Disco TD5 Auto electrical issues

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landyboots

Active Member
Posts
330
Location
Republic of Austerity
Hi all.....Just wondering can anyone help. I have 2001 disco td5 auto which has now developed electrical issues. The fuel flap has stopped working. The gearbox display on the instrument pack and the centre console displays park when I start the car and stays displaying park when I select any other gear. The car drives fine and changes gears as normal.:confused: some other systems i.e. the rear wiper, front and rear fog lights, all electric windows, front intermittent wipers and the heated rear screen don't work either and the ignition illumination doesn't happen. The interior lights work on the switches but don't illuminate when doors are opened....If I disconnect the battery and reconnect it again, turn ignition to position 2, all these systems work again but, as soon as I start the car the problems re-occur. Has any of you very knowledgeable guys out there suffered similar issues?....Any help at all would be much appreciated as I am at my wits end with this problem and it's no fun looking at the disco lying in my yard with no NCT (MOT) because of this.

Many thanks for looking guys.
 
If it all went wrong at the same time the common denominator would appear to be a dodgy connection at the ignition switch..........however.

If this is a list of faults that have appeared over a period of time..... It'll be a bit trickier.

Basic electrical fault finding is fairly simple as long as you follow a logical sequence.

This list can be used top to bottom or visa versa using circuit diagram and a leadlight or multimeter.

Check for a voltage at the fuse or power
feed to the unit.
Check for voltage at the unit.
Use the lead to provide a secondry earth from the unit.

What happens next depends what you find!
 
landyboots said:
Hi all.....Just wondering can anyone help. I have 2001 disco td5 auto which has now developed electrical issues. The fuel flap has stopped working. The gearbox display on the instrument pack and the centre console displays park when I start the car and stays displaying park when I select any other gear. The car drives fine and changes gears as normal.:confused: some other systems i.e. the rear wiper, front and rear fog lights, all electric windows, front intermittent wipers and the heated rear screen don't work either and the ignition illumination doesn't happen. The interior lights work on the switches but don't illuminate when doors are opened....If I disconnect the battery and reconnect it again, turn ignition to position 2, all these systems work again but, as soon as I start the car the problems re-occur. Has any of you very knowledgeable guys out there suffered similar issues?....Any help at all would be much appreciated as I am at my wits end with this problem and it's no fun looking at the disco lying in my yard with no NCT (MOT) because of this.

Many thanks for looking guys.
Click to expand...

First of all check for corrosion in plugs/water ingress at the interior fusebox(compartment under the steering wheel) and at the BCU(behind the glovebox) ...one of these two is making tricks...if everything is dry and the plugs are OK report back and i'll tell you how to identify the guilty part cos then maybe it will have to be replaced with a good one
 
Thanks for the reply's guys.....

I have taken the underbonnet and passenger compartment fuseboxes out, checked, cleaned and applied contact spray to all plugs and sockets. I seen somewhere here before that the passenger fuse box contains the IDM and can sometimes suffer from water penetration and corroded tracking on the circuit board. Mine was perfect. I had a quick look at the BCU from under the footwell panel. I disconected the 4 plugs from underneath, had a quick look and sprayed them with contact cleaner. All good there. I know there is another plug on the side of the BCU that I couldn't get to so it's off with the glove box and out with the BCU some time today. I was considering an earth fault somewhere but I can't understand why everything works perfect when ignition is switched to position 2. It's only when I switch to position 3 and start the engine that all the faults occur. I would have imagined that an earth fault is either present or not. I have gone through every system with my Nanocom and no faults are present. The only issue I noticed is when I communicate with the BCU inputs in body 1 the gear position park/neutral is off when the gear selector is in park or neutral and it is shown as on when I select reverse:doh:......However, in body 2 inputs the park/neutral is on when in park or neutral, as it should be. So, a contradiction there.....

Thanks again for your help guys. I am no electrical wiz so, if yous keep offering your opinions, maybe we can work this out together.:)
 
Thanks Bromsgrove. Yes, that's the irony of it. Intermittent faults:mad2:
The thing is it's not intermittent. It's totaly consistent. Disconnect battery, ignition to position 2 everything works. Ignition to position 3, car starts, all faults appear. If I switch off and switch on to position 2, all faults remain. I have to disconnect battery or remove fuse 13 from the engine bay fusebox and refit fuse or reconnect battery to get them to behave in ignition position 2 again....
Keep up with the help guys and hopefully we can get to the bottom of this.

It's off to the BCU for me now:(
 
Bromsgrove Defender said:
Yup an earth fault can be either present or not ;)






Normally present, at a really inconvenient moment :mad:

and then

Not present, when you try to find it :rolleyes:
Click to expand...

^^^:) +1 ... the two earths for the BCU are coming from these headers... also near Coo17 is the plug which connects to the courtesy lights...check all connections there, it uset to get water there too
 

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Thanks for that Sierraferry..... I'm off to check these out along with the BCU itself. Will post back with my findings.

Really greatfull for the help guys.

I intend to keep this going to it's conclusion so we can help someone to resolve similarly frustrating issues....
 
Appologies Sierraferry. Cross posting there.....

