Boost Pressure Sensor (Engine Control Unit)

I was wondering how a faulty boost pressure sensor manifests itself.
According to Ulf's report, the turbocharger pressure may be too high or too low.

How exactly do pressure sensors fail?
Can this be caused by strong vibrations or impacts to the STG (subframe)?
and how does that happen with the pressure sensor housing?

Can the pressure sensor be protected by soldering a diode onto the sensor signal, and what effect does this have?
Could damage occur due to the heat generated? (12V soldering iron, maximum 3-4 seconds of contact with the material being soldered).

What else, besides vacuum hoses, VTG (Variable Turbine Geometry), pressure transducers, and intake manifold temperature sensors, can be measured?
Should the sensor be adjusted to a low (0.4-0.5 bar) boost pressure?

Ibiza 6k
1.9-liter TDI

Hello,

It sounds like you don't have an external boost pressure gauge. That's the most important thing to have when you're soldering things. Have you already reassembled everything?

I don't think it will break due to a short soldering process.


What else it might be, the search function will tell you. You won't be able to read much more this year, as you'll find out there.

Good luck, Rainer.

Yes, a boost pressure gauge is installed, and someone even posted about it here in this forum.
It has a range of -1 to 2.5 bar.
Normally, the maximum boost pressure for a 1.9L TDI engine should be 0.9 or 1.0 bar, but mine is only reaching 0.4 bar.
from 1800 to 4500... so, no weak LMM.

It started when I installed the larger turbo.
After that, of course, increase the fuel quantity as adjusted by the tuning box, along with increased boost pressure.
It was working great until I drove over that damn pothole.
'For 1.5 months, I drove around trying to find the cause of the error message indicating the car was in 'limp mode'.'
Finally, I opened up the control unit and removed the insulation from...
I removed the pressure sensor.
(In the meantime, the pressure transducer and mass airflow sensor have been replaced; //sigh *frustration)
Unfortunately, a solder joint has become detached and failed.
I desoldered all the cables and reconnected them to match the original configuration.
would correspond to.

Since I can't think of any other components that might be related to the problem, and in my search...
'I can't find anything else on the forum besides vacuum hoses, VTG (Variable Turbine Geometry), and altitude sensors.'
That really leaves very little left.
Perhaps the pressure sensor is not damaged by soldering, but by a physical impact.
become?

The best is yet to come.
I was at Bosch in Vienna, and they told me, 'This part is no longer being produced, but we still have some in stock.'
'Let's talk to the gentleman in the workshop about it.' ... 'That part is no longer being produced, but we could get it for 170 euros.' ... WTF?? 170 euros? ... That part isn't a washing machine, after all.
'Can't even cook, or am I missing something?'

I'm currently browsing www.sensortechnics.com; they seem to have cheaper parts, but I'm not entirely familiar with sensors myself.
Does anyone have any advice?

The part in the ECU has the number...
BOSCH 0 273 003 210
0.4V at 20 kPa.
4.65V at 250 kPa.

'Thank you, Peter.'

Hi,

Take a look at the Motorola MPA sensors for automotive applications. They cost around 20-30 euros and have a linear characteristic curve that can probably be easily adjusted, or might even be correct as is - it's possible they are using the exact same ones.

Take a look at my LDA article.

Best regards,

Jan.

neubaupe wrote:

Yes, a boost pressure gauge is installed, and it has even been posted about here in this forum. It has a range of -1 to 2.5 bar. Normally, for a 1.9L TDI engine, the maximum boost pressure should be 0.9 or 1.0 bar, but mine is only reaching 0.4 bar from 1800 to 4500 RPM... so it's not a weak mass airflow sensor.

First, connect VAGCOM and check the values that the engine control unit is receiving from the sensor.
If you only read 1.4 (absolute value) from the sensor, which is the expected value for the LDA, then the sensor is okay, and the problem lies somewhere between the control unit and the turbocharger.

Since the pressure is constantly regulated to 1.4, I assume that the sensor (or its external circuitry) is faulty and that the reading is resulting in 2 bar absolute.

@ulf
As I mentioned, I've already replaced the pressure sensor, and the vacuum hoses as well.
VTG has been reviewed for the 20th time.
Unfortunately, I don't have access to a VAGCOM device, and after it failed to read the memory for the third time.
Since I was essentially forced out of Seat, I don't want to go back there.
I've also been considering getting the VAGCOM 'self-assembly' kit, but some...
People never get smarter.

!! @ Jan6k
The MPX 4250A either fits perfectly, or Volkswagen is actually using it.
I wanted to ask you if you only purchased the basic model 'A'.
How did you connect the hose for measuring?
The datasheet states that there is a case available for it, but unfortunately, it cannot be ordered from there.
... or was one included? It only says 'C867' here.

peter

Hi,

I wouldn't be surprised if it's exactly him.

Regarding the casing:

"Please read the datasheet carefully. Quite far back, you'll find the table of model designations and their corresponding housings – you need the 867B, which, according to my datasheet, has the commercial name MPX4250AP. If it ends with just "A", it's the bare chip. If it ends with "AP", it has a housing to which a rubber tube can be attached (see the picture in the datasheet)."

I installed exactly the same one in my LDA (laser diode array).

I bought it in Berlin from Segor (www.segor.de).

Best regards,

Jan.

@ Jan6k

Thank you very much!
I have already placed an order with Segor.
An incredible variety seems to be available there, as shown in the pictures from the location.
show a room/hall full of cabinets
Unfortunately, something like that, in that size and in that form, doesn't exist in Vienna.

