Discovery 2 td5 electric problem

Hello, i have an issue with my td5.
Let me explain.

July 21, 2017
Car drops to the bump stops on the rear suspension airbags. After start it rises, next day it shows the same issue.

August 2, 2017
Car did not start, turning the ignition key to start position, all lights went out starter engine does not turn over. After taking a hammer and hitting the starter motor the engine kicked into live again. (I now think this was a coincidence and the car was immobilized which was reset when waiting for some time).

The P1843 CAN timeout failure was registered and could be erased.

Later that day the same as above occurred again.
Checked to power on all ECU's and the BCU and EAT were at 11.6 volt where all others were on 12,3 volt.
I found the earth terminal of the battery to the car body to be corroded (big lead to bottom terminal just behind the battery) changed the lead to a non corroded connection just above it and on returning home created a new clean earth)

Check voltage readings on all ECU's they were now within 0,1 to 0,2 volt of each other.

Since then not see again until 31-8-2017

31-8-2017
The day before the car was going like a race car very fast.

This morning the car did not start, the hammer was used at the starter motor with no effect. When checking the status of the BCU and the Auto transmission comp. for errors the P1843 CAN timeout failure was registered.

Trying to erase the fault did not work it came back again and again.

Later that day I started the car, the limp-home mode was off, the lights (M&S) of the transmission comp. did not illuminate. The fault was still in the comp. and would now clear.

Checked the power of the ecu's:
General power 12,39 volt
ECU engine 12,73 volt
SLAB ABS Bat 12,38volt, ECU power 12,38volt
BCU 11,6 Volt, Relay 11,6 volt
IDM battery 11,9 volt
ACE 12,10 volt
Gearbox ECU 11,8 / 12 volt

Next morning the car would not start, no crank nothing (the morning was damp fog in the air) when the sun came out and 1/2 hour later the car started immediately.

My conclusion was starter engine.

1-9-2017
unbolted the fuse box in the passenger compartment, checked it inside out found no signs of corrosion or overheating. Al plugs fitted correctly.
Then checked the BCU for signs of corrosion, non to be found also no signs of overheating, unit looked fine.

Then I found a SRS fault code 8 driver airbag intermittent open circuit, checking the lead under the driver seat for the SRS tensioner, cleaned it and gone was the fault.

Al reconnected and tested no faults in any of the computers, car would start.

2-9-2017
7.30 damp morning, car does not start. 1 hour later when the sun is out it starts.

At test via nanocom, power in IDM is 12,1 volt. When ignition is switched on the engine starts but then cuts out after 1 second, new start not possible BCU relay power is 0 volt, the power reading on the idm is 25,5 volt. Guess this is what you call immobilizationAfter locking the car en unlocking the engine will start again.

I attribute the error to simultaneous read-out on the. Nanocam and starting the engine, power is cycled on the BCU and IDM which I expected caused the fault.

A New code Code p0705 position switch emerges

3-9-2017
Car will not start again, however I no check whether it will start after I switch the auto box from park to neutral and back. It then starts and keeps on running.

4-9-2017
7:30 Same foggy conditions, car starts immediately!

18:30 on returning home the self leveling suspension has lowered to drop the car on to the axel. After starting the bags inflate, the next morning the car is still at normal hight.

Need to check the bags for air leaks.

Question: could the BCU trigger the SLAB to drop the car. If so I would expect this not to happen when the car is not powered up, correct?

After checking all kinds of blog's I have not been able to come to a conclusion as to where the fault is. The fact that the can bus failure was the second to occur and then all the other non starting issue came about + the trigger of SRS and Self leveling issue leads me to believe the BCU is the most likely point. However the 300+ Euro's when it could also be the XYZ for the same 300+ makes me wonder.

Any help from this audience.

Hi Oscar,

If you want to rule out / prove the bags or pipes leading to them are / not the issue then you could try the emergency valve kit.

