I bought my TD6 L322 to use as a tow tug for a 3T trailer and found the trailer wiring somewhat difficult. So here is the result of my efforts to do it properly -

The L322 Brake lights are all LEDs, this is a backup for failed indicators (pulse them slow at 0.5s), tail lights (pulse them fast at 30%) or rear fogs (pulse them fast at 70%). The Brake pedal switch is a Hall Effect magnetically controlled transistor with just a tiny trickle of power through it.
The L322 Light Control Module (LCM) uses special 'load reporting transistors' to switch lights on and off. While 'OFF' a short pulse is sent to every light every few seconds and the load report evaluated for failure or overload (Cold Testing). While 'ON' the load report is continuously evaluated for failure or overload (Hot Testing). Once a failure is found it is reported and the transistor is only switched on for further Cold Testing until a successful test occurs (no need for fuses).

All the above means trailer wiring also has to have special circuitry to handle the pulses and power levels. Hence the Trailer Control Module (TCM) that takes Tail and Indicator signals from the LCM, the Brake signal from a dedicated wire and the Trailer Rear Fog and Trailer Reversing Light signals via a dedicated data bus. The TCM also uses load reporting transistors to test the trailer Tail and Turn globes and reports back to the LCM via the dedicated data line. LED trailer lights fail the globe tests so the vehicle's rear sonar, reverse and fog lamps never get dissabled and the trailer's reverse and fog lamps never get enabled.

So the first thing you need is a suitable wire loom starting from connector C0380 that hooks a Siemens TCM into connector C2586.
TCM part numbers - BMW 61.35-6 908 767 or newer BMW 61.35-6 955 253 or older BMW 61.35-8 369 019

Connector C2586 is in place in the rear fuse box of every L322 (2002-2005) just waiting for the trailer wiring kit to be added. Note - all early models exported to Australia have the TCM and a British 7 pin socket already fitted, most reputable dealers swapped in an Australian socket, but not all. Later, when Ford was swapping in their parts, its became a bit hit-and-miss. Also note that the TCM for the US market is different to the unit used for the rest of the world.

Click image to enlarge

The TCM has 5 direct inputs from the LCM. Four are in parallel with the L322 rear lights - Left Tail, Left Indicator, Right Tail & Right Indicator; the Cold Test pulses on these are simply ignored by the TCM. The Brake input though is a dedicated line with only ON/OFF, no test pulses or 30% or 70% or 100% operating pulses. As the L322 Rear Fog and Reversing lights are disabled when a trailer is detected the TCM gets switch data for these functions through the I-Bus.



The numbers in the diagram are connector#-pin# eg 0380-9 is connector C0380 pin number 9.

The TCM has 7 outputs which are combined with 2 power lines and 2 grounds to make up 11 of the 13 cables used in European Trailer Sockets. Unfortunately only some of the cables are 'universal' colours, so some alterations need to be made when other sockets are used in different countries around the world.

Electric Brake Controllers always use the American Colours of Black = Hot Wire (+12V), White = Return Wire (0V), Red = Brakes ON input and Blue = Operate Brakes output. I mounted my controller just below the diagnostic socket on the driver's side dash fascia.

The ONLY safe place to source a 'Brakes-Are-On' signal is the Black/Blue cable from the LCM C0937 pin 10 to the TCM C0380 pin 9. Older Brake Controllers WILL work with the Brake Lights output from the TCM, but modern, computerized controllers MAY have a problem with the 'Cold Test' signals. Best to use the 'proper' signal.

The LCM is in the 'A' pillar, beneath the dash board on the right hand side. You can source all the inputs for a Brake Controller from there - The middle connector C2039-pin 8 is +12V and C2039-pin 2 is Ground; the Black connector C0937-pin 10 is 'Brake is ON'. The output from the Brake controller then has to be run to the rear fuse box to connect into the trailer loom.

You can source it all at the LCM, but it is much, much easier to get it from the TCM and run a 4 wire cable to/from the Brake Controller. The TCM is in the rear fuse box. Its only connector C0380 has +12V at pin 8, Ground at pin 15, 'Brake is ON' at pin 9 and the Blue wire to the loom is at pin 3. Just cut the Blue wire (unused Rear Fog light) about 50mm from the connector and splice the Blue wire from the Brake Controller in.

Click image to enlarge

* Since 1988 Australia has had only one regulation for light vehicle to trailer connections which specifies just 4 types of connector; all of which have the lighting functions assigned to the same pin numbers.
A type 1 socket is round containing 7 pins numbered clockwise from the top, 6 on a diameter of 20mm + #7 in the centre. There is an alignment notch at the bottom, pins 1, 3, 4 & 6 are male and pins 2, 5 & 7 are female. The smaller type 2 socket is round with 7 female pins numbered anticlockwise from the alignment notch at the bottom, 6 on a diameter of 13mm + #7 in the centre. Type 3 sockets are rectangular and can be a single row of 7 small female pins or have a second row with 5 larger pins. Single row plugs will fit into double row sockets. Ground pins are in the middle of each row with the lighting ground offset for alignment purposes. The first row of type 3 sockets appear to be numbered randomly, but in fact mirrors the curved groupings of Type 1 sockets.