Thanks again, I'll get back to you when it's installed and I have some results.

msfg! Peter

It might also be advantageous to bid on and purchase an entire control unit on eBay.
I got my second one there too, and it also cost 30€.

I would actually have it properly chipped, not some cheap solution with resistors and a power box. There's a very good tuner in Vienna.

ulf wrote: Since the pressure is regulated to a constant 1.4, I suspect that the sensor (or its external circuitry) is faulty and is reading a pressure of 2 bar absolute.

I have now installed the pressure sensor, but I'm still having the problem with the low boost pressure.
New sensor with no diodes in the sensor signal: 0.45 bar boost pressure under full load.
New sensor with diodes on the sensor signal: 0.55-0.6 bar boost pressure under full load.

Can we conclude from this data that there is a problem with the external wiring of the pressure sensor?
If so, does that leave me with the only option of installing a new ECU (Engine Control Unit), or is it possible to identify and fix the problem?

@ Henrik
It's great that some STGs (special transport containers) for the AFN (Armed Forces Network) are being auctioned on eBay.de, and the prices are reasonable, but unfortunately, most sellers only ship to Germany. Do you have any other suggestions?

neubaupe wrote:

New sensor with no diodes on the sensor signal: 0.45 bar boost pressure under full load. New sensor with diodes on the sensor signal: 0.55-0.6 bar boost pressure under full load. Can we conclude, based on this data, that the external manipulation of the pressure sensor

"worked"?
Possibly.
However, there are other possibilities:
For example, if the ambient pressure sensor provides readings that are too low, the control unit may incorrectly interpret this as a need to engage the "high-altitude brake" to protect the turbocharger.
Or the ADC, which processes the boost pressure signal, might be faulty.

To make real progress and get to the root of the problem, you really need to use VAGCOM. Anything else is just guesswork.

Please provide the text you would like me to translate from German to English. I will then provide only the translation, without any explanations. Also, please include the text that mentions "Murphy's Law of blind searching" so I can translate that part as well.

If there are x possible causes for an error, and you eliminate them one by one, then the (x)th possibility will be the actual cause.

ulf wrote:

neubaupe wrote: New sensor without diodes on the sensor signal: 0.45 bar boost pressure under full load. New sensor with diodes on the sensor signal: 0.55-0.6 bar boost pressure under full load. Can we conclude, based on this data, that the external manipulation of the pressure sensor "worked"? Possibly. However, there are other possibilities: For example, if the ambient pressure sensor provides readings that are too low, the control unit may incorrectly interpret this as a need to engage the "high-altitude brake" to protect the turbocharger. Or the ADC, which processes the boost pressure signal, might be faulty. To make real progress and get to the root of the problem, you really need to use VAGCOM. Anything else is just guesswork. Sure, here is the translation of the text from German to English: "Please note Murphy's Law of blind searching:" If there are x possible causes for an error, and you eliminate them one by one, then the (x)th possibility will be the actual cause.

I didn't even know that an AFN (presumably referring to a specific device or component) has an ambient pressure sensor.

It's possible that there's still some kind of data logging or evaluation happening within the control unit.
"defekt" is what I think Ulf meant.

I didn't even know that a VW (Volkswagen) has an ambient pressure sensor.

It's possible that there's some kind of data logging or analysis happening within the control unit.
defekt is, like Ulf probably meant

Ugh... thank you!
I was already wondering where I should even start looking, and why I can't find anything!
I believe the AFN doesn't have an ambient pressure sensor, or at least I can't find any information about it online.

If that is the case, I'm just glad, as it allows me to rule out another component.

Do you mean by 'some kind of logistics evaluation' the evaluation within the control unit?
I think a possible solution to check the engine control unit (ECU) would be to visit all the scrap dealers in Vienna and the surrounding area and replace it with a different one.

Thank you very much for the tips.

I will get back to you again if there is anything new .

peter

neubaupe wrote:

I think the AFN doesn't have an ambient pressure sensor, at least I can't find any information about it online.

So, my AFN definitely had one, and it's located in the ECU (Engine Control Unit).

neubaupe wrote:

It's great that some STGs for the AFN are being auctioned off on e_b_a_y.de, and the prices are also reasonable, but unfortunately, shipping is usually only available to Germany.

While it usually says "Shipping only to Germany," I've found that so far, every time I've inquired, they've shipped to Austria.

ulf: So, my AFN definitely had one, and it's located in the engine control unit (ECU).
Sure, the AFN has one, but it's unfortunately difficult to recognize.

For DIY enthusiasts only:
I was able to purchase a second gearbox on eBay for about 50 euros.
After having the engine control unit (ECU) adjusted to bypass the immobilizer (the search function was really helpful),
I had the normal boost pressure of 0.9 bar, which is typical for an AFN engine.
I can only conclude from this that...
Does starting the AFN (presumably a vehicle system) depend on whether the boost pressure sensor has a connection to the engine control unit (ECU)?
(Cold solder joint, interruption), which can then have serious consequences for the control unit (ECU).
Either the circuit to the pressure sensor is damaged, or something else within the control unit (ECU) is misconfigured. In any case, after such an event, it no longer regulates to the normal boost pressure (but instead regulates to a lower pressure, about half).

Best regards, Peter.

PS: Thanks again to everyone who tried to help me solve this problem.