Boost Sensor in ECU?

Hi!

Who can help?
Still searching for the sensor or transistor in the control unit (ECU), but haven't found anything yet.

The control unit's part number is 4A0 907 401 E according to the AAT (Automatic Transmission Tester).


Cu: Marko

Marko wrote:

I'm still looking for the sensor or transistor in the control unit (ECU), but I haven't found anything yet.

Hi.

It's quite simple: the pressure sensor receives the boost pressure through a thin hose that is connected externally.
Okay, so follow the hose further inside; it leads directly to the pressure sensor.

If the engine control unit (ECU) doesn't have any external ports or connectors, you can search for pressure sensors inside until you turn black .

Hi Ulf!

That's exactly it! There's no hose here, so I'm searching and searching...
The sensor is there, but there's no hose connected to it.
Could it be that this parallel question will be asked?


cu: Marko

Marko wrote:

The sensor is there, but there's no hose connected to it. Could it be that this parallel will be assessed?

Hi Marko,

Non-intrusive parallel measurement of boost pressure in the engine control unit:?:
Something like that would be completely new to me (and possibly also raise concerns about potential patent infringement ).

If the sensor is located directly in the intake manifold, it doesn't need a hose. As far as I know, this is the case with the newer 1.9 engines (ALH, AHF, etc.), including those with turbochargers, where a combined sensor measures both boost pressure and temperature.
It usually has 4 connection wires.

Hi Ulf!

I'm sorry, but I have to disappoint you; there are no connection wires included here.
Could it be that the magnetic valve for boost pressure limitation transmits all information to the control unit (ECU)?

Marko wrote:

I'm sorry, but I have to disappoint you; there is nothing here with connection wires. Could it be that the magnetic valve for boost pressure limitation forwards all information to the control unit (ECU)?

Hi Marko,

I'm not familiar with the 2.5 models... However, if that valve has more than 2 electrical connections and is actually supplied with boost pressure (and not vacuum, as with the VTG 1.9 models), I wouldn't completely rule it out.

Hi Ulf!

I'll try the solenoid valve.
I just hope it doesn't blow my turbocharger.


cu: Marko

Hi!
Is it possible that the engine control unit (ECU) determines the ambient air pressure using an internal pressure sensor for altitude correction, or how is the ambient air pressure determined? Does anyone know?

brezelmann01 wrote:

Is it possible that the engine control unit (ECU) determines the ambient air pressure for altitude correction using an internal pressure sensor, or how is the ambient air pressure determined? Does anyone know?

Hi.

Of course, for my tractor, you are absolutely right .

If what's being said about the ambient air pressure is correct, and if this pressure is actually measured within the device itself, then can this [air] be replaced?

'I'm having a problem where, when I turn on the ignition, wait for the glow plugs to warm up, and then start the engine, VAG-COM tells me that the air pressure is only 660 millibars, and the maximum boost pressure is limited to 1570 millibars.'

'However, if I turn on the ignition and wait 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 working too slowly. I'm not sure.'

'There's nothing in the error memory... it's an AFN engine.'

Hello.
I experienced the same issue with a control unit (ECU) with part number 0281001554.
'It showed only 600 mbar on the VAG diagnostic tool when connected to the port without the engine running.'
It is a part of Motorola and is located inside the control unit (but not in every case!).
If the sensor only reports 600 mbar to the control unit, then the maximum boost pressure can only reach 1550 mbar because the boost pressure has a maximum overboost limit of 0.95 bar.
I replaced the sensor and the control unit is working again.

See you, Thomas. / Bye, Thomas.

How did you manage to replace that part?
Is this available as a spare part from Volkswagen?
Did you have to solder anything on the control unit for that?
What did that part cost?
I have a part number 028 906 021 DF STG... is this a Motorola product?

questions upon questions... you've at least given me some hope before .

Hi,
That part is the small black box next to the boost pressure sensor.
It features the following:

2,287,328,608
4023-C
100 kPa

and is soldered with three legs.
Due to the current downtime of the Motorola web server (for maintenance), it is not currently possible to provide an exact product name for the order.

Best regards, Rudi.

Hi.

It would likely be possible to temporarily desolder the small black box and use a multimeter to identify the ground, 5V, and output pins on the circuit board.
Then, solder a diode (e.g., 1N4148) from the positive (+) terminal to the output on the circuit board. Install the sensor and see what ambient pressure is reported via VAGCOM.

If there are no error messages and a pressure of 1000 mbar is displayed, it should be possible to operate normally, but avoid going to high altitudes to prevent overloading the system.

And later, when the opportunity arises, replace the external pressure sensor.

Another very slim possibility is that only one solder joint has come loose, which could potentially be fixed by resoldering around the pressure sensor.

Hi Ulf!

I'm sorry, but I have to disappoint you; there are no connection wires included here.



If I didn't know that the pressure sensor on my ALH was located at the outlet of the intercooler, I wouldn't have found it. Thanks to my Maglite and my patented 'look-around-the-corner' technique (which you learn as an electrician ), I eventually saw it. It's hidden under the water reservoir for the headlight cleaning system. That thing is almost impossible to see...


CU Gremlin.

Hello.
To Blue Bear.
There is something in your control unit.
8,905,958,460
1096-CA
60-120 kPa

I desoldered it from the control unit and soldered in a used one.
It wasn't difficult.
See you, Thomas. / Bye, Thomas.