Glow Plug Issues: Intermittent Light on AEL/AAT

Hello,

I experienced a brief malfunction for the first time in my car (230,000 km). The engine 'stuttered,' the preheating indicator lit up briefly (probably for a limp-home mode indicator), but it was only for half a second, and then it was gone.
'And then, on the way back, it happened again, but this time with a complete reset of the control unit?! This meant that the ABS light and other warning lights came on briefly, and I had to reprogram the window lifters and central locking system.'

There were no error entries. However, it's possible that the error was overwritten by the reset during the second occurrence.

I once tried to get in touch with someone at NHG, but I got no response.
Otherwise, I suspect the crankshaft speed sensor.

Does anyone have any other suggestions?

Best regards, Kai.

I've experienced similar issues with the preheating indicator lighting up like this before, and in that case, it was because my relay 109 failed due to a cold solder joint.

Do you also have an AAT or AEL? Where is relay 109 located?

Best regards, Kai.

No, I had an AGR.
Actually, your model wasn't supposed to be affected by cold solder joints.
But I think this can happen with any older Ralais 109.
It is located on the dashboard, underneath the steering wheel cover.

Hi,

My mechanic tapped the speed sensor. He said it was faulty, replaced it. I had 1500 km of trouble-free driving, and then yesterday... oops, it was happening again. A complete reset was needed, including forgetting the window settings and having to re-pair the remote central locking system.

Does anyone have any other suggestions?

Best regards, kai.

kmrlange wrote:

Does anyone have any other suggestions?

Hello Kai,

Please check the grounding connections from the battery to the engine and the chassis.

hi,

Here's a likely solution to the problem:

The search for the 'ground connection' began under the rear seat. (Where else )
There, the connector (on the left side) of the alarm control unit was loose! The retaining clips were broken.
'It's likely that a poor connection or intermittent contact triggered an undefined error in the system, which resulted in a reset of the engine control unit. Since the connector was properly secured, the error has not reappeared.'

Best regards, kai.

hmmm, engine control unit reset, do I need to relearn the window lifters?

I also think, like Bertil, that the problem might be related to a common power supply issue, specifically a grounding problem. Your connector wouldn't explain the issue with your door control module.

Is the error really fixed?

Well, whatever, the error has not occurred again since the mentioned connector was attached. And that's been for quite a few thousand kilometers. I'm sure that's what it was. Maybe a control unit had a breakdown and triggered a complete RESET . However, I am satisfied.

Best regards, Kai.

...

the ultimate realization:
The error only occurred when the rear seats were occupied.
In the event of a malfunction, the weight pressed the metal supports of the rear seat frame onto the positive terminal of the battery. Corresponding signs of electrical current/heat damage are visible on the support.
A brief short circuit directly at the battery has reset all control units.
Therefore, the need to re-register the FH (presumably a system or device) is also understandable.
Okay, so please pay attention: Always make sure that the positive terminal of the battery is insulated and pointing upwards.

Best regards, Kai.

Thank you for the clarification! Isn't a positive electrode cover already planned for that area?

'In any case, if the error occurs, there is a missing cover. Certainly, branded batteries have a cover. It may be broken or improperly attached. I am not familiar with any cover on the vehicle side.'
Best regards, KMR.

Perhaps it would be a good idea to cut a rubber mat to size and place it on top as a preventative measure.

A truly interesting bug! Thank you for the feedback.

You can be glad that the brace wasn't even welded in place.

Do Audi C4 cars really have a common problem where the onboard computer malfunctions, and the metal supports in the seats overheat, causing the upholstery to smell?
I once had one, despite the battery cover (which broke).
The most important thing is to never permanently screw the bench seat in place, so that you can quickly remove it if necessary.
"Attention: We have a problem... quick exit from the back..." and then run around the car .

Yes, it's unbelievable. It seems the electrical development team at Audi didn't communicate with the mechanical design department. Or not enough. Because otherwise, the car is something that brings joy every day. But this strut really hits the positive terminal right in the middle.

One could remove, relocate, or modify the corresponding brace under the rear seat. It's essential to use a material that is strong enough not to break, especially when the mother-in-law is using it .

Best regards, Kai.

P.S. Maybe someone will eventually show some mercy and help me out with my two bodywork threads...