Passat 1.9 TDI emergency mode while driving uphill with a caravan

Hello,
I'm facing another tricky problem and I'm not quite sure how to proceed, so I'd like to turn to the experts here for help.
"The following is a description of the error:"
We went on vacation with our Passat, and the 500km drive to get there was trouble-free.

On the way home, after about 250 kilometers and while driving uphill, the engine went into limp mode. There was very little power, and I was pulling a trailer behind me, which made it even worse.
No errors initially. Started the engine with the ignition on. The error disappeared, then the engine accelerated. The error reappeared, and another error was set. The check engine light is on. Okay, here's the translation:

"A couple of times, it continued like that until I set the cruise control to 89 km/h in 4th gear, around 2400 RPM. No error code was triggered, and it even went uphill as long as I didn't have to shift. It just didn't accelerate beyond that speed."
We arrived home, and the following error was read:

000564-Charge pressure control.
P0234: Turbocharger Overboost Condition - Intermittent.

It was very hot that day, a humid 28 degrees! Water temperature is 90 degrees, everything is within the normal range.

Yesterday, I drove without a trailer and really pushed the engine hard going uphill, and there were no errors or loss of power. The warning light turned off on its own, and I hadn't cleared the error code!

First thought: The VTG (variable geometry turbine) adjustment seems stiff, but if that were the problem, wouldn't the error be present now?

Please help, this is our main attraction!

Greetings.
Julian.

The error is only triggered when the difference between the desired value and the actual value is a) sufficiently large AND b) persists for a sufficiently long time.

The latter used to take a whopping 6 seconds with the old AHU / 1Z engine.

But why don't you first check the obvious: the log data with the desired load (LD-Soll) and the actual load (LD-ist). Full load operation at a high speed range of 1,500-4,000 rpm.

Alternative: Oil seepage on the LD pipes.

It's possible that the VTG (Vehicle Stability Control) started to engage due to the high heat (uphill driving + trailer) and the subsequent expansion of the materials. You wouldn't experience the same temperatures driving the car alone. The water temperature was likely over 90°, and the display in the instrument cluster is more of an "okay" indicator. It only starts to rise when the water is above 110° (I'm not entirely sure about that value, but it's definitely not an accurate temperature reading).

"We sometimes encountered this problem with truck turbochargers, and in those cases, we replaced them. In those turbochargers, the variable geometry turbine (VTG) worked by axially shifting the guide vanes, not by rotating them. It's difficult for me to say whether disassembling it would help in your case. If the car is used regularly, replacing the turbocharger would definitely be a good idea." Of course, this is only if the boost pressure is actually too high, and not if the sensor is faulty.

Hi Tobias,

guste100 wrote:

The error is only triggered when the deviation between the target value and the actual value is a) sufficiently large AND b) sufficiently long. The latter used to take a whopping 6 seconds with the old AHU / 1Z engine. But why don't you first check the obvious: the log data with the desired load (LD-Soll) and the actual load (LD-ist). Full-throttle acceleration in the higher RPM range, from 1,500 to 4,000 rpm. Alternatively: Oil seepage on the LD pipes.

I will still perform the LD comparison.
The pressure knob and vintage adjustment move smoothly.
What do you mean by "oil seepage" in the pipes? Sensor dirty?

By the way, this is the vehicle in question.

Passat Estate/Wagon, model year 2005.
Engine code: BKC 1.9 TDI PD 105 hp.

Hi, at 281,000 km, the VTG (variable turbine geometry) can sometimes start to malfunction. In the medium term, avoid driving too cautiously, don't use a power box, and make sure the engine doesn't have any leaks in the charge air system.
Then the charger will also work.

dieselschrauber wrote:

Hi, at 281,000 km, the VTG (variable turbine geometry) can sometimes start to malfunction. In the medium term, avoid driving too cautiously, don't use a power box, and make sure the engine doesn't have any leaks in the charge air system. Then the charger will also work.

I can't say for sure whether the loader has already reached 281,000 miles/kilometers.
It's just uncertain, we're thinking about crossing the Alps in September with the campervan, and if I encounter problems there, then it's good night and back home .

