Ladedrucksensor im STG? | Posts 16+

@ Rudi & ulf & zeka

Okay, thanks everyone. I'll try to fix my device this weekend, and then all I need is to find a new sensor somewhere.


best regards, BB

Hello,

So, if what a VW master mechanic 'happened to tell' me is true...
Then at least the engine control unit in my AJM-115PS PD (Passat Variant) has it.
'This altimeter can apparently also be queried from inside.'

At the same moment, he also told me that these values are useless (or that you won't receive any parts from Volkswagen for the workshops).

It would also explain why my Passat is experiencing a loss of power, which mainly manifests as a lack of acceleration. I've been searching for the cause for about 60,000 kilometers now.

(He has one on Mondays, but not on Thursdays, and on odd days she's there... I've given up trying to figure it out.)

I assume that the problems are related to various sensors and potentially loose solder joints.

I'm generally optimistic, but sometimes it just gets to be too much.
It's a waste of money that competent workshops are charging me to find these parts, and I'm still searching for a reliable exploded diagram showing all the hidden sensors.

I didn't want to discourage anyone, but this needed to be said.
I've noticed that these hidden flaws are increasingly coming to light, and Volkswagen is too incompetent and complacent to even bother looking for errors!

Regards,

Thorsten, the suffering one.

Hi,
The 'altitude sensor' or 'atmospheric pressure sensor' can be (also in the AJM).
Record the data using VAG-COM in at least two locations.
1. In display group 0 (this only works with a VAG-COM device that is properly configured).
When the engine is idling, the sixth value from the left should read 183-223 (which corresponds to 910-1110 millibars).
In ad group 10, the second value from the left represents the value measured by the altitude sensor in millibars.

The specifications for the Zeka sender match an MSA12-STG; I copied the number above from an MSA15. It's likely that only the designations are different, because the senders look absolutely identical, and the sender from the MSA15 can also display values above 100 kPa.
I also noticed that the sensor in the MSA12 was additionally glued with silicone (as was the one in an early TDI engine control unit).
'In this design configuration, these pressure sensors are either no longer manufactured or are not available on the open market. However, there are some electrically comparable sensors from Motorola (e.g., MPX4115, 0..115 kPa).'
Getting started with sensors is the page http://e-www.motorola.com/webapp/sps/site/taxonomy.jsp?nodeId=01M939346219036.
You can download an overview from http://e-www.motorola.com/brdata/PDFDB/docs/SG1010.pdf.

Best regards, Rudi.

Hi Gremlin!

I'm sorry, but I have to disappoint you on that as well!
Because I've already disassembled the coolant system and all the hoses countless times, and I haven't found any pressure sensors, nothing at all.


cu: Marko

Today, I disassembled my pressure gauge and desoldered the altitude sensor. It's a 1096-cb with a range of 60-120 kPa. As suggested, I installed a diode in its place, but unfortunately, it didn't work. In fact, it now displays 400 mbar .

My question is: the Motorola sensor MPX4115 displays values from 0 to 115 kPa. Could using this sensor instead of the original cause problems, considering that the ranges are different (60-120 vs. 0-115 kPa)?

best regards, BB

p.s.: Oh yeah... finding the GND wasn't difficult... but how do you best determine where the +5V and output are located? (maybe I just did something wrong )

Hi,

Mass is one of the external pins of the sensor. 5V is located in the center.
The specified range for the built-in sensors should be treated with caution. I compared the two types, and the voltages were approximately the same (it's possible that one specifies the total range and the other specifies the nominal value).
What did the sensor's solder joints look like? If the sensor's actual measurement range is indeed 60-120 (0..4.7V), then the value displayed in case of a fault would correspond to approximately 0V.
Assuming the above assumption is correct, the MPX would always report an air pressure that is too high (and the error would increase as the actual air pressure decreases).

Best regards, Rudi.


Sure, here is the translation of the text from German to English:

'Addendum:'

You can also use a potentiometer for testing purposes (e.g., 10k). Connect one end to 5V, the other end to ground, and use the wiper as the output. Then, check the displayed value with VAG-COM. Adjust it until 1013 mbar is displayed, remove it (carefully, avoid twisting), measure the resistances of the potentiometer, install two matching individual resistors, and drive in the mountains with a controlled throttle .
Since the faulty sensor didn't generate any error codes, the trick of using two resistors should work just as easily.

Addendum two:

Since you observed 400 mbar with the diode, the sensor cannot output 0V at 60 kPa (and likely doesn't start outputting a signal until above 0 kPa).

ttns4 wrote:

Hello, So, if what a VW master mechanic "happened to tell" me is true... Then at least the engine control unit of my AJM-115PS PD (Passat Variant) does. "This altimeter can apparently also be queried from inside." At the same time, he also told me that these values are useless (or that you won't receive any parts from Volkswagen for the workshops).

"... consider switching workshops if the master mechanic doesn't know why a height gauge is needed in the engine control unit (ECU). It's obvious he can't read! The training materials from Volkswagen clearly state:..."
"The altitude sensor reports the current ambient air pressure to the engine control unit. This pressure depends on the geographical altitude. The signal is used for an altitude correction in the turbocharger boost control and exhaust gas recirculation systems."
If you don't understand this, you should quit your job!
By the way, I vaguely remember that the operating manual mentions something like "...the engine power is reduced at high altitudes...".
The altimeter is not a special feature of your STG; it's standard!

