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Turbo Problems


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Hi There. Forum virgin here! but after some surfing, seemed like this was the place to post.

I've got a 2002 Passat TDI 130BHP Tiptronic.

Last week I took it into a new local garage for its 130k service, MOT and CV Joint replacement. The MOT required the headlight unit to be replaced as the adjuster was broken.

When I picked up my vehicle, there was something seriously wrong with its performance. Previous to taking it in, it was a nippy little beast, accelerating nicely when you put your foot down.

Now, I put my foot down and hardly anything happens! In fact it had trouble going up a very small incline the other day! I took it back to the garage and they retraced their steps of the service/MOT to make sure they'd not left any wires/connectors off.

They re-replaced the fuel filter and air mass meter and checked 'everything' - but the problem still remains.

They did a diagnostic on it and it came back with the code:-

17964 - P1556 - TC pressure - control limit not reached.

Now, bearing in mind there was nothing wrong with the performance before I took it in, has anyone here got a clue as to what the problem might be?

I've seen a few posts where the wiring loom needed to be replaced and I've got a feeling (even tho I can't profess to be a mechanic in any shape or form) that they might have disturbed this while doing the other work

Many thanks in advance.

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Possibly a vacuum line not connected, the one going to the turbo actuator or pressure converter (n75 valve).

The fault code relates to lack of boost pressure from the turbo (basically the turbo ain't working). So, the N75 valve controls the turbo actuator mechanism to make it produce boost. The vacuum system provides vacuum to the N75 and this is what it uses to control the turbo. So if the turbo ain't producing boost the problem lies in

1. Turbo actuator stuck.

2. N75 not making actuator work.

3. Vacuum not present at N75 for it to switch to the turbo.

4. Turbo is working but boost hose has come off (loads of black smoke from the exhaust).


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The timing belt was replaced at 120k.

Beacuse the car was working fine before I took it in, I still feel its something they've disturbed while doing the service/mot/headlamp unit replacement.

Do any of the things you mentioned above need to be touched accessed to do the jobs that they did?

Thanks in advance smile.gif

PS That boost hose split about a year ago and was replaced.

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  • 3 years later...

Had similar problems with my car. Went to one garage in Southampton, who shall remain nameless, and they changed almost everything without curing the problem.

Took it to somewhere else - FANTASTIC!!! They had dealt with this issue many times before and the problem was resolved in no time.

MODERATOR EDIT: I know I'm a new user and I've definitely read the forum rules, so I certainly won't be posting any details of garages that might be deemed as SPAM advertising.

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