Does anyone have any experience with this vacuum control unit failing?

If I were 100% certain and it was the charger's fault, I wouldn't hesitate to replace the charger for the sake of the device. Finally, before the trip, it got a new clutch and a new flywheel.

Best regards, Julian.

PS: I don't use a powerbox!

The VTG (variable turbine geometry) is controlled by vacuum. So, if the control valve isn't working, you're likely experiencing insufficient boost pressure. I've never seen a control valve hold vacuum when it's not supposed to. With 105 horsepower, your Passat will definitely have its work cut out for it when pulling a caravan .

tobias_ wrote:

The VTG (Variable Turbine Geometry) is actuated by vacuum; in other words, if the control valve isn't working, you have insufficient boost pressure. I have never seen a valve like that hold vacuum when it shouldn't. With 105 horsepower, your Passat will definitely have its work cut out for it when pulling a caravan

.

Was the boost pressure too high at the time of the error? Unfortunately, I couldn't extract that information from the error message because it doesn't specify the expected ("should be") value.

Yes, it's a small caravan, with a total weight of 1100kg, and it works fine, it's okay. It's true that it was better to drive before, with my 2.5 TDI V6, but now it's just a vehicle for hauling materials around the construction site!

Quote:

Was the boost pressure too high at the time of the error? Unfortunately, I couldn't extract that information from the error message because the two values didn't indicate a "setpoint" or "actual" value.

It's kind of, well, it's not explicitly stated in the environmental conditions, but the first value represents the target boost pressure, and the second value represents the actual boost pressure.

Best regards, Rainer.

I'll have to tell my wife that she should drive the car with a bit more of a focus on the engine's RPMs, and I'll probably need to take the caravan out for another test drive soon.

I'll adjust the turbocharger boost pressure sometime this week, and I'll definitely replace the pressure sensor; it doesn't cost that much.

I suppose if I want to drive the Passat, I won't be able to avoid getting a new turbo.

Hello, there's new information from the front lines.
I performed the VTG control today, and everything is working as expected.
After that, I compared the actual boost pressure values with the target values at different engine speeds, and I noticed that, above a certain value, the deviation between the target and actual boost pressure becomes increasingly larger (see attached images).
I will also be conducting this measurement on the highway under load.

Could it be that the LD sensor is faulty within that specific measurement range?

Best regards, Julian.

Hi.

Possibly, the VTG (Variable Transmission Gear) is not opening wide enough, and the adjustment range on the rod is approximately 1 cm.

Can you test measurement block 11 by default?

Quote:

Could it be that the LD sensor is faulty within this specified measurement range?

unlikely.

Best regards, Rainer.

I tested the VTG adjustment today using the measurement blocks, and everything is within the acceptable range. It moves smoothly and visibly back and forth, and the travel distance of approximately 1cm is also correct.
The values also match what VCDS indicates.

Your two screenshots only show two snapshots in time.

I'll repeat myself again:

guste100 wrote:

Why don't you first check the obvious: the log file with the expected LD (LD-Soll) and the actual LD (LD-ist). Full load operation at a high speed range of 1,500-4,000 rpm.

If you were to post the log (instead of screenshots) here, we could also assess the dynamic behavior of your vehicle and, accordingly, offer you more helpful assistance than this aimless back-and-forth.

Greetings.
Guste.

guste100 wrote:

Your two screenshots only show two snapshots. I'll repeat myself again: guste100 wrote: Why don't you first check the obvious: the log file with the expected LD (LD-Soll) and the actual LD (LD-ist). Full load operation at a high speed range of 1,500-4,000 rpm. If you were to post the log (instead of screenshots) here, we could also assess the dynamic behavior of your vehicle and, accordingly, offer you more helpful assistance than this aimless back-and-forth. Greetings. Guste

As you requested, here are two log entries. The first one doesn't quite reach 4000 RPM, while the second one does.

I'm looking forward to seeing your analysis.

Best regards, Julian.