Yes, the Nanocom communicates with the BCU while faults are present but I did notice that sometimes the comms breaks down and I have to come out of BCU and go back in to establish comms again......
 
a main earth and the battery supply for the BCU goes to that lateral plug which you didnt check...tha fact that loses communication leads to some fault connected or within the BCU
 
Last edited:
landyboots said:
Feel like I'm getting somewhere now.....Hopefully that is the culprit.

Will post back sierraferry.

Thanks again.
Click to expand...


It may also be a battery fault. As with most modern cars the DII has many electronic systems which need a reliable source of volts.

If your car battery is starting to fail, it may still have enough juice to spin the engine but during the starting procedure one or more of the ecu's could be starved of volts.
 
Thanks for that Thebiglad.....Yes, I did consider that. I was wondering was it power interruption to ECU's on startup because everything is denied power on startup. The radio going off and going back on again would prove this but This happens to all vehicles and I'd imagine it's compensated for in the design of the electronic systems in all modern vehicles with such complex electronics. The Battery has been exchanged for a new one as a first action and the Nanocom is
showing 14.2 v in all systems while the vehicle is running and showing 11.8volts to 12.2 volts while in ignition position 2.....Within range I would have thought.

Thanks for your input....
 
landyboots said:
Thanks for that Thebiglad... The Battery has been exchanged for a new one as a first action and the Nanocom is
showing 14.2 v in all systems while the vehicle is running and showing 11.8volts to 12.2 volts while in ignition position 2.....Within range I would have thought.

Thanks for your input....
Click to expand...

That looks slightly low to me, but in any case has little to do with how the battery performs under the load of the starter motor.

If it were mine I would have it on charge overnight and then see.

Incidently, re your general comment about car designers taking a failing battery into account -speak to Audi, Merc BMW and Jaguar owners. Loads of them report haphazard failings like yours that are completely cured by having a fully charged new battery.

What have you got to lose by charging it up overnight?
 
Point taken thebiglad.....Like I said, electrics aren't my strongest point but that's why I get on to you guys..... All the help and pointers I get from yous are helping me to make progress and with help from the Nanocom I am confident I can crack this. Thanks all.....

By the way, I have solved the courtesy lighting issue. Tracked it to the passenger door switch. I never noticed while using Nanocom that the door switch was showing as open with the door closed. This revealed itself when I broke the two connector blocks behind the footwell side panel, cleaned and re-connected them and the courtesy lights illuminated so thanks Sierrafery for that.
I had to leave one of the connectors apart as the lights won't extinguish so now they illuminate and go out when I open and close all the other doors:)

Keep the hints and pointers coming guys....
 
All door switches and bonnet switch aswell are opened with the doors/bonnet closed cos that's how it works for the systems... when one door or the bonnet is opened the switch closes giving earth to the BCU which activates the involved systems(alarm, courtesy lights, SLS, etc)...that's how it knows what was opened cos they are "splitted" in 3 circuits: the drivers door, all the other doors, the bonnet.

the courtesy lights will stay on 10 minutes if a door is opened and 15 seconds after you closed the door not immediately, also if the 10 min elapsed they will not work again untill you turn ignition on... they have a timer in the BCU
 
Thanks for that explanation sierrafery.....so what you are saying is it's a three way system i.e. 3 earth paths to one header and all are switched by the opening of a door or bonnet by providing a closed switch in the opened latch:confused:
I think I grasp the workings of it now....Anyway, the Nanocom highlited that the passenger door was open when it was closed and all other doors and bonnet where highlited as closed. So it could have been any of the passenger doors that was the problem....pot luck I guess....

Just an update on my efforts to tackle everything else. I removed both footwell side panels and broke all connector blocks and earth headers including the one under the driver footwell carpet. Cleaned them all up and sprayed with contact cleaner. I noticed the bottom connector block of the two that are clipped to the A post panel on the passenger side, top one is brown and the bottom one is white, was showing the green powdery signs of corrosion. the two pins right at the bottom were particularly bad. there is a purple wire with a blue tracer connected to one pin and a pink or white wire I think with a purple tracer connected to the other pin. Does anyone know what these are for???
I cleaned them up as best I could and connected everything back up but no, the problems still remain. I removed the BCU and opened it to check for water damage but it was perfect and all the connectors were clean. Cleaned everything once again and sprayed with contact cleaner. put everything back in place and no joy. Problems still remain.....

I'm now hoping for a eureka moment....

Any more ideas would be greatly appreciated guys.

Thanks for all the inputs up to now....
 
it's hard to identify a circuit just out of a verbal description... imo unfortunately you can rely just on luck to find a fault without ruleing out the BCU first... cos these used to fail even without water ingress... for further diagnose you need at least basic electronics knowledge to make measurements on the earths and inputs at the BCU's plugs...and for that you must trace the wires based on the diagrams and operation mode...so if you dont have one download a RAVE and there you find everything
 
Hi Sierra.....You have been of immense help and I see your knowledge of electronics far exceeds mine:(......I have the Rave manual downloaded but unfortunately I struggle to make much sense of it. This problem could be caused by so many things it's just the process of elimination now......Starting to think BCU is corrupted somehow. I think it might have given trouble before as when I had it out I noticed the casing was badly scratched and there was a heat dent in it that looked like it was caused by a soldering iron.....

Do you know of any reliable companies who test them?

Thanks again for your help.
 
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