VW Phaeton: P0299 Turbo Boost Problem & Power Loss

Hello everyone.

I have a Volkswagen Phaeton 3.0 TDI from 2008 with 171 kW, engine code CARA.
I've done a lot of work and replaced many parts. So far, the car runs without problems except under full load. In second and third gear, when accelerating at full throttle, there is a loss of power, which only returns when you lift your foot off the accelerator pedal. If you keep your foot on the gas for longer than 5 seconds or more, the error code P0299 "Boost Control System - Limit Below" appears.
It's rarer in the 4th gear and doesn't happen at all in the 5th gear. I've made 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!
Attached are the log files; hopefully they contain the necessary information.

Best regards,

Hi,

Okay, the charging behavior appears to be good under normal conditions. The mass airflow sensor (MAF) values also seem reasonable.

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

Also, also check the wiring from the boost pressure sensor as well. It's possible that damage caused by rodents, chafing, or a loose connector (depending on the engine angle) could be disrupting the boost pressure signal and explaining why it changes with different gear selections.

In the lower gear ratios, the engine/transmission block tends to tilt slightly more when accelerating due to the different gearing. So, check all cables and connectors that might be affected by this tilting.

Best regards, Rainer.

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

Nnu original air filter.

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

Turbocharger assembly complete with actuator motor for variable geometry turbo (VTG) from BR-TURBO. New, not refurbished.

New Bosch turbocharger pressure sensor.

Intercooler system checked; pressure and smoke test are leak-free.

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

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 how they are installed. Injector number 6: new seals and cleaned in an ultrasonic bath.

Catalytic converter endoscopy.

The new DPF was defective internally, including the differential pressure sensor. Everything has been reset.
Anmerkung: Vor Kat.Temperatursensor, Vor/Nach DPF Temp.sensor, Differenzdruck vorne, Russ/Asche Beladung/Masse diese Parameter zeigten immer die gleichen Werte egal was man machte wie eingefroren. Habe ein Reflash des MSTG machen lassen danach waren alle Werte wieder Plausibel. Entweder hat der Vorbesitzer da was rumgespielt weil das passiert nicht von selber. DPF inspected with an endoscope.

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. This may or may not be related to the repairs done by the previous owner, or perhaps it's leaking through the overflow opening?
See the invoice Screenshot.

Hello,

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

Is the synchronization angle correct? Check the wiring harness.

Best regards, Rainer.

Hello.

Besides code 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 specifically?
Can the synchronization angle also be checked using VCDS? If so, which control modules and diagnostic addresses are required?

Best regards,

Hello,

für Dein Motorsteuergerät hast Du keine Steuergerätebeschreibung, es gibt inzwischen ein Datenstandupdate für VCDS, so zumindest bei mir. AlsPlease update or refresh.

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 for it at the top of the selection list.

Best regards, Rainer.

It's strange, but that seems to be the way it is. Yes, it probably needs to be updated.
But it doesn't show anything, so I mean 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.

Regarding the wiring harness, which one 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 there,
Just a thought - wouldn't the topic of synchronization angles be more relevant for a PM motor? The CARA would have to be a CR (capacitor run) motor.
hg
Herbert.

Hi Herbert,

The valve timing must be correct regardless of the injection system. It's even better if this 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 unusual. By the way, I've already done this three times.

Note: As far as I've read, the synchronization angle (valve timing) isn't limited to just the 3.2 V6 engine; it also applies to other engines like the 3.0 TDI.
I have to do it manually, so I need to disconnect things and adjust the OT (Optical Transceiver).
Remove the left and right covers and check them.
Has anyone checked this on a 3.0 TDI using VCDS before, if it's even possible?

Do synchronization angles (valve timing) have anything to do with the P0299 code, which indicates that the boost pressure control has exceeded its limit?

Best regards,

Hi there,
"My assumption regarding the CR TDI was about the synchronization angle. The injection timing of the high-pressure pump is synchronized with the crankshaft (KW) when properly adjusted. Only the camshaft (NW) is fixed in place."

Wenn es wirklich um den Fehler "Ladedruck Regelgrenze unterschritten" geht - der Fehler wird gesetzt, wenn bei gegebener Luftmasse zuwenig Ladedruck erreicht wird (oder gemessen wird). 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-DataScope work? We're currently in a car with VCDS version M.F.T 23.3.1. Is the K-DATA Scope a separate device, or can you access it through existing logs?

Please help! Thank you!!