Possible Earth fault causing Defender TD5 issues.

hi guys,
I have a Defender TD5 on a 52 plate.

About three months ago it was driving nicely and then cut out at a roundabout. The engine warning light came on and the throttle was dead.

After faffing about with known, good spares - no real fault could be found. We swapped the ECU and the pedal assembly etc and we couldn't find a fault. When we put the whole lot back to the original parts it all worked. I love an intermittent fault!
One thing we did discover was that the engine management light would not trigger if the engine was started with the throttle depressed. At the time we did assume an earthing fault.
Anyway, now I have the same thing again, only this time accompanied by the following: intermittent courtesy light illumination, intermittent hand brake warning light, intermittent dashboard illumination failures, as well as an intermittent engine warning light and throttle failure. As well as all that the battery totally discharged over night the other night (that could be the courtesy light doing it's thing again). It's a new battery.

Has anyone got any ideas on this? Could it be an earth fault, and if so where are some pertinent earthing points? Basically with garage time at premium rates (with no guarantee of a fix) I gotta diagnose this baby myself.

I would really appreciate some input on this one.

Regards,

On the drivers side of the transfer box there is 2 main earths ring terminals. This would be my first guess. Remove, clean and refit.

Hiya,
OK, this might sound a little lame, but when you say on the drivers side of the transfer box are we talking about the little cubby under the drivers seat where the ECU resides?

Run a temporary earth direct from the battery -ve to the ECU earth point. Also run a heavy temporary earth cable (you can use a boost cable) from the battery -ve to the engine block. If it solves your starting problem then you need to clean and tighten all the main earth points.

All the other faults sound like earth faults although water ingress can cause em too. Often the lack of throttle pedal can be down to a chafed wire that runs the throttle pot. If you stick it on a diagnostic pooter and scan the live data you will probably find the 5v feed missing.

As per Ratty's answer, don't forget the condition of the wiring looms themselves. When I got my TD5 last year it started showing up some faults that turned out to be deterioration of the loom. At first I looked for e.g. accelerator potentiometer faults, oil in loom, relays, connections, sensors etc. but they were all OK. A few other people have had this sort of problem too. Land Rover seem to have had a batch of cable that tends to go brittle at some point in the mid 2000s

Well today I got under the Landy and have done the following;
Cleaned the main earthing points from the battey to the chassis and transfer box.
Had the dash out and cleaned up the earthing poins on the metal strap behind the instrument binicle.
Cleaned the earthing point in the cubby box under the drivers seat (where the ECU is located).

I am still getting engine warning light on 50% of starts and intermittently when I take my foot off the throttle.

Are there any other points people know of? I am going to run a cable from battery -ive to the ECU to check the earthing but I need to know how the ECU is earthed (through it's casing?).

I'm still thinking about faults in the wiring loom itself. In doing all this earth point cleaning you probably jiggled the looms about which might make a difference to the frequency of the fault. In my case the major part of the problem lay in the wires between the ECU and the accelerator pedal (or 'driver demand' as some of the manuals call it).

I can't remember offhand which of the wires in the ECU plugs are earths, but it seems to be mostly the black ones - yes there are quite a number of them.

Today's installment. Checked the ECU feed from the engine. The round plug was pretty oily and wet. Replaced the ECU loom. Not a major job. It had no effect on the problem.
Have run earths everywhere. No joy.
I am getting the fault before the engine cranks. The dashboard lights come on, I can hear the fuel pump running, all the correct lights go out and then the engine management light comes on, but as ever, only intermittently. Ssometimes I can it try the ignition and everything stays out. Tried a test drive earlier and only got about 50 yards before the EM light came on and I was left with no throttle. DOH!

Spoke to Westover landrover today in Christchurch. The guy there suggested checking the MAP sensor and giving all the sensors a bit of a clean in case moisture or dirt was the issue. Unfortunately his TD5 expert was off today, so he couldn't give me much indication where to look for the sensor and where else to check and clean. He did say that he had exactly the same trouble with his and it was the MAP sensor in the end.

I am going out of my head. I'm stuck in the sticks with no car and precious little idea where to go from here.

Tomorrow we get the RAC out to put a computer on it... I gotta feeling all it going to say is what it said months ago when this happened... 'Throttle fault'.

Just found a good link on here re. The MAP sensor. Is this just wishful thinking that it could be causing this problem?

My thinking is that this is happening before the engine cranks and fires (or compresses - diesel) so my thinking is that fuel, and other issues wouldn't effect the process. I could understand if this was happening under throttle...

Havnt read the whole thread but a similar thing happend to mine except going down the M40...

Was a bad earth, battery/gearbox.

Also had the same response from diagnostics but was not the throttle.

Due to need it back on the road I called an Autosparks they sorted the problem in under an hour for £55 inc cable etc..

Could be the MAP or the MAF clean both up. Dont suppose youve changed the injector loom?

Changed the injector loom, redid all the earth straps etc. I am on sensor cleaning tomorrow...

bankz5152 said:

Havnt read the whole thread but a similar thing happend to mine except going down the M40...

Was a bad earth, battery/gearbox.

Also had the same response from diagnostics but was not the throttle.

Due to need it back on the road I called an Autosparks they sorted the problem in under an hour for £55 inc cable etc..

Could be the MAP or the MAF clean both up. Dont suppose youve changed the injector loom?

Click to expand...

As bankz says, it's worth checking the maf and map as IIRC they share the same 5v feed as the throttle pot. If you do get the Rac out with their pooter get em to bring up the live data and make sure the pot is getting the full voltage that it needs.

The earth I was talking about is under the seatbox. If you look backwards from the front output of your transfer box there are 2 ring terminals on the side of the transfer box next to the chassis rail held by an M8 flanged head bolt with a 10mm head.

Thats the one the was doing me in.

had the AA out. Their diagnostics are a bit 'generic'. Basically we have fault codes 091,092,093,094,113,120

Anyone in the Wimborne/Ringwood area fancy joining me for coffee, lunch and some tests with their working accelerator pedal before I have to go down the route of expensive 'suck it and see' spare parts surgery?

Have you checked those earths?

Try a proper auto sparks first

BoredRigid said:

had the AA out. Their diagnostics are a bit 'generic'. Basically we have fault codes 091,092,093,094,113,120

Anyone in the Wimborne/Ringwood area fancy joining me for coffee, lunch and some tests with their working accelerator pedal before I have to go down the route of expensive 'suck it and see' spare parts surgery?

Click to expand...

091 to 094 off the top of my head are extras that aren't fitted to your vehicle such as tacho open load faults, air con and auto box. I can't remember exactly what each one is.

Iirc 113 is a driver demand error and 120 is a communication error to the Ecu, Both of which could be due to the loss of feed from the throttle pot. Check out the wiring on the throttle and there should be a white and purple wire that goes to the Ecu. I believe it is PIN number 14 on the black plug of the Ecu. You could try running a fresh cable between these points and see if that cures it. If that is beyond your capabilities then you could sply try flexing the loom around the Ecu and see if it brings the throttle back. I've had a couple of the wires to my Ecu nearly snap after going brittle.

If the guy brought up the live data and checked the voltage at the throttle pot it would have confirmed or denied this straight away.

Like i said in a previous post the exact same thing happend to mine. Right down to the fault codes. Yet its 1 year on my throttles been drowned many times and is golden. No issues at all.

Was a bad battery earth and another (see my own td5 issue thread in Jan/Feb I think)