle Odd]

It's a little solenoid mounted to the bulkhead. 3 small pipes and a plug are attached to it. If you want to change it yourself

1 Skill level = 1/10
2 Time = 10 - 15 minutes.
3 Cost = Less that £50.00 from main dealer
4 Smugness after 10/10

You'd still need to get the fault code cleared with VCDS

Time to test the boost pressure can vary, lots of variables like was it checked using diagnostics like VCDS or the old way using pipes gauges etc. Boost wouldn't be down after the car was switched off and restarted

[tessneil]

It's a little solenoid mounted to the bulkhead. 3 small pipes and a plug are attached to it. If you want to change it yourself

1 Skill level = 1/10
2 Time = 10 - 15 minutes.
3 Cost = Less that £50.00 from main dealer
4 Smugness after 10/10

You'd still need to get the fault code cleared with VCDS

Time to test the boost pressure can vary, lots of variables like was it checked using diagnostics like VCDS or the old way using pipes gauges etc. Boost wouldn't be down after the car was switched off and restarted

Thanks for that. Just wondering why the garage didn't suggest just replacing the sensor??? I took it to a VAG specialist as they said they had most up to date diagnostics.

[zollaf]

do you happen to know the actual fault code that they came up with. the boost pressure sensor is mounted in the inlet pipework somewhere and tells the ecu what pressure is in the manifold via the turbo. the valve that doc is on about uses a vacuum to regulate this pressure via the ecu. it sends a vacuum to the turbo to adjust the variable nozzle. the normal fault is the turbo clogging up with soot and failing to move far enough to reduce the boost pressure and this is when an overboost fault is registered that will result in limp mode, as the ecu cuts the fuelling to save the engine from detonation to to overboosting. to test the boost you need to test drive the car whilst a passenger observes the live data looking specifically at the boost pressure and how the actual pressure compares to the desired pressure. this can't be done without driving unless you happen to have a rolling road in your workshop.
so, what you need to get is the actual fault code that was recorded. if we know this then we can advise, anything else is just speculation and won't help you.
edit, my guess is the garage didn't suggest replacing this sensor as they sound like they don't actually have a clue.

[Doctle Odd]

DOH! I defer again to your more logical thought processes Z!

do you happen to know the actual fault code that they came up with. the boost pressure sensor is mounted in the inlet pipework somewhere and tells the ecu what pressure is in the manifold via the turbo. the valve that doc is on about uses a vacuum to regulate this pressure via the ecu. it sends a vacuum to the turbo to adjust the variable nozzle. the normal fault is the turbo clogging up with soot and failing to move far enough to reduce the boost pressure and this is when an overboost fault is registered that will result in limp mode, as the ecu cuts the fuelling to save the engine from detonation to to overboosting. to test the boost you need to test drive the car whilst a passenger observes the live data looking specifically at the boost pressure and how the actual pressure compares to the desired pressure. this can't be done without driving unless you happen to have a rolling road in your workshop.
so, what you need to get is the actual fault code that was recorded. if we know this then we can advise, anything else is just speculation and won't help you.
edit, my guess is the garage didn't suggest replacing this sensor as they sound like they don't actually have a clue.

[tessneil]

Thanks Zollaf,

They didn't give me the code but I will ring up tomorrow and try and get it, they do say they are vw specialists (hmmm)Also that it would need a road test. My mechanical knowledge is sparce to say the least so pretty much have to believe what they say but having read a few threads from people will similar problems I've not noted anyone mention wiring loom. Had the car a month and has been my must have car for ages so praying it's not too many pennies to sort.

[tessneil]

Been onto them this morning, error code 16618. Says I'll need new turbo.....please tell me he's wrong :-(

[Sam]

16618/P0234/000564 - Ross-Tech Wiki

[zollaf]

so once the n75 valve and boost sensor have been ruled out, it looks like your turbo may be gummed up inside. now, you can replace the turbo as that would be the ultimate cure. you could also remove the turbo and give it a good clean. plenty of people have had great success in doing this. i even had a beetle in with the same fault and a good italian tune resulted in a massive cloud of black smoke followed by normal operation. that was over a year ago and no problem since. there are products that can be sprayed into the turbo to loosen the soot, such as mr muscle oven cleaner or innotec, but these seem to have limited results.
but first the root cause needs to be established with a test drive and observation of live data, followed by manually operating the boost controller on the turbo using a vacuum pump to observe the amount of movement. often working the turbo like this through its full range of movement is enough to get the vanes working properly again and the fault goes away, but only temporarily.

[Crasher]

The sensor is on the boost pipe and it is extremely unlikely to be faulty, it will be a clogged up turbo as Zolly says.