'57 plate 3.0 tdi - Boost Actuator issue - P0046


Registered User
so i bought myself a '57 plate 66k A6 Allroad

Drove it 200mile and got a limp mode - no lights on the dash

turned her off - back on again - everything OK

process repeated 30mins later, and the day after and so on for a week.

Then on a longer run to Scotland she didn't reset when turned off and I got an "Engine management" light come on. This stayed on for 2 days... then went out... but then came back 200 mile later. No flashing "Coil" lights.

A Draper ecu reader gadget came up with
Turbo Boost Control Solenoid Circuit Range / Performance.

Went to a garage (non-audi) and he confirmed the Boost Actuator was throwing an error.

We thought we had two options -
- Clean the turbo
- OR Replace the Turbo.

Said garage then spoke to an Audi dealer who suggested the following
- New Turbo
- AND New Exhaust Manifolds
- AND New EGR Bypass.

Audi price - £4500
Their reasoning is apparently that the manifold could be disentegrating and pieces of metal are therefore lodging in the turbo vanes.

I have searched for hours to find any problems / issues with Exhaust Manifolds. Found none.

I did find one post on one forum from a bloke with a similar sounding problem who got advice from Audi Warrington.

Has anyone heard of issues with exhaust manifolds?

I dont doubt there could be problems with sensors or tubes/pipes... but exhaust manifolds???

any pointers gratefully received


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Exhaust manifolds disintegrating, sounds a bit far fetched, but speculative diagnosis without visual inspections.


Well-Known Member
VCDS Map User
That disintegrating was a fault on the A4 B5/A6 C5 2.7 V6 Bi-turbo petrol engine, never heard of it affecting the 3.0 TDi/2.7TDi engines. Don't replace the manifolds it's BS.

Also if you going to bypass the EGR system, then you will need to have a remap that deletes the EGR from the ECU. Otherwise the engine management light will come on and it may go into limp mode again.
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Staff member
VCDS Map User
I suspect that engine has a BV50 turbo, These have issues when the VNT mechanism clogs up with the turbo actuator. It struggles to move the VNT through the full range and can even get damaged internally.
Cleaning the VNT may help but it's likely the actuator may need replacing .
These need to be set up you can't just bolt a new one on.
Have a google on BV50 turbo actuator. I think somebody had issues with one on here.