* Electrically operated service brakes are mandatory for trailers over 2T in Australia. The control unit has to be positioned where the driver can operate it manually in an emergency. The unit must be powered directly from the tow vehicle battery to facilitate operation at all times. When a signal (from a brake light or the tow vehicle's computers) is present the rate of deceleration is monitored by the unit and the trailer service brakes voltage output is adjusted to slow and stop the combined tow vehicle/trailer in a controlled manner.

* Breakaway automatic brake applicators are also mandatory for trailers over 2T in Australia. These 'units' consist of a battery charger/monitor, a small dedicated battery and a tethered pull-pin switch to apply power to the trailer's electric brakes in the event of a coupling failure. For safety reasons Breakaway chargers MUST be connected through the normal trailer plug (not some extra plug that may be forgotten, or is not fitted). In Australia this will be supplied through pin 8 & in Europe pin 9, NOT the same pins as any high current demand (eg a refrigerator in the trailer). Additionally some legislations require a monitoring signal from the Breakaway battery for the driver. In NSW, Australia the monitor signal could be on pin 11, but usually is on pin 12. (Some older 7 pin plugs incorrectly supply +12V on pin2).

* Electronic Stability Control (ESC) may need to be disconnected when travelling over rough ground, so it is common to power these via 'Anderson Plug' connectors rather than the normal trailer plug. Red Anderson Plugs are typically used in this situation, connected directly from the tow vehicle's starting battery/alternator. Alternatively wire in parallel with Breakaway from AU pins 8 & 10 or UK pins 9 & 13 if disconnection is not envisioned.

* To operate a 12V absorption refrigerator in a trailer whilst towing, a high power cable and a switching system should be used (many newer fridges have a built-in Voltage Controlled Switch (VCS) or trigger operated via a 'D+' terminal). In Australia D+ is from pin 12 with power from pin 9 or a grey Anderson plug. In EU D+ AND power is from pin 10. Just use the power pins when using an external VCS.

* For charging House Batteries in a trailer 'on the move' a high current connection via an 'Anderson Plug' is often used in conjunction with a voltage sensitive relay (in the trailer) but this often doesn't fully charge the House Batteries. This is due to the voltage losses in the long cables, the amount of extra power available from the alternator, the 'smart' control in newer vehicles and the relatively short duration of the travel.
Common practice is to use a cheap grey Anderson plug for the house battery charge circuit. Alternatively wire in parallel with refrigerator from AU pins 9, 10 & 12 or UK pins 10 & 11 if current demand is low enough.

* 50A Anderson plugs, especially clones, are cheap, reliable and basically idiod proof. Different colours prevent confusion as only same colour Anderson plugs will mate. A voltage controlled switch or a DC-to-DC converter with input cut-off set higher than the starting battery's 'floating' level (12.6V) needs some form of identification which these plugs can supply - a Red plug almost always implies a direct-from-battery connection while Grey or Yellow, etc plugs indicate some control device is attached. Another advantage is that a red plug provides an easily accessible external connection point for a mains or external solar charger, direct into a tow vehicle or into a trailer.

* Rear view cameras should be wired via dedicated 4 pin connectors to ensure proper shielding over the long run from the rear of the trailer to the tow vehicle's dashboard. The Reverse Camera wiring scheme shown here is according to 'Waza' cable pin usage where +12V = pin 1, (shared) Ground = pin2, Audio = pin 3 & Video = pin 4. The plugs and sockets are Universal Aviation Connectors, 12mm Thread diameter, Type GX12, 4Pin (available on ebay at $10 for 10 x line plugs + 10 x chassis sockets). While male line plugs are readily available, female line sockets are almost impossible to buy, but can easily be fabricated from a chassis socket, a 20mm length of 12mm poly pipe and some silicon sealant. Cable is cheap S-Video type.

* And now for the L322 Gotcha. The Engine Management Computer measures current load over the ground lead between the starting battery and the chassis along with voltage at the positive battery terminal in order to better manage charging of the starter battery. If a second battery is in parallel with the starting battery (even if it is behind a Voltage Controlled Switch) the EMC will become confused and will not charge either battery properly resulting in (dramatically) shortened battery life. The early model L322 (2002-2005) can avoid this by connecting all extra ground leads to the chassis (never to the starting battery's ground terminal). But later models have Euro 5 level battery management and require complete isolation of extra batteries via Direct Current to Direct Current step up/down Chargers. VCS is Ok for before 2006, but later models must use DC-DC Chargers instead.