Available from ebay. search this number on there. 272726635249

Cheers

neilly said:

Hi Oscar,

If you want to rule out / prove the bags or pipes leading to them are / not the issue then you could try the emergency valve kit.

Available from ebay. search this number on there. 272726635249

Cheers

Click to expand...

Thx for yoiur info. Good to know and to have when traveling remote areas. I check the bags this weekend for leaks.
My issue for now is more the electric non starter issue.

From what you're describing, I would say that you have a number of troubles here.
First of all, there's your rear suspension problems, and while many people will advise you test them with soapy water, personally I would advocate replacing the air bags rather than trying to over-analyse the problem. At least with new bags in place you can rule them out as a cause of the fault.
Many times, testing the bags with a soapy water spray will not show a problem, even though one exists. Change them before you go any further, and change both as a pair, at the same time. Once you have the suspension sorted out you can concentrate on your gearbox problems.
A good explanation and description of the SLS can be found at:- https://www.landyzone.co.uk/land-rover/disco-ii-air-suspension-–-the-definitive-guide.61211/
There are connections between the BCU and SLABS; one signal from SLABS to the BCU to sound the chimes when the height is being changed by the ORM switch and another connection from the BCU to SLABS to raise or lower the suspension using the optional remote controller. The BCU doesn't control the power to SLABS.
The door switches interact directly with SLABS, not via the BCU.
As far as I'm aware, the Disco 2 Td5 is not fitted with a CANBUS system.
The Supplementary Restraint System (SRS) is a "stand alone" system the SRS light on the dashboard is fed directly from the Diagnostic and Control Unit (DCU).

Thanks for this info.
From the error messages i deduct that there is a can bus as it states P1843 CAN timeout failure. Which seems to be a serial 10.400 baut signal between BCU, EAT and ECU. The main issue i had was more of a non starter immobelisation error when all the others cam e around the same time. Rulling out the SLS and SRS is a good start.
At first i thought it to be a voltage / earthing issue as the difference in power between the computers was around 0,7 volt.

Oscar H.M. De Vries said:

Thanks for this info.
From the error messages i deduct that there is a can bus as it states P1843 CAN timeout failure. Which seems to be a serial 10.400 baut signal between BCU, EAT and ECU. The main issue i had was more of a non starter immobelisation error when all the others cam e around the same time. Rulling out the SLS and SRS is a good start.
At first i thought it to be a voltage / earthing issue as the difference in power between the computers was around 0,7 volt.

Click to expand...

BCU, EAT and ECU? Are we talking about a Discovery 2 or a Range Rover?
The Discovery 2 doesn't have an EAT, just the SLABS (Self Levelling and Anti-lock Braking System).
The only place where a digital circuit exists is between the BCU and IDM.

I am talking about a discovery 2 2004, td5 automatic transmission. I thought the EAT was short for the automstic transmission ecu under the driver seat in my LHD disco.

My fault, yes, you're correct, the EAT ECU is the auto-box control unit. However from what I can see in RAVE the connections to the BCU and SLABS are DC voltage signals (+12 volts) and not digital. These signals seem to originate mainly in the XYZ switch. From RAVE, "The Park/Neutral contacts output to the BCU and, on diesel models, the ECM. The Reverse contacts output to the BCU, the reversing lamps, the SLABS ECU and, where fitted, the ACE ECU and the electrochromic interior mirror."
I don't know whether the signal to SLABS is to the suspension side or to the braking side, but I can't see how the auto-box ECU could tell the air bags to deflate.

Correct, however the synchronization between EAT, BCU and ECU is done using a serial code ove rthe CAN line.

Let's forget the SLS for the. Oment i think this has to be fixed separately.

I have 2 issues which i can't seem to relate.
1- the ETA has a P1843 Can sync failure, can be erased.
2- the engine will not start, immobelized. Wil start when gear box is switched from p to r and back

The connection in all this to me seems to be the BCU. XYZ goes to BCU and then to ECU, BCU is connected to IDM and EAT for sync. However i can't find anything wrong with the BCU.

