That’s one test I’ve forgotten to do I must admit.

Am I right in thinking that I’d unplug the main car harness from the AHU whilst leaving the battery connected to the car and check for voltage on the CAN connections to that plug, essentially leaving the step loom disconnected?

I did test 2 pins on the switch and they switched but the pins were tiny, it was freezing and I couldn’t feel my fingers

I wish I had your knowledge and understanding of electrics, Phoenix!

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

Essentially, the AHU plug & socket that picks up the CAN & illumination needs to be disconnected from the AHU and the vehicle harness - so the only connection to the vehicle is the heavy power - obviously this means the black plug needs to be connected to the sidestep control module, the motors & the switch can be left connected.

CAN is a bi-directional communication, so even though the AHU & IPK are disconnected, the sidestep module will still send it's framing packets, these will likely give a reduced voltage measurement of around 1.7VDC. You need to do the test within around 40 seconds of powering up the sidestep module otherwise it'll assume it needs to go to reduced power mode (a.k.a.'sleep'). The purpose of the test is to check that the module can at least send and receive CAN messages to the jumper connections. MS-CAN although it uses CAN high & CAN low, can work with one leg disconnected, pulled high or pulled low so is reasonably robust, unfortunately the protocol doesn't have any method of setting DTC's for network disruption, hence the suggestion to check for voltage on both CAN wires.

RE: understanding of electrical systems, well it can be both a blessing and a curse!

It’s a shame you’re not closer to Scotland as that curse would see me booking this thing in with you

I’ll do that test tomorrow afternoon and report back.

Usually I’ve got a “If that doesn’t work I’ll try this next” sort of approach but this time I’m totally out of ideas.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

Just a thought - can you see the door status in the PATS module? if so is it plausible?
Of course, the door status shouldn't prevent the steps being initialised, parked or deployed with the switch, the only other data I can see being relevant is ignition status, gear position and road speed - if any of those were not being broadcast correctly, there would be a clutch of DTC's set in other modules.

Closer to Scotland? there's the blessing bit

Which one is the PATS module? I’ll have a look with the IID at Live Values later on and see if I can see them but I’m not sure which the PATS module is.

Another thought I had last night was the Terrain Response can also inhibit the side steps. If the car is in rock crawl mode then the steps won’t deploy when you open the door.

I’ve tried the Terrain Reponse dial last night and it shows on the screen as it toggles through the modes and when you go back to normal it shows “Special Programs Off” on the dashboard.

The message centre on the dashboard also displays “Close door to change height” if you try and change the suspension height with a door open.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

Right, new switch fitted and surprise surprise, it’s still dead.

I unplugged the step loom from the AHU completely as suggested, reconnected the ECU for the steps before measuring voltage on the 2 CAN pins. I was getting 2.4v from both CAN pins so the ECU is obviously powering and sending signals on the CAN.

I had a good look through the live values on the IID tool. One I focussed on was the “Engine Running” status through all of the ECU’s.

Engine Running:

Vehicle Dynamic ECU - Yes
Steering Angle - N/A
Running Board - N/A
Audio Amplifier - N/A
Audio System - N/A
Terrain Response - N/A
CD Player - N/A
Navigation - N/A
Instrument Pack - N/A
Parking Brake - N/A
Remote Driver - No
Suspension - N/A
Transfer Case - N/A

I noticed in the Terrain Response ECU is that it’s not reporting as being in Rock Crawl mode so the steps shouldn’t be inhibited.

One point to note is I currently have a handbrake fault on the car but the steps worked for 6 weeks after the handbrake packed in.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

Right, well the park brake could have a bearing on it, why all of a sudden, I have no clue.. I'm fairly certain that the park brake doesn't have to be applied, only the transmission needs to be in park. That said, with (presumably) a DTC set, it may be an unintended consequence. Can you clear the DTC? Even if it comes back later, if it stays off long enough for testing the steps, that should prove if it has a bearing or not. Also, it it possible to try initializing the steps with the CAN disconnected from the harness end but still connected to the AHU (so it has someone to talk to) It might do nothing if its looking for ignition and door status though.
Other than the park brake, are there any other DTC's set?
PATS is integrated into another assembly, I forget which, I'll have a look later - but it should be separately addressable.

The car is back together at the moment as I need it to use the trailer tomorrow.

I tried to release the CAN pins from the step ECU plug but I couldn’t shift them so I’ve ordered a set of tools to release the pins from these plugs.

I removed the fuse from the handbrake today too so that it wasn’t broadcasting a fault. The fault light cleared from the dashboard but the faults were stored saying it had lost communications. The steps didn’t work though.

Previously, the only thing that inhibited the steps was the terrain response. If my wife opened the door with the car in D the step would deploy when she got in or out and it’d fold in again as soon as she shut the door.

I’ve had a look at the 2012 that has steps on it today too but the IID tool doesn’t even see the Running Board ECU on that car. The steps work perfectly too.

These are the only 2 fault codes stored on the car.

Click image to enlarge

With that DTC, if it was in work we'd be looking to resolve that before going any further, the reason being it's essentially saying that packets sent are unreliable or missing, that can degrade the whole dataset. I don't know why it hasn't had any effect prior, unless there was a different, lower order DTC that was only local to the park brake.
I was wrong about the PATS, it is a discrete module but only deals with the steering lock & key transponder. The GEM, incorporated in the 'body control module' under the passenger seat deals with the active security (alarm) and has inputs from all four doors. The route onto the MS-CAN & HS-CAN is through a K-BUS gateway in the instrument pack. The door state must be getting onto at least the HS-CAN as the suspension height change inhibit on door ajar is functional.

I can't help thinking there is something fundamental that I'm missing, there should be no reason why the steps shouldn't initialise as that function only relies upon power and switch input (although I have no idea of the design decisions or the software logic involved in deciding when they should and shouldn't work!).

The only checks that haven't been done yet - and I appreciate you've done continuity checks - is volt-drop checks on the ground connections, the power connection and the switch connections. It's a lot of work to do, possibly with no benefit, but other than resolving the park brake issue, I'm running out of ideas - they should just work!

Unfortunately, fixing the park brake issue means dropping the rear subframe so it’s going to have to wait for a bit as I just don’t have time at the moment. It’d also be nice for it to be a bit warmer before I start doing that!

Thanks so much for your help, Phoenix. I’ll sort the handbrake and will let you know how I get on with the steps.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

Looking back over your parkbrake issues, TBH I'd just make an overlay harness and splice that in - no need to lower the rear subframe and would probably be only a couple of hours work. If you want a few metres of suitable twisted pairs, I'm sure I could find some.

I’ve come to the conclusion that there’s an issue with the wiring above the subframe going into the handbrake module. I can just get my hand up to unplug the connector but I can’t get enough slack on the loom to get a proper look at it unfortunately. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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 finally managed to get time to sort the parking brake issue today. When inspecting the wiring loom there was a green blob on it. It hadn’t chaffed on anything which was my initial concern.

Upon removing the insulation there was a yellow wire that had ballooned with green corrosion. Upon touching it the wire fell apart. I’ve repaired that and the handbrake now works perfectly.

Even after clearing all the fault codes the bloody steps still don’t work though

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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, I reckon you could fall into a bucket of tits and come out sucking your thumb pal!

I wouldn’t go that far.

Annoyingly, I fitted these to my L322 as the wife liked the ones on my Dads car. They worked for 3.5 months and one day just stopped and I can’t figure out why.

I just like things to work as they should. Especially seeing as jacking this one or getting it on a 2 post lift is now a pain in the arse with them stuck in!

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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