Retrofitting a tow hitch on a Passat 3C, model year 2007 (Solution)

Hello,

A tow hitch from Westfalia, along with an electrical kit from Jaeger, was retrofitted to a VW Passat Type 3C, manufactured in 2007, with a 2.0 TDI engine.

The following error has been detected in the parking brake control unit:

02844 - Lamp for automatic parking function.
009 - Short circuit to ground / Warning light illuminated.

The control unit for the parking brake and ESP is correctly coded, and the trailer function is enabled.

The error cannot be deleted, and the light is on.

It would be great if someone could help me.

"Thank you."

Does the vehicle have parking sensors combined with a parking assist system?

No, no parking assist.

Quote:

The control unit for the parking brake and ESP is correctly coded.

Perhaps it wasn't encoded correctly after all? VAG part number and coding, before/after?

Best regards, Rainer.

Hello, sorry for the delay.

ESP:
Part number 3C0 614 109.
Encoding 0029986, previously 0013602 (+16384).

Parking brake:
Part number 3C0 907 801E.
Encoding 0000012

Best regards,
Matthias

I've now narrowed down the source of the error.
It only occurs when the black/red cable is connected to pin 2 of connector E on the body control module located in the driver's footwell on the left side.

This is the signal from the brake light switch. This is also where you should connect the cable from the supplied wiring harness. The other lights are connected via the CAN bus. There is a voltage of 0.5V on this cable when the ignition is on (idle state). When the brake is applied, there are 12V present.

Even when measured with a multimeter, the warning light illuminates.

After that, you need to wait for about 2 minutes and turn the ignition on and off three times before the error can be cleared.

Is there another way to connect to the brake light switch? Where is it actually located on the Passat? There's no switch visible at the bottom of the brake pedal; could it be a microswitch?

The Jaeger control unit simply applies voltage to the corresponding connector in the trailer socket when the brake pedal is pressed (receiving the signal from the brake light switch, not from the CAN bus).

Should the signal be tapped from the taillight?

Best regards and thank you in advance, DOKA.

Sure, here's the translation:

"Again:"

After approximately 15 minutes of running, the engine shuts off. When restarting, the warning light illuminates again, even though the cable is not connected!

DOKA wrote:

... The control unit for the parking brake and ESP is correctly coded, and the trailer function is enabled. ...

Was ist passiert mit dem vehicle's wiring harness control unit (ECU) in relation to the trailer hitch?
He also wants to know whether or not an auxiliary heating system is installed.


Vehicle network; Control unit coding.

Select STG 09 (Onboard network).
STG Lange Encoding -> Function 07
...
Byte 04 Bit 2: Attachment device installed.

The BNSG does not need to be encoded.

vagtuning wrote:

The BNSG does not need to be encoded.

"With Jäger taillights, it's normal for the brake light function to work even if there are no diagnostic errors. This is because they don't obtain the brake light signal from the diagnostic-capable CAN bus, but rather from an external source." This increased consumption in the brake lights must be reported to the BNSTG.
The original VW retrofit kits, on the other hand, are diagnostic-capable and communicate their "requests and problems" to the vehicle. No encoding is necessary.

VW's BNSG units ignore this byte; only Audi's utilize it.

Furthermore, VW's documentation explicitly states that the Federal Supreme Court also...
is not coded when the AHK (acute hematoma of the kidney) is not diagnosable.

VW also installs systems that are not diagnostic-capable from the factory (see Touran and Caddy), and also frequently installs them retroactively.

Some BNSG codes are now being rejected and withdrawn.
Initially, it wasn't included (starting with a specific software version), which is quite sensible.

vagtuning wrote:

... Furthermore, VW's documentation explicitly states that the Federal Supreme Court also... is not coded when the AHK (acute hematoma of the kidney) is not diagnosable. ...

I am familiar with everything.
And yet, I had already encountered the error. It only resolved after the (unnecessary) encoding step. Even VW couldn't (or wouldn't) explain it.

I will recode the BNSG module for testing. Otherwise, Jäger will send another control unit as a replacement.

It will probably be sometime in the middle of next week.

Thank you very much.

Hello!

Recoding of BNSG - no change.

Jäger sent a different control unit for the electric kit, which intercepts the brake light signal from the CAN bus. I disconnected the cable for the brake light signal from the BNSG (Brake Light Switch).
Now, the error no longer occurs.

Thank you very much, best regards.

DOKA

Thank you for the feedback!