Motor-SG locked

Hello!
I've been having a problem with my car (A4 TDI PD quattro, manufactured in 2000, engine code: ATJ) for the past 2-3 weeks, and it's like this:
The car won't start in the morning when I try to start it for the first time; it starts briefly and then immediately dies. On the second attempt, I have to keep the ignition on for a longer period (15-20 seconds) before it starts. After that, it starts without any problems throughout the day. The next day, the same thing happens again, and so on...
I had the error codes read, and this is what came up:
System: Motor
Error text: 17978
DEPARTURE RESTRICTION.
MOTOR-SG BLOCKED.
ADDITIONAL INFO: Intermittent error.
INFO:
The motor control unit (Motor-SG) does not receive the "release" signal from the departure control unit (Wefahr-SG) upon request. The departure control unit can be integrated separately, in the switchboard control unit (Schalttafel-Einsatz-SG), or in the motor control unit.
Bitte gib mir den deutschen Text, den du übersetzt haben möchtest.
CAUSE:
- Interruption/Short circuit/Resistance in the electrical circuit.
- No power supply / Faulty power supply.
-Incorrect unlock code.
-Encoding error; please re-encode if possible.
- Interference caused by high-voltage power lines, telephones, audio systems, etc.
-Faulty control unit.


Does anyone have any ideas what might be causing this?
I would be grateful for any help.
Best regards, Marcel.

It would be interesting to see what's stored in the error memory of the combination instrument (25), because that is the...
The other half of this process (including key verification).

Best regards, Micha.

Error found... the temperature sensor was at fault.

marco_A4_avant wrote:

Fehler gefunden....war der Temperaturgeber schuld...

How did the temperature sensor manage to do that?

I had to take the car to the workshop yesterday because the coolant level was too low. Then they saw that water was dripping where the temperature sensor is located. I'm not sure, but this morning the car started on the first try. I suspect that the four-pin connectors were oxidized.
Best regards,

Fehler gefunden....war der Temperaturgeber schuld...
wie hat der Temperaturgeber das hinbekommen?


Not at all .

Exactly my fear.

... the a4 b5 has the annoying problem that the reading head of the windshield wiper system sometimes lifts up, or functions sporadically and is dependent on ambient temperature. This could also explain why it only happened in the morning, and not throughout the entire day (because there's still some residual heat in the car). Just a guess...

Okay... they were right, the temperature sensor wasn't the problem (the initial start-up was a one-time occurrence; after that, it went back to being the same).
I also replaced other parts (air filter, 4 new glow plugs, all hoses), and I tested with a new mass airflow sensor (MAF) and pressure sensor -> it didn't help, no improvement (The WFS error was resolved and hasn't reappeared since + the pre-glow system is also OK).
now I have a new statement about the : the fuel pump is supposed to be leaking (which somehow makes sense, because after longer periods of inactivity, the pump needs more time to build up pressure again, right?).



Best regards,
Marcel.

Okay, I'll put it simply:

If the problem is related to the immobilizer system, as can sometimes happen with the 8D models, such as a faulty wiring harness connecting the transponder coil to the immobilizer or a defective transponder coil itself, then removing and rebuilding the entire engine will not solve the issue; the problem will persist.

If the engine starts in the morning and then immediately shuts off, and the WFS symbol also flashes, then the problem is not related to the fuel pump or anything else like that.

However, the wfs cannot be to blame for 'bad' sound quality, which refers to prolonged or unpleasant organ sounds.

Ultimately, it's up to you to decide what to make of it.

Does it start and then shut off, or does it not start at all?

Hello!
Okay, the WFS light is no longer flashing since I fixed the issue. However, the car won't start unless it has been sitting for a longer period (e.g., overnight). I've noticed that this doesn't seem to be temperature-dependent. If I try to start the car in the morning, I have to crank it for 10-15 seconds before it starts. If I turn the engine off and immediately on again, it starts without any problems, even if it sits for 2-3 hours afterward. But after a standstill of 9-10 hours, I have to crank it again.
The fuel pump has already been ordered; I'll keep you updated on the progress.
Best regards,
Marcel.

Hello!
Yesterday, I had the fuel pump replaced, and this morning, the car started .
Let's see if this was just a one-time thing!
Thank you for your answers!

Okay... that's it! The car starts without any problems!
Thank you for your help!



Best regards, Marcel.