To return to the actual pressure sensor we were looking for: It is located on the injection rail of the AAT (air intake manifold), next to the valves for EGR (exhaust gas recirculation) and LDR (lean direct reaction). Unlike these two, its connecting cable has three wires.
Christian.

christians wrote:

To get back to the actual pressure sensor we were looking for: It is located on the injection nozzle housing of the AAT, next to the valves for LDR (Lambda Diesel Retrofit) and AGR (Abgas Rückführung). Unlike these two, its connection cable has three wires.

Hi Christian,

Finally, someone has "found" that thing.

'However, if I turn on the ignition and wait for 15 seconds before starting the engine, everything is okay. The ambient air pressure then reads approximately 970 mbar, and the boost pressure is limited to the normal 1970 mbar. So, I think there might be a problem with this sensor in the control unit. Perhaps it's only detected during the self-test of the control unit after 15 seconds, and then somehow ignored. Or maybe the sensor is just working too slowly. I'm not sure.'

There's nothing in the error memory... it's an AFN [/quote].

Hello Bluebear, I also tested the 15-second thing at my place once...
Conclusion: With my AJM PD engine with 85 kW, I find that it performs significantly better in terms of acceleration and pulling power somewhere between approximately 140 and 180 km/h.
I have the feeling that the elasticity is definitely much better.

'Does anyone happen to have a picture of the inside of the control unit, showing where this component is located? I'm not keen on disassembling everything for no reason.'

However, I've noticed several times now that in this nice weather, our car comes to a stop at around 180 km/h, even after waiting for 15 seconds.

(It's rarely possible to drive on it right now, but if the road is clear, you can use tires with a maximum speed rating of around 190 km/h.)

I'm starting to give up.

'My car has now reached 90,000 km, which means I've been driving it for about 65,000 km... to be honest, the service department at the dealership really messed things up for me.'

I'll check the engine control unit (ECU) number again soon to ensure everything is complete.

In my case, I'm quite sure that Ulf is very close to the solution because the symptoms might not always appear when the temperature changes; sometimes they show up differently when restarting. It could really be a cold solder joint or something similar.

Isn't that a 'latent defect that exists even outside the warranty period???'



Sure, here is the translation of the text from German to English:

'Dear Bertil,'
'Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag.'

The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day.

Thank you for the information, Bertil . I also figured it out, but finding a workshop is difficult; unfortunately, I've already contacted most of them.

...And I'm slowly starting to have problems with my family (I can't blame them, I'm financially and emotionally drained from the troubleshooting process and all the associated stress...).

Furthermore, I find it dangerous that there is no output when you demand it!

As I said: I've given up on it now.

Maybe I'll get lucky someday by chance.

If we don't hear from each other before Christmas:

Merry Christmas and a Happy New Year!
Thorsten.

HI!

The hose that runs from the intake manifold down to the (sensor) has been found and measured.
The voltage is 1.65V when the device is at rest.
Just put a resistor in between and that's it?


cu: Marko

Hello,

I'm reviving this thread because I'm having a similar problem.
The engine control unit (ECU) is a 028 906 021GG from an AHU engine.
"Control unit defective" error message. Atmospheric pressure sensor malfunctioning intermittently.

I measured 418 mbar when the component was desoldered, and 693 mbar (replacement value) when it was soldered in or connected to a +5V output.
I already had a diode installed, but it always ends up being the replacement value (i.e., the voltage is too high).
Unfortunately, I don't have a working replacement sensor.

If I touch the +5V and output pins (wires soldered to them) with my fingers, I get a reading of approximately 1100 mBar, which seems correct. If I increase the pressure between my fingers, the short-circuit replacement value for the positive terminal reappears.

What resistance value/voltage value do I need at the output to simulate approximately 1000 mbar? I tried measuring the voltage drop across the skin, but the resistance of the voltmeter itself makes the measurement impossible.

The characteristic curves of pressure sensors are generally linear.
Given a suspected measurement range of up to 1.2 bar at approximately 4.5V, it is estimated that 1000 mbar corresponds to roughly 3.7V.

If you have a potentiometer with a total resistance of approximately 10-100 kOhms on hand, you could try soldering it in and adjusting it until you see the desired fake value in the diagnostic readings.

Okay, I've figured it out – according to VCDS, using two 1N4001 diodes gives me an equivalent value of 1162 mbar.

EDIT: Attention - in this case, the pin configuration is as follows...

center pin +5V
left signal out.
right GND

Hello everyone!

vwSchrauber wrote:

... EDIT: Attention - in this case, the pin configuration looks like this... left +5V center signal out right GND

@vwSchrauBär:
Something seems wrong if that image represents the final test setup...
Both diodes would be reverse-biased from +5V to the OUT pin.
Could it be that the LEFT pin is the output and the center pin is +5V?
Where does the rightmost connecting wire go on your setup? You actually don't need that wire for this circuit, especially if it's connected to ground.

Best regards from Munich!

I've now implemented a 4k3 pulldown on the signal output. This results in a pressure reading of 979 millibars, which is a realistic value for an altitude of approximately 300 meters above sea level.

Has anyone got an original data set for the 021GG that I could use? I'd like to check when the ATM pressure-dependent limits start to apply.

"@Bear: You correctly identified it, I have corrected it. "