Engine failed to start.

Hello,
'Because I was having trouble starting my A3 TDI 1.9 engine, I read the error codes with a VAG1551 scanner and received the following message.'
1 error detected.
17978 P1570 035
Engine control unit locked.
intermittent error
sporadic error
occasional error
After clearing the error, the engine started normally as expected.
The problem I'm having is that I can't derive a coherent explanation from the list of causes.

Error code: 17978.
Engine control unit locked.

Possible causes:
Attempt to start with an unauthorized key. (I have tried all available keys without success).
Attempted manipulation (This seems unlikely; there are no signs of manipulation to be found).
Short circuit in the communication line (This would have to be a loose connection that is resolved at the very moment the error is cleared, and has not occurred again since, which I also consider unlikely).
incorrect encoding (What can cause the encoding to be incorrect if the car was parked normally?)
Errors in the anti-theft system (What causes errors in the anti-theft system?)

Immobilizer control unit defective/missing (This shouldn't be the case, as everything is working normally right now).
Engine control unit replaced, but not adjusted to the immobilizer. (Nothing was replaced; everything was as it was after the last trip.)
During the unsuccessful start attempts, there were no instances of ignition; the engine didn't even start briefly, it simply didn't ignite at all.
All the necessary conditions for the jump to occur were present.

Has anyone else experienced this problem before? I would appreciate it if someone knew something about a possible cause.

Best regards, Peter.

Perhaps your key accidentally fell and somehow damaged the transponder?

Just a sunny idea.

Arne.

Hello Peter,
It sounds like the relay that supplies power to the control unit.
- No engine noise.
- nonsensical error messages

Perhaps one of the A3 drivers (Rainer) can tell you exactly where the relay is located and how it is labeled.

Hello,

Since only one error was saved, it's highly unlikely that the relay is broken (usually, that would result in around 8 error entries).

What kind of engine and transmission does it have? Please provide the text you would like me to translate from German to English. I will then provide the translation. After that, if you provide the motor and instrument cluster codes, I can include them in the translation.

Hello Peter,

The relay is marked with the number 109 and is located in the relay panel, which is easily accessible on the driver's side after removing the lower dashboard trim.
When a relay is defective, you can crank the engine as much as you want, but it simply won't start.
However, the final failure of my relay had been foreshadowed for a long time, with intermittent issues during operation that ranged from fractions of a second to 30 minutes.
According to the workshop, there were all sorts of nonsensical error messages stored in the system's memory at the time. Michael can tell you more about this (I don't remember exactly what the errors were or how many there were, as I didn't have a diagnostic system back then).

Best regards, Rainer.

Hello Arne, Rudi, Michael II,
Thank you for the quick response. Yes, I also immediately thought of Arne and the transponder, and I tried my spare keys without success. Rudi, I don't know anything about the relay, but shouldn't there be an error message?
Now I finally have hope that the truth will come to light. Michaell II, I have just read out the latest codes.

8l0919860 VDO instrument cluster, combination instrument, part number D07, coding 00040, WSC 69795.

03890601A 1.91 R4 EDC GOOAG 1001 Coding 00001 WSC 69795 Engine Control Unit.
Engine EGR.

01M927733FF AG4 Transmission 01M 3393 Coding 00000 WSC00000
Automatic transmission.

Interestingly, during the initial error reading, the central locking pump displayed an error message, and errors were reported for an alarm system, even though no alarm system is actually installed.

8L0862257E Power steering pump, coding 00000, WSC 65535.
8 errors detected.
No. 01367, 01371, 01372, 01374, 01370, 01369, 01368, 01373.

I'm glad I found this forum, and I admire your expertise.

Best regards,
Peter.

Hello,

The coding for the engine, transmission, and instrument cluster is OK.

"Only the coding for the central locking system (just the central locking, without the alarm system or remote control, etc.) and the error messages seem strange to me."

You don't have a remote control for your home automation system, do you? What is the model year of your car?

Hello Michael II,
Year of manufacture: 1997, no remote control.
Yes, it's all quite strange, and I can't explain how the error message appears when the DWA (digital water meter) is not present.
I hope you can find a logical explanation.
Best regards,
Peter.

Hello,

The aforementioned errors can also be triggered by what is quoted as "misoperation of the central ventilation system," where the mass remains active for longer than 1 minute. Does anything come to mind regarding this? Did you, for example, hold the lock for a very long time?

Hello Michael II,
I can't quite remember, but on one of the hot days, I lowered the side windows, and to do that, you have to hold the key in the ignition longer than it takes to unlock the door.
If this leads to such an error, then it should be reproducible by repeating the action and holding it for a little longer.
The problem is that there might be situations where a reading device isn't available.
I've also heard that there's supposed to be an emergency function that can be activated on the combined device.
I am very grateful that you found a plausible explanation, and I hope it helps others as well.
Tomorrow, I will try to reproduce the error and then report back.
For now, thank you very much.
Bye Peter.

Hello Michael II,
This morning, I tried to reproduce the error, but unfortunately, I was not successful.
I don't think that's likely at the moment, because holding the key in the 'on' position for a full minute is a very long time, especially considering that the windows only take about 10 seconds to move to a different position.
It would have been nice if the error could be explained by that, but now I have doubts that this was the cause of the error.
Do you have any other ideas?
Best regards,
Peter.

Hello,

It's also possible that a cable has an intermittent ground connection. If the vehicle is locked, you wouldn't even notice.

Hello Michael II,
That would suggest that there's a loose connection or a faulty cable insulation somewhere in the vicinity of the castle or castles.
Do you have any idea which area I should be looking in, or could it be anywhere in the entire wiring harness?
Regarding the emergency activation using the combination instrument, can you tell me something about it?
Damn, when you have to deal with 'occasional' errors.
I would like to say thank you again to you and everyone who offers help here.
Best regards,
Peter.

Hello,

You will need the four-digit security code located on the keychain.

- Turn on the ignition.
- Simultaneously, pull the setting knob for the clock and press the reset button for the trip odometer.
- The display should now show "0 0 0 0". The first dot is blinking.
- Press the "back" button repeatedly until the first digit matches the secret number.
- Pull out the setting knob on the clock and enter the next setting.
- Has the last digit also been entered? If so, simultaneously pull the setting knob for the clock and press the reset button for the trip odometer.
- The indicator light for the parking/leaving home function must now be illuminated.
- Turn off the ignition.

The engine should now be able to be restarted.

Hello Michael II,
Hopefully, it will work if there's no other option.
To do a dry run and see what happens when things go completely wrong, what adjustments do I need to make to simulate a complete system failure?
At home, it's not a risk because I can use the 1551 to clear the error again.
I have two more questions: Where can I find information about VAG-com? I believe that this system can replace the 1551, and if so, does it offer all the same functions as the 1551?
I also have some questions about my automatic transmission, but that's a very extensive topic and not so urgent. I've already come to terms with the minor flaws, and I now assume that I have to live with them.
Best regards,
Peter.

Hello,

Simply hold the lock button for longer than one minute.
Regarding VAG-Com: The current version has a significantly larger scope than the 1551. The homepage for this is: Ross-Tech.