This has got me baffled.
Had an issue last week were car wouldn't start when I was collecting my daughter. Eventually got it going and on returning home found the battery earth terminal to be a little loose. Tightened it up and all good again or so I thought.
The folllowing day whilst on a trip out with the horse box on the car cut out suddenly on a trunk road junction roundabout and wouldn't restart. Being in a predicament had to call the AA.
I had tried calling up fault codes with my foxwell reader but saying couldn't read vin from dash so no go.
AA man turned up and found battery voltage low. Put it on boost and no joy. It did eventually start a couple of times an then cut out after a few minutes and ended up being recovered to home as it was a Sunday.

I' was convinced it was an ignition switch issue as all lights come on dash but no cranking. I also had a similar cut out and dead issue with a previous tdV8.
So I've replaced the ignition switch but no joy. Changed battery over to a known good one from another vehicle.
I can get the engine to crank by removing the relay in fuse box and jumping contacts, engine spins over OK so not a starter or battery fault.
Battery voltage reading is 12.6 volts with my multi-meter.
I can access all modules on diagnostic reader except the engine ECU PCM module.
All lights are on the dash just no cranking and start, regardless of whether in gas or petrol mode.
One strange one is that all lights work except brake lights. Live data from ECU doesn't recognize the brake switch as active even when pressed.
I've checked all fuses under bonnet and behind glove box and all OK.
I've checked all earths in the ecu fuse box area under bonnet and all seem OK, test same as full voltage from battery.

One issue I did have previously was two rear ABS sensors inoperative after changing lower arms. The new britpart ones didn't seem to be liked by the car and hadn't got round to getting genuine ones.

Anyone got any thoughts on further likely issues?

Engine ecu powers with ign on, so 12v are Pins B4, B6, B17, B30 and B54.

Grounds are B1, B2, B3, B5.

I see two more relay controlled powers in A95 and B50.

Bank B is the smaller connector on the engine ecu. 2006 4.2 SC

Thanks Spud,

I'll do a bit more testing tomorrow with the meter when the rain has stopped.
Any idea where those relays are?
I've registered for topix but haven't got into it to have a look so far.

Main relay R1 is in the E box under the bonnet.

The other two are fed via the main relay and would not contribute to an ecu no comms scenario. 2006 4.2 SC

If you can start it by jumping the pins of the relay, have you tried replacing the relay?

Sorry if I'm stating the obvious but it's worth checking the simple things first

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

I can get the engine to turn over / crank by jumping the relay but it doesn't start.

It won't start if you do it that way I wouldn't think as the rest of the car doesn't see it turning over. The immobiliser will still be on as well I'd have thought.

See if there's a relay that's the same and swap them temporarily. It could be something as simple as a burnt relay that's not closing when it should do. It'll likely do nothing but it's a free and very simple thing to check

When you energise the starter with the key, there will be 12v going to that relay which will pull the contacts shut. When using the paper clip you are effectively pulling the contacts shut which is why the engine turns. You could check between the other pins on the relay to see if you're getting 12v.

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

Spud wrote:

Engine ecu powers with ign on, so 12v are Pins B4, B6, B17, B30 and B54.

Grounds are B1, B2, B3, B5.

I see two more relay controlled powers in A95 and B50.

Bank B is the smaller connector on the engine ecu.

Looks like you've lost ign supply at terminal 15 ( power to B17 ). I could understand no power to B30 from terminal 15 as it's fused. But B17 is supposed to be direct, so i would start from there.

Maybe the diagram helps.




 2006 4.2 SC

if the brake lights do not work and you need to press the break pedal to get it started is it worth checking these first?
if you dont have your foot on the break it will not run.
just a thought 2012 Vogue 4.4 TDV8 - Current
2014 Navara V6 - Gone
2004 Vogue TD6 - Gone
Grand Cherokee - Gone
Discovery V8 (LPG) - Gone
Discovery TD5 - Gone

No need to apply brakes to start on 2006 model. Only need to apply brakes shift out of park.

I'll admit I had to double check in the manual that I wasn't fooling myself. I'm usually in the habit of holding the brakes on whilst starting anyway ready to shift into gear.

Spud wrote:

Looks like you've lost ign supply at terminal 15 ( power to B17 ). I could understand no power to B30 from terminal 15 as it's fused. But B17 is supposed to be direct, so i would start from there.

Maybe the diagram helps.

Jumping R3 just triggers the pump in ABS unit.
R7 is direct to starter motor.

Click image to enlarge

In the E box you should have a bank of five normal size blade fuses.

F1

(30A) Engine control module(ECM) (Diesel)

F2

(30A) Variable valve lift control module (petrol)

F3

(30A) Heated oxygen sensors (HO2S) (petrol)

F4

(30A) Engine control module(ECM) (petrol)

F5

(30A) Ignition system (petrol)



 2006 4.2 SC

That seems to be showing an early version of the E fuse box.

Mine is as per earlier attached image.