P0299 Full Load Performance Drop VW Phaeton 3.0TDI, Engine Code: CARA

Hello everyone.

I have a VW Phaeton 3.0 TDI from 2008 with 171 kW and engine code CARA.
I've done a lot of work on it and replaced many parts. So far, the car runs without any problems, except when under full load. In 2nd and 3rd gear, when accelerating at full throttle, there's a loss of power, which only returns when you lift your foot off the accelerator. If you keep it on for at least 5 seconds or more, the error code P0299, "Boost pressure control, limit below," appears.
It's rare to find it in 4th gear, and it doesn't exist at all in 5th gear. I've taken several logs using VCDS, hopefully you can help me!
Description of log files:
GOOD = No performance degradation.
BAD = With performance degradation.

Best regards,

Hello,

Please upload the logs as well.

Best regards, Rainer.

Hello Rainer, thanks for the feedback!
Please find the log files attached. I hope they contain the necessary information.

Best regards,

Hi,

Okay, the charging behavior appears to be good under normal conditions. LMM values are also useful.

A possible issue could be with the VTG (Variable Turbine Geometry) adjustment (e.g., a defective or stiff mechanical actuator). Alternatively, there might be a foreign object in the air filter housing or in front of the intake opening, such as a forgotten cleaning cloth that is occasionally sucked in.

Also, also check the wiring from the boost pressure sensor as well. It's possible that damage from rodents, chafing, or a loose connector (depending on the engine's angle) could be corrupting the boost pressure signal, which would explain the dependence on the gear.

In the lower gear ratios, the engine/transmission block tends to tilt slightly more when accelerating due to the different gear ratio. Okay, let's check all the cables and connectors that could be affected by the engine position.

Best regards, Rainer.

Hello Rainer, thank you for your analysis!
Okay, here's how it was done:

Nnu original air filter.

New, original intake manifold before the turbocharger, including pulsation damper with hose for venting.

Turbocharger complete with actuator for VTG (Variable Turbine Geometry) from BR-TURBO, NEW, not refurbished.

New Bosch turbocharger pressure sensor.

Intercooler system checked, pressure/smoke test passed (no leaks).

Vacuum lines from the brake booster to the check valve and to the EGR pressure control valve, new, original Audi.

Pressure sensors, including new ones from AGR and RIDEX, have been temporarily replaced with original parts, which worked well.

The injector configuration didn't match what I read out with the diagnostic tool, so I reprogrammed it. Now all the IMA numbers match the installed injectors. Injector No. 6: New seals installed and cleaned in an ultrasonic bath.

Catalytic converter endoscoped.

The new DPF (Diesel Particulate Filter) was defective internally, including the differential pressure sensor. Everything has been reset.
Note: The readings from the pre-catalytic converter temperature sensor, the pre/post DPF temperature sensors, the front differential pressure sensor, and the soot/ash load/mass were all showing the same values, regardless of what was done, as if they were frozen. I had the MSTG reflashed, and after that, all the values were plausible again. Either the previous owner messed with something, because this doesn't happen on its own. DPF endoscopically inspected.

The previous owner had the following work done, as shown in the photo. It should be noted that I recently topped up the coolant to the MAX level, and after driving approximately 150-200 km, mostly on the highway, the level has dropped by about 1 cm. Could it be related to a previous repair, or is something leaking out through the overflow opening?
See the invoice Screenshot.

Hello,

Is there any other error code besides P0299 in the engine control unit?

Is the synchronization angle correct? Check the wiring harness.

Best regards, Rainer.

Hello.

Besides P0299, there are also the codes listed in the attached test report.

The sporadic errors have occurred approximately 3 or 4 times since April 2023.

You only see it when you read the error codes; otherwise, it doesn't show anything on the instrument panel.

Do you mean the main wiring harness that goes to the MSTG, or which one?
Can the synchronization angle also be checked using VCDS? If so, what are the material numbers, etc.?

Best regards,

Hello,

For your engine control unit, you don't have a device description, and there's now a data update available for VCDS, at least that's what I've experienced. Okay, updating.

Please read the fault memory of the engine control unit again.

The synchronization angle should be found in the advanced measurement data from the engine control unit; you can search (type) at the top of the selection list.

Best regards, Rainer.

It's just weird, that's how it is. Yes, it definitely needs to be updated.
But it doesn't show anything, meaning there are no errors or anything like that.

I will take a closer look at the synchronization angle.

Attached is the order document indicating where the MSTG was flashed.

Which wiring harness are you referring to?

Best regards,

Quote:

Regarding the wiring harness, which one are you referring to?

All cables and connectors to the relevant sensors and actuators, including the mass airflow sensor (MAF), boost pressure sensor, VTG actuator, EGR valve, and all temperature sensors.

Hello Rainer,

Okay, I'll do that this weekend.
Check for cable breaks or damaged insulation, and see if the connector connections are possibly oily. Unfortunately, it's not easy to access all of the sensors.

Best regards,

Hi,
Just a thought - wouldn't the topic of synchronization angles be more relevant for a permanent magnet (PM) motor? The CARA should be a CR.
hg
Herbert.

Hi Herbert,

The valve timing must be correct regardless of the injection system. The better it is if these can be checked without any mechanical work.

Best regards, Rainer.

Hello everyone.

Okay, so far as I can see and reach, all the cables and connections seem to be fine. Nothing seems out of the ordinary. By the way, I've already done it three times.

Note: As far as I've read, the 3.0 TDI engine doesn't only have the same synchronization angle (valve timing) as the 3.2 V6 and other engines.
I have to do it manually, so I need to adjust the settings and turn the potentiometer.
Remove the left and right covers, then check.
Has anyone checked this on a 3.0 TDI using VCDS, if it's even possible?

Do synchronization angles (valve timing) and the P0299 fault code related to "boost pressure control, limit exceeded" have anything in common?

Best regards,

Hi,
My assumption regarding the CR TDI was about the synchronization angle. The injection sequences of the high-pressure pump are synchronized with the crankshaft (KW) when properly adjusted. The NWs are only being marked.

If the issue is truly related to the "boost pressure limit exceeded" error, this error occurs when, given a certain amount of air mass, the boost pressure is too low (or is measured as being too low). "That is to say, searching for..."
- Leak between the turbocharger and the cylinder heads;
- Incorrect measurement of boost pressure (sensor, wiring, connector, if applicable: sensor cable).
- possibly: Incorrect measurement of ambient pressure (sensor, wiring, connector).
Unfortunately, your log is missing a marker indicating the start of the error.
hg
Herbert.

"How does the K-data Scope work? We're currently in a car with VCDS version M.F.T 23.3.1. Is the K-DATASCOPE a separate component?" Can one access the existing logs through that interface?

Please help! Thank you!!