Turbo question

smog c6

Registered User
hi the turbo on my 2.7 tdi 2005 a6 has died. I’ve bought a new gtb1756 for it but this is the wrong turbo, there appears to be a bv50 with the VDO actuator on it. I thought all 2.7 tdi’s have the gtb1756 turbo with hella actuator. Is this correct?


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smog c6

Registered User
So I have now replaced the Turbo, however new faults have cropped up.

The reconditioned turbo is p/n 059 145 715E

The car drives really well and it feels like theres more power and its smoother, than with the previous turbo before it became faulty.

I am however getting Fault codes below, and I tested the car with a good run and discovered the car goes into limp mode (flashing glow plug light and low/no boost) around 3700 revs or more, this doesnt occur before that.

P3348 - Control Circuit for Controller for Turbocharger 1 (J724): Electrical Malfunction
P0234 - Boost Pressure Regulation, Limit Exceeded (Overboost Condition)

OBD2 - confirmed:
P0046 - Turbocharger/Supercharger Boost Control "A" Circuit Range/Performance

OBD2 - pending:
P0234 - Turbocharger/Supercharger "A" Overboost Condition
P0046 - Turbocharger/Supercharger Boost Control "A" Circuit Range/Performance

Any ideas what this may be? I feel like the VDO actuator needs to be calibrated.

smog c6

Registered User
Just following up, I have noticed when unplugging the connector to the turbo and replugging it the actuator stutters at the top position when going through its movemement. I have read online it is possible to adjust the turbo via loosening the 3 10mm bolts holding the actuator to the bracket and allowing the actuator to set its position and then tightening.

Could anyone with more experience exlpain how to do this, as I understand currently once the bolts are loosened someone should cycle the ignition from off to on, this would allow the actuator to test its motion. If it was physically outside the limits of its motion the actuator could now adjust as the bracket is now loose once position which allows the actuator to move through its full range of motion is found bolts should be tightened.

This method only works if the refurbed turbo has the same range value as the old one, eg if old one was say 19-79% and this refurbed one was 23-83% it would work as the range is 80%.

Am I understanding this correct?

smog c6

Registered User
I have had the turbo inspected by the company I bought it off. They replaced the actuator and calibrated the new one again, I recall a number 82% on the final cycle after this was done. He said the turbo was getting stuck on the top position. However this has not fixed the problem. The garage that replaced the turbo (different garage) are dumbfounded and said they cant do anymore.

The best way I can decribe my problem is the turbo doesnt always work when I floor it, like its not spooling up. however if I let go of the accelerator pedal and floor it again sometimes it does work. When it does work it is working from 1500rpm-3000... and higher and it does feel like its at full power. On the motorway I can tell the turbo works from 1500rpm onwards in 6th.

I have a new fault now Lambda sensor bank 1 sensor 1 open. I didnt realise diesels had o2 sensors. I have explained everything to another garage who said its worth a try changing it but may not solve the turbo problem. Does anybody know if a lambda sensor can cause this?

The original turbo had blown up, the exducer fan was damadged and a VGT vane had come off. Im wondering if these part flew down the downpipe and damadged the lambda sensor. Wonder why the lambda sensor fault hadnt shown before.


Registered User
The extra power and then limp mode sound linked. Unless your car is remapped it’s likely that it’s giving more power than standard and the system thinks it is over boosting and cutting power or going into limp mode. Because it cannot control/limit the power within its normal parameters it sticks it into limp mode thinking there is an over boost problem.

Fitting the wrong turbo(I’m assuming you’ve fitted a larger/more powerful one?) can cause head scratching problems.

I don’t know if it will or would work but it might be possible to remap the engine to allow the full use of the new turbo and have the correct fuel settings to suit it. This would in theory then tell the ECU that the extra boost is correct.

Does that make sense?


Audi A6 C6 2.0tdi 2011 Sline Special Edition
Could also be a gummed up turbo? Was it reconditioned and cleaned or just pulled of a scrap car and stuck In to yours? If you move the actuator is it completely free for its full range of travel?

smog c6

Registered User

Its fixed now, the problem was due to sticking turbo vanes, it was sticking in the open position, and somtimes in the closed position.

The turbo I bought was a reconditioned unit, It should have been fully refurbed including cleaning, new cartridge, balanced, calibrated and flow tested.

After all the issues I've been having I decided a fresh set of eyes were needed so I took the car to another specialist who diagnosed the issue. They replaced the turbo for thier own reconditioned unit and thankfully the turbo works perfect now.

I cant imagine how a reconditioned unit would have its vanes stuck within a day of driving, I honestly believe Ive been fobbed off by the first turbo specialist, he musnt have cleaned the vanes out. I cant understand people like them, I paid for a service, a good price, left the car with them for a total combined period of 6 weeks. I explained I would consider paying extra for diagnosing time yet they still fobbed me off.

The second specialist diagnosed it within 6 hours and had the job done within 2 days, and I paid £200 less.