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P0471 Error: Unlikely Signal - BLS Troubleshooting

 
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jabe2709
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Post28-03-2023, 19:31    Subject: P0471 Error: Unlikely Signal - BLS Troubleshooting Quote

Hello, this is my first post here, please forgive me if I make any mistakes. I have a Passat 3C 1.9 TDI BLS and it has been showing a check engine light for the past 50,000 km. I read the error codes with VCDS, and the first code that appears is always:
1 error found!
001137 - Exhaust gas pressure sensor 1 (G450).
P0471 - 000 - Implausible signal.
Environmental conditions.
Error status: 01100000
Error priority: 0.
Error frequency: 1.
Lost counter: 255
Mileage: 199,799 km
Time: 0.
Date: 2023.03.24
Time: 13:42:02
Environmental conditions:
Speed: 0 RPM.
Speed: 0.0 km/h
(no unit): 40.80
(no unit): -25.50
Air mass: 5.69 g/s.
Temperature: 12.0°C
Temperature: 13.5°C

Then, after approximately 20-50 km (depending on driving style and speed), the following error occurs, including an engine check light (MIL):
8194 - Particle filter, bank 1.
P2002 - 000 - Malfunction - Intermittent.
Environmental conditions:
Error status: 00110000
Error priority: 0.
Error frequency: 4.
Lost counter: 255
Mileage: 199,822 km
Time: 0.
Date: 2023.03.24
Time: 18:38:48.
Environmental conditions.
Speed: 1848 revolutions per minute.
Speed: 86.0 km/h
(no unit) 40.80
(no unit -25.50)
Air mass flow rate: 42.97 g/s.
Temperature: 630.0 °C
Temperature: 22.5°C

What else I can say / What I have already done:
The loading coefficient is always at 15%, but when the errors are cleared and both errors disappear (in just a few minutes), the coefficient quickly drops down to 0.
I've already reset the ash mass to zero and performed a forced regeneration, but nothing has worked. I've now adjusted the ash mass back to a value appropriate for the mileage, according to the formula.
'The fuel consumption is normal, and as I mentioned before, I've been dealing with this issue for a long time, but the engine still has full power.'
I replaced the DDS sensor and re-paired it (multiple times, both manually and using VCDS). The error kept recurring. I blew through both lines, and they felt clear.
'What I find very strange, and what I believe is the cause, is that the differential pressure reading for the particulate filter in measurement block 67 of the engine control unit always shows -40.80, and the offset differential pressure shows -25.5. This is true regardless of whether the engine is on or off, under full load or idle, with a new or old DPF sensor, and even after recalibration, it remains the same. Does anyone have any ideas what this could be? I suspect an electronic fault, perhaps? How and where could I check the three electrical wires that run from the DPF sensor to the engine control unit? Or do you think it's something else?'
Thank you very much in advance.


Translated on 30-07-2026, 18:32.
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Post28-03-2023, 20:50    Subject: P0471 Error: Unlikely Signal - BLS Troubleshooting Quote

Autoscan.
Sommer: A4 B5 Avant 2,5 TDI Quattro Facelift (AKN silber)

Wartet auf H Kennzeichen: A4 B5 Avant 1.9 TDI Quattro (AFN Schwarz)

Winter: A4 B5 Avant TDI Quattro (AFN rot)

Alltags Spardose: Audi A2 1.4 TDI (AMF Silber)


Translated on 30-07-2026, 18:38.
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