A6 2.0 Diesel 55K in Limp with Boost Sensor error

[EminenceGrise]

I'm new here. I have an A6 Ultra 2.0 Diesel 2015 with 55K miles. Ii is used 70% of time on empty dual c'way road runs for 35 mile roundtrip 4x per week. Rest is 10% low-density light city traffic and 20% long M-way journeys. So, it is lightly loaded but with up-to-temperature usage virtually all of the time. In lockdown for 2 months and car barely used. First return to normal usage and A) front spring broke immediately ( very careful with speed bumps and no heavy usage !! ) and B) car suddenly went into limp mode ( I think ) mid-journey with flashing glow-plug warning but no MIL. Limped a return from this usual roundtrip and at end MIL came on with prior glow-plug warning. I have access to VCDS and here is error...

11901 - Manifold Pressure / Boost Sensor (G31)
P0236 00 [175] - Implausible Signal
MIL ON - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 2
Mileage: 90346 km
Date: 2020.05.29
Time: 13:02:31
Engine speed: 0.00 /min
Normed load value: 0.0 %
Vehicle speed: 0 km/h
Coolant temperature: 43 °C
Intake air temperature: 43 °C
Ambient air pressure: 1020 mbar
Voltage terminal 30: 12.240 V
Unlearning counter according OBD: 40
Charge air cooler inlet: pressure sensor 1 bank 1: raw value: 1345.4 hPa
Engine status: COENG_STANDBY
Engine status-Test_Program_Co Eng st COMPU VERB UBYTE: 0

I wanted to remove and clean the turbo boost sensor as a first step. However, I did not know where this was located. I reckoned eventually that it is above turbo to left of block. It had what looked like a 'standard' shape of boost sensor but that was on top of and integrated with a round plastic item with a 'metal straw' heading down towards turbo. This is secured by 2 x T30s. Can anyone confirm that this is the boost sensor and if not; where is it? Secondly, how is it removed - there are the obvious T30s mentioned but also some pipework across its location that looks as if it might interfere with removal.

I can guess that there can be many problems related to anything 'turbo' and so further thoughts/experience would be very welcome. Pls refer me to any previous work on forum to avoid your valuable time.

[Crasher]

I would be more inclined to think the turbo actuator is a bit sticky so the sensor is seeing a signal which it should not.

[EminenceGrise]

Crasher. Many thanks for your thoughts. Any advice on how to further diagnose or exercise/remediate actuator/vanes?

[Crasher]

I would have the turbo rebuilt and set up on a flow rig.

[EminenceGrise]

Crasher. Thanks again. I located boost sensor ( on bracket near scuttle at centre/right with part # 04L 145 049 F )and fiddled with it to see if wiring was faulty. I erased DTCs on VCDS and set off for a test trip to gauge whether turbo was sticky or otherwise obviously unserviceable. Car did not throw any errors immediately and performed as normal; it revved up and down range and changed gear on auto/manual. My conclusion from this is that the turbo mechanically must be A-Ok. Obvious candidate was boost sensor. However, on start this morning the glowplug error reappeared and the car again ran in LIMP mode. Before return journey I cleared the DTCs and left VCDS connected ( I am a tyro with it BTW ). The car performed exactly as normal for 15 - 20 miles. I ran the Autoscan again and noted two new errors; one not confirmed for a pressure reading on #3 cylinder and another for a MAF error. The MIL and glowplug were showing on re-start. Cannot get Audi service or spares to respond ( furlough ) so may test MAP for electrical response if I can apply pressure to it. Now getting a little confused and will repeat testing tomorrow.

[Crasher]

Can you post a copy of the code read using the hashtag code function shown in advanced reply.