P0299 Audi A4 B7: Common Issues & Solutions

Good day.

I have the following problem with my Audi A4 B7 2.0 TDI (engine code BRD) with 170 horsepower, which is completely original in terms of software and hardware, with no modifications, and has approximately 180,000 kilometers on the odometer:

The vehicle regularly switches to emergency mode under the following circumstances:
- Engine is warm.
- You accelerate through first, second, third, and fourth gear to approximately 100 km/h, then shift directly from fourth to sixth gear and continue accelerating.
At approximately 120 km/h, the engine then goes into a limp mode, with a lightbulb symbol appearing on the display. Interestingly, this error does not occur if you shift through the gears sequentially, beyond 5th gear.

The scenario described above reliably triggers the error, although it has also occurred at speeds of 70-80 km/h and in gears other than the 6th gear. The scenario described above only provokes the error with a near 100% certainty.

The following items were checked using VCDS:
- Error memory of the MSG (Modular Service Gateway) shows:

Quote:

Address 01: Engine Control Module (ECM) Label file: DRV\03G-906-018-BRD.CLB Control unit part number: 03G 906 018 AQ. Hardware version: 03G 906 018 AQ. Component and/or version: R4 2.0l PPD1.3 G 9888 Encoding: 0000072 Company number: WSC 06335 000 00000 text VCID: 74ECA83817B957E69E-8020 "One error found:" 000665 - Charge pressure control. P0299 - 006 - Control limit exceeded - Intermittent. Environmental conditions: Error status: 00000001 Error priority: 5 Error frequency: 3. Lost Count: 40 Mileage: 0 km Time: 0. Environmental conditions: Speed: 2208 RPM Torque: 320.0 Nm Speed: 119.0 km/h 99.45% Voltage: 13.79 V Pressure: 2492.1 mbar. Pressure: 2002.2 mbar

- MWB 7: When the engine is cold, all temperatures are consistent.
- MWB 10: With the engine idling, the charging pressure and exhaust backpressure should be equal within 20 millibars.
- The MWB 10 reading shows 99.9% instead of 100% when the accelerator pedal is fully depressed, but this value is stable, so I think it's acceptable.
- MWB 6: Brake switch bits change state simultaneously; clutch actuation is displayed correctly.
- MWB 11, Basic setting of charging system: The pressure difference in the charging system is greater than 200 mbar between maximum and minimum charge pressure.

Furthermore, the following has already been done:
- EGR valve and entire intake system cleaned and free of debris.
- The N75 was replaced as a precaution (original part).
- The vacuum sensor 03C129061C was replaced as a precaution (not the one on the turbocharger, but the one on the EGR valve).
- The VTG was controlled and monitored via VCDS, and it operates smoothly and moves evenly (more than) 1cm back and forth. The VTG was also manually moved (with the hose disconnected) and feels easy to move and free from any sticking (it pulls against the spring force of the canister).

Not yet done:
- verschandeln the LMM (I don't want to damage it by cleaning it, so I want to rule out other potential causes first).
- Check the VTG vacuum sensor for leaks (does it maintain the vacuum? Test with a syringe). The first attempt failed due to the lack of a suitable hose.
- Checked the DPF for cracks in the monolith structure (I heard somewhere that this could also be a cause).

Today, while the engine was still warm, additional logs (A/B/C) were recorded. These recordings were taken at approximately 1,900-4,100 RPM in 4th gear under full throttle on the highway. During these test drives, the error/NLP did not occur.

Subsequently, the two logs (D/E) that recorded the error were analyzed using NLP. The error occurred as described during gear changes from 4th to 6th gear, followed by acceleration to 120 km/h.

Do you have any ideas about what the cause might be, and which troubleshooting steps (in what order) I should take next?
If other documentation is required, I can provide it.

Thank you very much.
Frederik.

Good morning.

Check the vacuum hose connecting to the VTG (Variable Turbine Geometry) control unit on the turbocharger for any damage.
The other vacuum hoses and distribution boxes must also be airtight.

Then, thoroughly check the entire charge air cooler system for leaks, as these often manifest as hissing or whistling noises under load and oily spots.

Best regards, Rainer.

@fredac
Has there ever been a diagnosis or solution for this issue?
I probably have the same problem.
Best regards, A.

Hi there,
The post is over eight years old and has been closed with no solution.
Start a new topic, introduce your vehicle and the specific problem you're experiencing, along with an OBD scan showing any error messages. "Probably" means something similar.
I'm closing this topic now.
hg
Herbert.