BKD is failing, no glow plug activity when ignition is on

Hello everyone,

I'm having a problem with my 2.0 BKD engine.
The engine occasionally stalls while driving, specifically when releasing the clutch.
Starting attempts were unsuccessful; the starter motor turns, but the engine doesn't start.
Error description:
- The indicator light for the heating element does not turn on when the device is switched on.
- electrical Power steering pump running constantly.
- After a longer period of cranking, the preheating indicator light starts to blink.

Error memory:
- No communication with the engine control unit.
- and almost all of them occasionally malfunction.

Tested and swapped.
In this condition, the engine control unit (ECU) does not receive power.
Relay 458 is therefore not engaging.
All work relays have been replaced.
"The glow relay/glow plug control unit was replaced... since then, there were no errors for about 3 months... unfortunately, the same error code has reappeared today."

Can someone help me?

Best regards,
Manfred.

Audi_S-Power wrote:

The glow relay/glow control unit has been replaced... since then, about 3 months without any errors... unfortunately, today the same error code appeared again

. I would start by checking the connectors/wiring harness thoroughly. Most likely, the old STG (steuergerät) wasn't actually defective, but the connector or a cable had a loose connection, which is why it worked again after the replacement.

How is the power supply for the vehicle's electrical system realized by the engine control unit (ECU)? Cold solder joint, similar to the ones found in the "109" relays commonly used in Volkswagen Golf 4 / Audi A3 8L models?

Best regards, Rainer.