T4 2,5 ACV Ignition Lock or MSTG (Solution)

Hi there,

I just saw a 1999 T4 with the engine code ACV parked on the lot.
Vehicle started on Sunday afternoon and shut down again after 1 second.
He knocked on the steering column cover and he ran again.
Yesterday, I encountered the same problem again, but this time the error persisted.

I have read out the MWB in the starting lock, the key is recognized and released.
If I remove the transponder, I will also see this in the MWB.

The attempt to read the MSTG failed because it was no longer accessible. I had a spare relay, 109, and immediately swapped it out.
The relay is also pulling.

The error actually clearly points to the start-stop system, but the key is being recognized.
Where could the dog be buried?

Greetings

Quote:

Where could the dog have buried it?

If the blow to the steering column wasn't an accident... E-Part ignition switch, connector loose, etc.

The "Immobilizer" is a functional component of the MSTG (or, to put it another way,
(the part that prevents the car from starting)
If everything is okay, the MSTG will query the STG of the WFS at Key Level 2.
That then transmits back that a valid key is present in the ignition lock.
Then we started, and the engine remained on.
Your problem might be that MSTG and WFS are not communicating. That is in favor of
that you also cannot reach the MSTG regarding the diagnosis.
In case of emergency, re-establish contact with the MSTG diagnostic team.

Hi Micha

Thank you for the responses.

Does anyone have a wiring diagram or more information about the diagnostic lead?
I found "Grau/Weis" on Google, and that also makes sense, as it is also the case with the OBD connector.

It should be sufficient if I have MSTG install a new line directly to the potential distributor under the steering wheel, or preferably directly to the OBD-port?

Greetings

Tip: The engine control unit must be securely fastened to the metal casing, not just loosely attached. Had a similar problem before (mass-related issues).

I'm going to find the pinout for the engine control unit for you.

Best regards, Rainer

dieselschrauber wrote:

Tip: The engine control unit must be securely fastened to the metal casing, not just loosely attached. I've had a similar problem before (mass-related issues).

But this is actually impossible, the part was completely stored/attached in plastic in the T4.

Unfortunately Please still consider potential errors from the control unit. The control unit is available with a metal casing and with a plastic casing.

Thank you to TDI-GTI-4-Motion for the tip that only the plastic version of the T4 exists.

No
The control unit is located under the battery in a housing.
made of plastic.
Nevertheless, check the supply.

No, the STG also comes with a metal casing, but the bracket that it is attached to is made of plastic and has no connection to the ground, so it definitely does not have a ground connection.

or so. You have the box standing

Thank you, guys

If there are problems with the power supply, he shouldn't be able to use it at all, right?

Can I directly connect the K-line from MSTG to the OBD-connector or should it go through the potential distributor under the steering wheel? I haven't done anything like that before.

Edit: K-line is Gray/White

I would first directly test the OBD connector, because from there you have
You need to establish a connection to the WFS storage (which you require).

K-line up to WFS OK.
Placed directly on the OBD port, without success.
Mass is, however, not present on pin 45.
The cable from Pin 45 to Relay 109 is also fine, and the relay is pulling.

The K-line on the WFS control unit is active twice, one goes to the control unit and the other goes to the distributor and from there to the OBD-Dose.
But there is no connection between the two cables on the WFS control unit.

Would the MSTG really not start at all without power? Wouldn't it not even turn on for a single second?

Quote:

Would the MSTG really not start at all without power? Wouldn't it just not work at all?

Okay. Mass determination should still be checked...

Hi,

Power supply voltage was checked again today using a test lamp, and there are no errors.
Weight is also measured without problems.
I have now directly connected the K-line from MSTG to the OBD-connector using a new cable.
Unfortunately, without success. The engine control unit is unresponsive.

Hypothesis: Is the engine control unit (ECU) faulty?

Greetings

The K-Line from MSTG (Pin 61) no longer has a connection to the old line.
(neither on the MSTG side, nor on the diagnostic connector)?
If so, please disconnect (otherwise you may cause a short circuit).