There won't be a signal from the tuner as such, it just picks up the CAN and possibly the infotainment on signal from those connections, check you are getting the CAN voltage at the step module, around 2.5v & - 2.5v measured to ground. I assume the infotainment works as expected? As well as the heavy 'power' feed, I'd expect there to be a 12v control supply as well, can you identify how many wires there are going in to the module? As in inputs, not outputs to the step motors.

Thanks Phoenix.

There is a heavy red and black going into the plug, then there’s the twisted pair for the CAN.

There’s an additional black that goes to the earth point, along with a yellow, orange and blue.

In total, 2 heavy cables and 6 smaller ones.

Update.

Just been to check the CAN voltages.

Definitely getting between 2.2v and 2.3v between both of the CAN wires and Ground at the side step ECU.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

Thinking logically, the three unknown (red, orange & blue) function wires should be a +12V permanent supply for the electronics - possibly the orange, an illumination +ve for the switch backlighting level, possibly red, and a switched +ve to signal power up/power down, I'm guessing blue, purely on the basis that it will be coming from the infotainment relay output. If I'm right, then (ignoring the illumination input which can be checked for quite easily) for anything to work, the other two should be at battery voltage, one permanently - possibly/probably fed from fuse 49 of the CJB with the switched supply fed from fuse 10 or 11 in the rear junction box. All of the above is clearly pure guesswork, based upon nothing other than what's available at the AHU and how I think it should work.

If you're planning on 'injecting' some volts, do it via a 5A fuse...

Thanks Phoenix

I did a bit more digging before it got freezing cold outside.

Input Plug

Heavy Red - Fusebox
Heavy Black - Ground Point in Footwell
Twisted Pair - CAN High & Lo
Thin Black - Roof Switch
Thin Blue - Possibly Roof Switch - No continuity
Orange - Not sure

Roof Switch

Thin Black - ECU Input Plug
Thin Black - Not sure
Thin Blue - Possibly ECU Input Plug - No Continuity though.
Thin Green - Not Sure
Thin Grey with red stripe - Audio Unit Plug

The roof switch still illuminates when the car headlights are switched on but pressing and holding it to enable/disable the steps does nothing at all.

I’m almost at the point where I’m thinking of removing the entire wiring loom and pinning it out on the kitchen table in the warmth.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

I've just re-read the earlier posts - your comment about being above the heater vent may 'have legs', not in terms of damaging the control module but in terms of relaxing the pin grip in the connector housing...
Given the overlay harness doesn't appear to use the same wiring colour scheme, (black rather than brown for ground as an example) when it's lighter & warmer, could you look at the harness that connects to the plug that should go into the radio receiver (or AHU as I called it earlier) and see what colour wires they transition to on the vehicle side? that will give us a much better idea of their function.

There will / should be at least a permanent 12V supply to the control module, it's not standard or good practice to power a control module from the heavy current supply it's switching - not least because of switching spikes. The lack of continuity on the blue needs investigation - does it only appear at the switch and control module input connectors?

The thin grey/red is likely the background illumination supply - easily checked.

I've dug around and sent a couple of emails, no-one as yet has come back with a wiring diagram which is most frustrating!

Been back out and have a look at this again this evening. Here’s what I’ve managed to trace tonight.



The step loom comes out of the AHU but changes colour in the loom somewhere before it reached the step ECU.

I’ve account for all of the pins on the step ECU.

Big Red - 12v feed from fusebox.
Big Black - GND to earth point by bonnet release.
Little Black - Roof Switch - Commoned with Big black (Earth) through the ECU.

Orange - Nothing when checking for power.
Blue - Nothing when checking for power.

Yellow + Brown Stripe - CAN
Yellow + Green Stripe - CAN.

So other than the main 12v feed from the fusebox I’m not seeing anything supplying power to the ECU. I’m reluctant to start giving it a 12v feed as I don’t want to knacker an ECU. The ones that have me confused are the Orange and Blue on the ECU in as I don’t know where they’re coming from. They don’t appear in the feed from the AHU so they obviously come from one of the splices in the loom somewhere.

If there is indeed a small feed that’s meant to feed the ECU then that would explain it not working.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

That helps a lot - there is a Red/Green on pin 11 that is a battery supply, same connector as CAN, this should be live all the time, probably the electronics supply that is missing. I'll try & track down the White, Grey/Red & Red/Blue

ETA
Grey/Red (actually 'slate')/Red {SR} is pin 17, and designated illumination
ETA2
Red/Blue is an output from the AHU, pulls -ve to enable the infotainment relay so will be a trigger input to the step control module, albeit pulling down, not up, I'd probably expect to see a couple of volts on that line with it open circuit.
ETA3
White (pin 12) appears to be a switched 12V output from the AHU that powers the AM & FM antenna amplifiers, the logic appears strange as there is a switched -ve and a switched +ve - unless the switched -ve is actually an output from the step control module - but why the switched +ve as that is only switched on at the same time as the infotainment relay pulls in....

Last edited by Phoenix on 7th Mar 2023 10:50pm. Edited 1 time in total

That’s a big help, thank you.

I’ll check tomorrow to see if the Red/Green is getting any power.

I’ve just got a gut feeling that there’s something in the loom for the steps causing it. If I’m getting power at that pin, I reckon I’ll remove the loom for the steps and pin it out properly off the car. At least that way I can strip the tape off it and inspect the loom. Might even be able to figure out where the 12v feed is meant to enter the step ECU.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

David, may I start by stating the obvious... Did you check all the fuses in the car?

These things usually get confused by an ECU in the car (not necessarily the steps ECU) finding itself in "distress" hence the age-old "battery reset" I'm guessing you have done the basics first?

The fuses will most likely be OK - that's why I asked if the infotainment system was operating as expected, other than the functional power, everything else is piggy-backed from the AHU. The step control module has also had it's power reset at least twice.

I have indeed.

The battery was off the car for 48hrs whilst it was in the workshop in January. I’ve also tried a different step ECU to no avail

The steps worked great on Christmas Day, then on Boxing Day they didn’t work at all. There was no funny business or intermittent operation on the run up to them failing completely.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

Hence me asking about fuses David... Even the diddy 5amp fuses can interfere with the steps getting their signals...

I flicked through the handbook and looked for anything that might affect them but didn’t spend a lot of time on them as everything else appeared to work and there was no separate fuse listed for the steps.

I’ll have more of a rummage through them tomorrow

Thanks Craig.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

It's worth metering every fuse David... Doesnt take very much time...

The loom is very simple and basic. Taking the big power source directly from the fusebox, and as you found the piggyback plug in the TV tuner box...