VW Tiguan AD1: P0684 Error Code Explained

Hi there,

I already opened this topic yesterday and also uploaded the requested Autoscan file.
Unfortunately, it was deleted, so here it is again:

Problem description:

4976 - Glow plug control unit 1 (J179)
P0684 00 [237] - implausible signal.
Warning light ON - confirmed - checked since last reset.
Environmental conditions:
Error status: 00000001
Error priority: 2
Error frequency: 1
Mileage: 169463 km
Date: 2023.03.06
Time: 18:48:37

Motor speed: 0.00 rpm.
Normalized load value: 0.0%
Vehicle speed: 0 km/h
Coolant temperature: 14 °C
Intake air temperature: 18 °C
Atmospheric pressure: 990 millibars.
Voltage at terminal 30: 11.860 V.
Lost learning counter via OBD: 40.
Electric auxiliary heater: Shutdown conditions - bits 0-7: 0.
Electric auxiliary heater: Shutdown conditions - bits 0-7: 0.
Electric auxiliary heater: Relay control bits 0-7: 0.
Preheating time: 1200 ms.
Indicator status bits 0-7: 0.
Glow status bits 0-7: 80
Glow cycles above the temperature threshold bits 0-7: 0.
Glow cycles above the temperature threshold bits 0-7: 2.
Glow cycles below the temperature threshold - bits 0-7: 0.
Glow cycles below the temperature threshold - bits 0-7: 0.
Outdoor Temperature Sensor 1, Bank 1: Raw Value: 4.0 °C


Readiness: 1 1 0 0 0


The engine was also difficult to start, but then it ran normally without any problems. I then removed the glow plug control unit.
Part number 04L 907 282 B, Type 527.
From the outside, it seems inconspicuous, but unfortunately, it's ruined/spilled.
I tested the four glow plugs, and they all measure between 1.4 and 1.5 ohms.

My questions were:
Which fuse is responsible for the glow plug control unit?
If it needs to be replaced, is a replacement part from Volkswagen the best option, or are there experiences with replacement parts from Bosch or Hella?

Best regards from the far north.

Faxes.

Hello,

Testing glow plugs with a multimeter and the typical low current of just a few milliamperes (if any) is neither useful nor informative.

See:
Replace the spark plug or alternatively,
Check glow plugs, Glow plug check.

Background information spark plugs.

Spark plug fuse: See Erwin (a parts catalog), possibly a ceramic fuse with screw terminals near the battery.

Best regards, Rainer.

Always remove the glow plugs, energize them, and check if they are functioning as required.

Good evening, Faxe.

the glow plug control units with the part number...

04L 907 282 B are defective.

The following applies to all control units with index B.

a hardware version smaller than 12.

and

a software version less than 14.

See TPI 2050455/7.


You should also keep an eye on the low voltage issues in various control units. Either your AGM battery is failing, or you have a grounding problem.


Best regards,

Michael.

Hi Michael,

Thanks for the information, does that mean mine is included too?
I'm attaching a photo.

Does TPI have any comment on whether VW will replace it?
I guess not after 5 years?

Would you get the part from VW, or would you consider using a brand like Bosch or Hella instead?

Best regards from the far north.

Faxes.

Hello Faxe,

Generally speaking, repairs can be billed through the warranty program (TPI). However, only your authorized dealer workshop can tell you whether this applies to your specific vehicle.


The original VW part costs around €100 plus VAT.

Personally, I would choose an OE (Original Equipment) control unit.


Best regards,

Michael.