Choosing the correct electrical installation for you and your car

When you are towing you will be required to display your rear number plate and a lighting board on the rear of the object being towed. In order to achieve this we use the signals from the vehicle to control the lighting board.

The way in which we wire into your vehicle will vary firstly on the make/model/year & secondly your preference. The four options can be broken down:

1) Standard Hard Wire - Budget option for all vehicles without canbus or multiplex wiring (generally vehicles older than 1995)

2) Canbus bypass relay – Compulsory for vehicles with canbus or multiplex wiring (nearly all manufacturers post 2004)

3) DEDICATED manufacturers approved wiring – Most professional option for vehicles with or without canbus or multiplex wiring. Keeps in line with manufacturers warranty

Skoda Octavia with Dedicated wiring

Fibre optic parking sensors

Ford Transit with Dedicated wiring

Ford Transit Custom

Audi A6 with Dedicated wiring

Audi a6 dedicated wiring

Did you know most DEDICATED wiring options require your vehicles ECU to be programmed/coded to accept the additional trailer module we install as part of your towing package – Automotive Control are able to program this for you saving you a trip to the local dealership!

1) Standard Hard Wire:

Using modern towing sockets with ‘thin wall’ (high current) cabling we connect to your car in the traditional way. We do not use or recommend scotch locks as a permanent method for wiring into vehicle electrics. We will install an audible buzzer giving off an audible warning whilst indicating left/right when towing.

2) Canbus Bypass Relay:

Most vehicles manufactured within the last few years use very sophisticated multiplex or canbus wiring systems.

This type of electrical system can be very complex, the circuits can not be modified because the cable voltages/resistances are monitored constantly by the cars ECU. In order for additional electrics to be added onto your vehicle (eg: towbar electrics) we are forced to use a full Canbus Smart/Bypass relay.

This relay system will ensure no additional load is applied to the car, therefore not causing any damage or malfunction to the vehicles on-board electronic computer (ECU) or bulb failure warning system.

This option will not allow any interactive features like rear PDC cut-off or trailer stability (TSP) that can be found on many modern cars. Please check your handbook for terminology such as: T-ESP, TSP, DSC, VSC.


Common vehicles supporting Canbus/Multiplex wiring systems:

Many cars have carried a level of CAN or Multiplex wiring since the 1990’s but often limited to certain modules within the car and not necessarily relating to the vehicles lighting circuits.

Most VAG from 2003, most GM vehicles from 2003, Citroen 2006 on, BMW 2000 on, Mercedes 2002 on, Saab 2004 on, Volvo 2004 on have fully monitored the exterior bulbs and therefore would require a Bypass Relay to function correctly. We will determine whether your car requires such relays.

3) Dedicated Manufacturers approved electrical kits:

Specifically designed for your vehicle make, model & engine type.
Dedicated electrical kits work in harmony with modern sensitive and complex wiring systems.

Each dedicated vehicle electrical kit will differ, some kits can change the way the vehicle functions whilst towing. They can also range in price from £50 to £250 upwards…and sometimes require the vehicles ECU to be programmed (even if a new car). Automotive Control will program for you.

Dedicated tow bar wiring kits can aid installation of towing electrics. However they are not ‘plug n play’ and still require connections into the vehicles wiring loom or connections to the vehicle CanBus network system.

This type of wiring can often be more time consuming than the installation of standard towbar wiring.

Ford rear PDC cut-off whilst towing

Ford Transit Custom with Dedicated Towbar Loom

BMW iDrive auto PDC cut off

Key Advantages: (vehicle dependent)

  • Manufacturer specifically designed and approved
  • Monitoring of trailer bulbs
  • Dashboard warning and towing symbols
  • Any towing specific towing program the car has will be enabled
  • Hill start assist
  • Crash anticipation
  • Parking sensor cut-out whilst towing (stops constant beeping when hitched & reversing)
  • Rear fog cut-out on car only whilst towing (stops reflection from caravan)
  • Trailer Stability Program (TSP) enabled
  • Suspension adjustments
  • Braking adjustments
  • Traction Control adjustments
  • Aligns with manufacturers warranty & guidelines for installation of additional towbar wiring.

For further information please refer to your manufacturers hand book under ‘towing’ or visit

The Towing Buzzer:

It is crucial to have a bulb monitoring system when towing, our installations will be fitted with a piezo buzzer, this will primarily detect when a trailer is hitched-up to your vehicle, confirmation of this will be a beep/buzz from the buzzer every time the vehicle indicates left, right or when using hazards. If an indicator was to fail the function of the audible buzzer will which is to alert you of a fault.

The buzzer also reminds the driver that they are still towing, the piezo buzzer (installed in the boot) will sound every time the vehicle’s indicators are used when a trailer, caravan etc are being towed. No noise will be emitted once you have disconnected the towing socket.