VW Golf manuals

Volkswagen Golf Service & Repair Manual: Trailer detector control unit -J345-

General description:
The trailer detector control unit -J345- detects a power consumption of at least 5 W → Remark when “towing a trailer” and passes this information to various control units via the CAN data bus.
The trailer detector control unit -J345- receives information (regulation of lights) from the onboard supply control unit -J519- and the convenience system central control unit -J393- via the CAN data bus.
1)  The turn signal system or the side lights must be switched on to detect the “trailer”.
Information concerning checking the control unit, fault displays and fault finding is located in the workshop manual → Electrical system; Rep. gr.97.
Retrofitting trailer detector control unit -J345-
Retrofitting a trailer detector control unit -J345- is possible in essence but not easy because it has to be connected to the CAN data bus of the vehicle. The control unit then has to be coded with the aid of “Guided fault finding” → Vehicle diagnostic tester.
It is recommended that alternative control units available on the open market and not approved by Volkswagen are avoided without exception. If equipment of this type is installed, the guarantee will become void. Generally, these are connected to the tail lights and not integrated in the electrical system of the vehicle, which makes far more sense. The consequence is that faulty diagnoses in the bulb failure warning system or malfunctions can occur, among other things. Furthermore, dimmed bulbs (combined brake and tail light) cannot be actuated.
Coding trailer detector control unit -J345-
Coding is described in → Electrical system; Rep. gr.97.
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