Reductant Pressure Sensor Circuit Fault [Resolved]

[JimmyAK]

Showing some impeccable timing just before the Christmas break, my engine warning light has come on. Did a VCDS scan and it's showing fault with the Reductant Pressure Sensor Circuit.

25145 - Reductant Pressure Sensor Circuit
P204B 00 [039] - Implausible Signal

There's no other messages on the instrument cluster and the van seems to drive normally. I tried clearing the fault but it soon returned. Am I right that this is something to do with the AdBlue system? More importantly, with little chance of getting it into a dealer before Christmas, does anyone know if it will it do any damage to continue to drive it with this fault?

 

[mmi]

Please post a complete engine section fault report - besides exact engine type in there should be also a freeze frame data about conditions triggering the fault.

 

[JimmyAK]

Address 01: Engine (J623-DNAA) Labels: None
Part No SW: 05L 906 023 D HW: 05L 907 309 F
Component: R4 2.0l TDI H80 1164
Revision: N1H80--- CVN: 9ED8FB07991E9EBCA3C795CF64CF85E9A3C795CF43FB2DAA
Coding: 002500340324050800000000000000000000000000000000
Shop #: WSC 00035 377 00124
ASAM Dataset: EV_ECM20TDI01105L906023D 006006
ROD: EV_ECM20TDI011_VN46.rod
VCID: 290FF246A9712CB39CC-807C
VINID: 9E606AAAA1D8A9EA00048008205635C5E5
1 Fault Found:
25145 - Reductant Pressure Sensor Circuit
P204B 00 [039] - Implausible Signal
[Reductant Pressure Sensor Circuit Range/Performance]
Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Reset counter: 40
Mileage: 8974 km
Date: 2022.12.21
Time: 10:22:05
Engine RPM: 968.50 /min
Normed load value: 31.4 %
Vehicle speed: 0 km/h
Coolant temperature: 7 °C
Intake air temperature: 6 °C
Ambient air pressure: 990 mbar
Voltage terminal 30: 13.000 V
Unlearning counter according OBD: 40
Outside temperature sensor 1: B1: raw value: 5.5 °C
Pressure sensor for reducing agent: measured pressure: 9993 hPa
Reducing agent pump module relative press.: calculated: 0 hPa
Sensor for reducing agent tank temperature: temperature: 6.6 °C
Reducing agent flow pump: time between strokes: 0 ms
Reducing agent system: current status: Idle
Reducing agent system: current status-Test_Program_SCR Con State 01 UBYTE: 10
Readiness: 0 0 0 1 1
-------------------------------------------------------------------------------

 

[mmi]

Thanks,
Engine DNAA is one of the new engines introduced on T6.1 - it has a revised NOx reduction system (AdBlue) thus no experience about it yet.

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www.volkswagen-newsroom.com

Anyways,

Pressure sensor for reducing agent: measured pressure: 9993 hPa

I believe the above is what has triggered the fault. I have a 4-hour recording from @Pauly from his engine (exactly the same DNAA) and it seems that the maximum pressure during his journey was only 6500 hPa (6.5 bar).
Anyways, impossible to conclude anything definite.
I would expect the fault would not cause any damage outside of the AdBlue system itself - the AdBlue is injected into exhaust stream to neutralize NOx emissions - thus "faraway" from engine anyways.

 

[JimmyAK]

A quick update on my issue. Ringing around a few local dealers, the earliest I could get an appointment to get the fault looked at was end of this week. My closest dealer couldn't get me in until February! If this is the kind of service for engine faults that VW provide, I pity anyone who relies on their van for a living! Anyway, based on the feedback here, I decided it safe enough to continue driving. Just after Christmas the engine light started being accompanied by a 'check DEF' message in the cluster. Despite the AdBlue range showing 11,000 miles I decided to do a small top-up of the suggested minimum amount (7.5L) to see if would make any difference. It didn't, other than the range increased to 18,000 miles.

Now fast forward to this weekend and suddenly the 18,000 miles turned into a 'No Engine Start in 650 miles' warning. So looks like the AdBlue system is well and truly broke. Hopefully it stays that way and doesn't get any worse before I have to drive it to the dealers later this week. I'll post an update with the results.

 

[JimmyAK]

Collected van from the dealers at the weekend after it had been in the workshop all day on Friday. Looking at the job sheet, they replaced the AdBlue pump and 'control board', followed by a full reset of the SCR (Selective Catalytic Reduction) system. All covered under warranty, which is a good job because the final bill was over £700.