Do you know a party in the UK that can test and possibly repair BCU's

Have you taken a look at the red plug on the engine ECU? It can very often become contaminated by stray engine oil running back down the injector wires and that can cause all manner of troubles. The interface between the Engine ECU and the other control units you're having trouble with is also on that plug.
Do you have RAVE for the Disco 2?
It can be downloaded free from:-
http://www.green-oval.com/data/lr/rave01.iso

Thanks, Yes I have the RAVE for disco 2 and also all the electronic schematics, connector plug handbooks etc.
I am the second owner of this care and have done 210K of the 315 that are on the clock right now.
I have checked the ECU there was a little contamination (I check and if needed clean it every 3 month's,. The injector loom has been changed 2 years ago, before that the oil drip was far worse. Now I have a light shine each 10K and I drive approach 25 per year) the only connections affected are the 6 bottom pins which are for the injector loom. I know of the issues that can arrize however the items I see now give me the idea that the issue is somewhere else. I am excluding the alternator, have ordered new contacts to make sure the contacts are oke and it is not a stuck plunger.

Hi, it might be simpler than you think, when it does the no-crank trick again check the lucar connector on the starter solenoid to be well tightened and if it is swap relays R2(starter) with R3(headlamp wash) to rule it out, if still no joy let it in neutral remove relay R2 and bridge the perpendicular cavities in the fusebox, if it still doesnt crank the starter is gone, you have to fix this cranking issue first cos the CAN timeout or any other fault code can be triggered by the ignition on crank request not followed in short time by crank signal to confirm the engine is running cos the CAN comms are cut when the ignition is on and the engine is not running run for a predetermined time(i dont exactly know how many seconds cos it's not described well), it's not immobilised as long as it's unlocked with the fob and the red led on dash is not continuos... the SLS thing IMO is not related and can be a simple intermittent leak, that's how they start.

Thanks, I have ordered some parts to do an overhaul on the alternator first. Will take the sls seperately and see where that leaves me. Thanks also for the check procedure.

I have a folow-up question. The starter has been overhauled the contacts were errode signle side to just under 1/5 a mm. so that is fine now.
The engine still does not want to start. What do you mean by " the perpendicular cavities in the fusebox" it must be my english which pins of the relay do you mean to cross?

When you say start do you mean crank? I meant to put a bridge in the fusebox instead of the starter relay's contact(terminals 30 - 87, attached) they might be shown on the relay , (for me 30 - 87 are perpendicular and 85 - 86 parallel ) if it cranks forget about that but if it doesnt crank on ignition but it will crank with the bridged relay we'll speak then

U are a Hero! I have connected 30 and 87 and the starter fires. When I put the ignition in position 2 and brigde theese terminal the engine starts and keeps on running. When I turn the ignition key to postion crank the white-red cable shows 12 volt, fuse 23 shows 12 volt on both sides so in the passanger compartiment the signal fro crank is comming through. I don't know for if it comes into the engine bay fusebox don't knowwhere to measure.

what would be next.

I somehow get the idea that the earthpath from the relay is not made back to the BCU, or the signal form the passenger compartment fuse box does not connect to the fuseboc in the enginebay.. The BCU relay shows 11.9 volt when reading with my nanaocom

Am I close or barking up a wrong tree?

Yes, you are on the good track, the relay's coil must get ignition feed on terminal 85 and earth from the BCU on 86, i suspect that it doesnt get the earth from the BCU for some reason, do you have RAVE cos you'll need the connector views from it then i'll tell you how to fix this

Good we are on the right track then.
If you mean by rave the electronic diagrams and connector details and all the other manuals, yes I do have a lot of manuals

Then see what's missing to trigger the relay in cavities 85 -86 while you turn ignition to crank, the feed or the earth just to be sure where to look