Just off the phone with Bell Engineering. What is interesting is that he was surprised that our error message says "Transmission Fault", not "Transmission Fault Traction Reduced". I must say I had assumed that was just to do with with the exact model. Anyway there were a few tests he suggested, so I have something to try at least.
(1) Does rear wheel drive actually engage?
(2) Does error message of code change if vehicle wiring disconnected, or pump wiring disconnect?
(3) Check for corrosion of ECU PCB or connectors ----------
Tony S

Great, and I hope you will keep us informed with the outcome

Clive If it ain't ***ked don't fix it

And the results are in, but stupidly I forgot to ask Bell what the results one way or another would suggest ..
(1) Rear wheel drive not engaging, tested by heading up a slope on wet grass, but being a bit rougher than I would normally drive I could spin the front wheels quite easily. Would have been a better test if the slope had been steep enough or slippery enough that it simply couldn't get up on front wheel drive only
(2) Error codes unchanged if either vehicle wiring connector, or pump connector disconnected

Further playing with a code reader. Previously I just did an automatic scan which collected error codes from a number of modules (ABS, ATCM etc) and in each case the module reports a fault code saying it can't talk to the rear differential control module. Playing a bit more you can select which module you want to query, so for example if I select ABS or ATCM or BCM then it shows options to display ECU info (serial numbers, version etc), fault codes, and some other options. If I ask it to check the RDCM it simply says it no communication.

Not sure what all this implies.

A local garage that I spoke to this afternoon sounded quite on the ball, for example the technician referred to them normally using a VW part instead of Land Rover if replacing the pump. He seemed confident they could diagnose it down to ECU / Pump or other component without dismantling. Interestingly he said that pump was the most common fault, where Bell said ECU more likely. ----------
Tony S

The results are a bit ambiguous, it can be the fuse, it can be the wiring, it can be the ECU, it can be the pump.
Fuses you have checked
Wiring ??????
ECU can be checked with a second ECU and is some to do
Pump can be removed and checked.

It's now up to you, who when where and which

Sorry but that is how I see it .

Good luck and keep us informed

Clive (in sunny Menorca) If it ain't ***ked don't fix it

The only wiring check I think I could have missed was ground continuity, there are two ground wires on the connector but I suspect I only used one on my tests. The car's back up on ramps at home so that is a quick check I might as well carry out. ----------
Tony S

When you disconnect the ECU spray some contact cleaner on the pins

Good luck

Unfortunately it is looking like ECU or Haldex pump If it ain't ***ked don't fix it

Cheers, this is where it gets frustrating with the unknowns. Does anyone happen to know if the ECU can be removed and refitted without the need to new gaskets and/or fluid replacement? If I'm going to do anything that immobilises the vehicle, I won't do that while I'm still undecided about taking it to the local garage. ----------
Tony S

Its a year since I had all my MY 2010 apart to service the haldex and change the diff but this is what I can remember:

I definiely did not change the Haldex ECU unit seal - I cleaned up the exiting seal / seals and re-used.

The ECU unit has an electrical connector that push fits onto a connector on top of a multi-seal piston in the haldex. If you pull the ECU unit off and this piston unit comes with it then I'm pretty sure that you will lose haldex fluid out of the resulting hole. FL2 HSE Auto Galway Green
Evoque SD4 Auto Blue.
FL1 HSE TD4 Manual Black - Gone.
RR Classic V8 EFI - Gone

Any news yet Tony

Clive If it ain't ***ked don't fix it

Not yet. Car's sitting in the barn on wheel ramps. It will be a week or so until I could get it into the garage, if I go that route but at the moment I'm wondering whether to just take a punt on a second hand ECU. ----------
Tony S

Ask the question on here if anybody has one or go to eBay and look or go to one of these second hand car parts website where you say what you want and they come back with offers.
I will keep my ear to the ground for you.
Clive. If it ain't ***ked don't fix it

Sorry if this is obvious or I have misunderstood, but when you clear the faults, do they immediately come back up or only when you turn on the engine and drive? Would a physical fault with the Haldex not only alert the ECU once it is running whereas a wiring fault to the ECU would give an immediate error code?

I stalled the car at a busy mini roundabout/zebra crossing combo a couple of weeks ago and the immediate restart gave me the Special Programmes Off warning. Error codes were U0136-00 (68 ) and U0415-94 (2C) but, once cleared, these have not recurred (or at least not in the subsequent 1700 miles). My assumption is a simple communication glitch caused by incorrect shut down and rushed re-start. I also assume that if I hadn’t been able to clear the codes, I would now have been taking it in for Haldex investigation, presumably quite needlessly. 2005 D3 2.7 Auto
Previously:
2010 MY FL2 TD4e GS - Now gone at 199,500 miles, about 135,000 of them mine.
‘93 Defender 110 200TDi CSW
‘87 Defender 90 4 cyl Petrol
‘83 110 CSW V8 - best ever!
Range Rover 2-door V8 (not sure of year - 4-speed box and vacuum diff switch)
Series III SWB Diesel

To answer the last question, the fault codes come back immediately after being erases. Moving on I have just tried a second hand ECU and the symptoms are exactly the same ..
- DTC U0136-00 or U136-87 from various modules like ABS ATCM etc, complaining they've lost contact with RDCM
- Query RDCM directly and there's no response, exactly as if it wasn't there at al
- Same symptoms with the pump connector disconnected from ECU

Checked earth and switched live connectivity on the connector again. The only thing left I think is to see if I can test the Canbus - is it actually sending sensible message to the ECU. ----------
Tony S

Yet more checks and now I'm pretty certain there's a problem with the power. I measure 12V (or whatever) at the connector, but when I connect a small load (motorcycle indicator) the voltage drops to zero. The problem is on the supply side, checked by adding a ground cable from the battery -ve. Voltage at the fuse is unchanged, so I'm losing it somewhere between the fuse and the connector.

I'm having trouble tracing the harness, from the RDCM the wiring goes up above a crossmember where I can't even reach with a finger, let alone see where it goes. From there I haven't the foggiest idea how it makes it's way to the rear fusebox.

Any suggestions for chasing this down? Even if I could just find a route between fusebox and the RDCM I could run a new +ve cable and splice that in somehow. ----------
Tony S

Tony
If you are losing voltage under load, there must be high resistance / corrosion in the power lead.
After cleaning the connector and fuse ... pins/blades/sockets try rigging up a resistance check from fuse output to RDCM connector and wiggle the wiring loom.
I have looked at Repair Manual but I cannot see any drawing of the Rear Wiring Harness run.( Luggage compartment fuse box )
Ian FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 76k+ miles) (MY2015)