This is what I did -

Hi. Just found this post. I have LED lights on my caravan and the brake lights flash on and off. I found another post where the black/blue wire is connected to the red wire to stop this happening. Is this what you have done above?

Hmm, I thought Oz delivered L322 came prefitted with a towbar and wiring (according to a mechanic friend who worked at a dealer) Ron B. VK2OTC
2003 L322 V8 Auto
2007 Yamaha XJR1300
Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA

The pre-fitted wiring assumes old style globes on the trailer and only has a 7 pin plug with fog lights wired to pin 5.

You really need to snip the fog light connection, and if using electric brakes on the trailer then the brake 'ON' must come from the dedicated output on the light control unit (not the pulsed signal to the LED Brake lights) and the output goes to pin 5.

bye. 2003 TD6, EGR delete, vortex crankcase breather update, performance chip, UHF 2 way, Android head unit, crash camera on dash, always-on rear view camera to mirror screen, LED DRL`s, Electric trailer brake controller. FSR replaced. Pulling 3T caravan all about Australia

I don’t think you have 13 pin plugs in Australia so the wiring is going to be different to the plug.

Australia doesn't use 13 pin EU style, nor UK N & S types, nor US opposed flat pins, we've got our own! arr, nearly.

There are a multitude of plug types still in use here, containing from 3 to 12 pins. But there are only 2 being fitted to new, private use trailers.

They are a round 7 pin (13mm pitch circle) and a rectangular, single row 7 pin derived by 'unrolling' the round pin pattern. But wait, there's more ---
The small pins in these are rated at about 8 Amps each (but are usually nearer only 5A due to dirty / loose contacts, etc). So for more power the round plug comes in a bigger version, 7 x 20A pins on a 20mm pitch circle. And for more circuits (with more power) the rectangular plug gets a second row of 5 x bigger pins (total = 12 pins).

The preferred installation is the rectangular 12 pin socket on the tow vehicle which accepts either a single row 7 pin or a double row 12 pin plug from trailers. This is often supplemented with 1 or 2 x 50A Anderson plugs for running fridges or charging auxillary batteries. This is what I installed as described in an earlier post.


bye. 2003 TD6, EGR delete, vortex crankcase breather update, performance chip, UHF 2 way, Android head unit, crash camera on dash, always-on rear view camera to mirror screen, LED DRL`s, Electric trailer brake controller. FSR replaced. Pulling 3T caravan all about Australia

Hmm, a lot of reading to do here! My L322 came with the factory fitted towbar and wiring. What was supplied in Oz was the towball mount as it's different to the UK style.

I've just bought a secondhand trailer and replaced all the dodgy wiring and replaced the incandescent lighting with LEDs. I have one of Lee Bourgeios' (Labtronx) pulse busters so I don't get flashing LEDs when it's in circuit.

However, what doesn't work are the trailer reversing lights. I'd like them to work.

The workshop manual says:

Quote:

The rear fog lamps and reverse lamps are not directly connected to the lamps units because these lamps must be disabled when the trailer socket is connected.

I would guess that it means that the car lights will not work as it says when the trailer socket is connected. Also you would not need the reversing and fog lights work on the car,only on the trailer. 2011 4.4 tdv8 Kahn. 2007 supercharged with 2012 lights and overfinch body kit. P38 with a full J.E.Engineering conversion

I thought the same so, after reading the workshop manual, I tried it but both the reversing lights and rear fogs still work.

I guess I need another L322 owner who has a caravan to check his for me. Ron B. VK2OTC
2003 L322 V8 Auto
2007 Yamaha XJR1300
Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA

At least the reverse light problem is solved.

The Oz delivered L322 only came with the black 7-pin plug so the reverse light isn't brought out to the trailer connector. The UK 7-pin plug uses pin 2 for rear fogs. In Australia, pin 2 is for reversing lights.

If I turn on the L322 rear fogs, the trailer reversing lights come on. I shall have to delve into the wiring in the wheel well to move a wire or two. I don't have rear foglights on the trailer. In fact, I don't think I've ever used the fog lights in this or my previous two or three Rangies - we simply rarely ever have fog. On my RRC, I wired the rear fogs through a relay such that they were normally a set of extra stop lights. If needed for fog, they could still be switched in. Ron B. VK2OTC
2003 L322 V8 Auto
2007 Yamaha XJR1300
Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA

On my RRC, I wired the rear fogs through a relay such that they were normally a set of extra stop lights. If needed for fog, they could still be switched in.
I fitted diodes between the stop lights and fog lights to achieve the same results on my RRC.

At the time I didn't have any diodes bigger than 1 amp.  Ron B. VK2OTC
2003 L322 V8 Auto
2007 Yamaha XJR1300
Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA