Disco 4 (LR4) Tailgate intermittently won’t open - fixed

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guineafowl21

Well-Known Member
Posts
3,352
Location
Inverness
2010 model. It’s the top door affected.

Plenty of threads on here about it, and as a result I’ve found the following:

The keyfob button doesn’t work either; sometimes a double beep is heard.
Sometimes, switching ignition off and on and waiting will resolve it temporarily.
The lock release actuator looks fine, and there is no 12V pulse to it during the fault.
If I leave the ignition on for a short while, a ‘low battery - start engine’ message sometimes appears.

This, for me, rules out the door microswitch and the actuator. The battery was fitted 2018 and the car is used daily, so I can’t see it being that.

My iCarsoft LR V2.0 has just bricked itself, although less than two years old, so I can’t read codes at the moment. Any thoughts on the problem, and recommendations for a scan tool that isn’t crap would be appreciated.
 
guineafowl21 said:
If I leave the ignition on for a short while, a ‘low battery - start engine’ message sometimes appears.
Click to expand...

If the low battery warning comes on after a short time, then it battery isn't any good.

The locking issue seems strange, so it's worth checking the connections at the CJB.
 
Nodge68 said:
If the low battery warning comes on after a short time, then it battery isn't any good.
Click to expand...

lynall said:
Tried spare fob?
Are the fob batteries okay?
Click to expand...

Car battery fitted 2018 so I hope it’s not goosed.

Tried both fobs, same result. One has a new battery.

I occasionally get a ‘smart key not found’ message on getting in the car, even though it starts fine. Lots of silly behaviour like this could add up to a duff main battery, I suppose.

@Lazydave the ‘add quote’ has stopped working, but I don’t think it’s the door switch because the fob button doesn’t work either.
 
guineafowl21 said:
Car battery fitted 2018 so I hope it’s not goosed.

Tried both fobs, same result. One has a new battery.

I occasionally get a ‘smart key not found’ message on getting in the car, even though it starts fine. Lots of silly behaviour like this could add up to a duff main battery, I suppose.

@Lazydave the ‘add quote’ has stopped working, but I don’t think it’s the door switch because the fob button doesn’t work either.
Click to expand...


My 2019 fitted battery is starting to show its age, leave car for more than a couple of days and it is not to keen on starting.
This will be the third battery in 6 plus years, I do lots of short journeys which is a real killer but also normally trickle charge it once a week or so, but since wife has been off work I have not been able to get to the plug socket.
I am not sure on the D4 but if you google discovery 3 wiring splice failure passenger side, have a read and see if the 4 is the same?
 
I’m now the proud owner of a GAP IID BT.

Problem is still there. According to the IID app, the boot switch input goes ‘on’ when the switch is pressed, and the output also goes ‘on’ although the solenoid doesn’t always activate. This suggests to me something downstream of the ECU, perhaps a relay? Does anyone know where it is?

On the control I/O bit of the app, I can sometimes activate the tailgate solenoid, although not always.

Occasionally, the ‘tailgate open’ warning appears on the car screen, even when it’s shut. Does anyone know where the sensor for this is?
 
guineafowl21 said:
Thanks. The only thing against that is that I found no 12V pulse to the actuator during the fault.
Click to expand...


Ah okay.

Are you using a multimeter or a lightbulb?

Have you checked in the rubber trunking between top of door and the body for broken wires etc? not seen it on a disco but see it a lot at work.
 
lynall said:
Ah okay.

Are you using a multimeter or a lightbulb?

Have you checked in the rubber trunking between top of door and the body for broken wires etc? not seen it on a disco but see it a lot at work.
Click to expand...
I think I used a multimeter and an incandescent test light.

I’ll check the rubber trunking - a simple thing I should have checked first!
 
guineafowl21 said:
I think I used a multimeter and an incandescent test light.

I’ll check the rubber trunking - a simple thing I should have checked first!
Click to expand...


Multimeter might tell you that you are seeing 12+ volts, but it means diddly squat, you need something to pull the power, and this is where a bulb and two wires comes into play.
Might be worth seeing if you can find a wiring diagram for the rear set up, I could be wrong but think its pretty simple, ie you pull handle/button and this sends power to the actuator?
 
I spent about 5 hours on this yesterday with test light, multimeter, and GapIID.

The actuator has permanent ground, ie is power-side switched. During the fault, no 12V appears on its connector.

I traced the switched power wire to a large loom and there is no break in the wire.

The ‘open tailgate’ signal seems to come straight from the BCM, from a FET inside. There is no external fuse or relay in the signal line.

Trying the key to open the boot often results in two beeps, but no opening. Sometimes it works. Sometimes I get ‘smart key battery low’ error message. It’s not low, it’s brand new.

According to GAP IID:
1. The ‘tailgate ajar’ sensor works 100%.
2. The ‘open tailgate’ microswitch works 100%.
3. The BCM reports a pulse to the actuator every time the microswitch is pressed, but no 12V arrives.
4. Using control I/O, I can sometimes force the actuator to open, sometimes not.

This suggests:
1. It’s not the door switch.
2. It’s not the actuator.
3. It’s not a fuse or relay.
4. It’s not the smart key batteries, which are both brand new Panasonics.

This smells to me like the BCM playing silly buggers. It could also be tied in to the ‘low battery’, ‘smart key not found’, and the two beeps I get when attempting to open the boot via key button.

Options:
1. Soft reset using GAPIID.
2. Hard reset by disconnecting battery for 10 mins, then shorting cables.
3. Re-flash BCM with update (there is one available, apparently). Please explain how - I’m frightened.
4. Change vehicle battery.
5. Re-learn keys?

Can anyone suggest a suitable order of business?
 
I would be inclined to do a hard reset first. If that doesn't do it and the main battery is not 100% replace the battery. D3/4's are sensitive to battery condition as are Range Rovers. What voltage does your battery show across the terminals when measured first thing in the morning before you try to start it?

I'm not sure re-flashing the BCM is the answer. Unless there is good reason GAP recommend leaving ecu's alone. HTH
 
classic kev said:
What voltage does your battery show across the terminals when measured first thing in the morning before you try to start it?
Click to expand...

Thank you. I don’t know what the voltage is early morning, and the wife is using it today.

If I leave the ignition on for just a few minutes, the ‘low battery start engine’ reliably appears. Battery fitted Dec 2018 (PO helpfully wrote on it) which I would consider brand new - my Def Td5 battery lasted 16 years.

I realise these Discos are a different beast, however. Here’s the plan:

1. Obtain new, decent battery and smart charge it.
2. Ignition off, wait 120s, then disconnect old battery, as per the warning label.
3. Wait 10 min, then short battery cables.
4. Install new battery.
5. Use GAP IID to recalibrate battery monitoring, for which I might need some advice.

Any good?
 
I'm not 100% but doesn't the D4 have a AGM battery?? Worth checking as the characteristics are different to a normal wet type battery, something to do with re-charge time and max CCA output. The age of a battery is not necessarily or automatically the best indicator of health; my last car, the main battery lasted 10 years or so, the auxiliary battery gave up at 10 years so I replaced both but that was on a Mercedes. On my RRC I have been using a Numax battery which is designed for deep discharge because I rarely use it. I have just replaced that battery after 11 years.

Your 2018 battery is nearly 3 years old. D4's, like D3's have a high electrical demand and if the car is not in regular use or only does lots of short hops and stop/start driving you will kill the battery in surprisingly short order. Do check the battery voltage first thing in the morning, this should give you some idea. I am fairly sure that somewhere there is a thread that explains what voltage you should be looking for, maybe try a search in the Range Rover section, you'll get the idea.
 
My battery is on its way out just three years old, though I am hard on it wiith lots of short trips, its a Yuasa 019 silver top.
The previous one only made 18mths, dont buy an exide 1000ca one as they are pants!
I think even with a new battery the system is very marginal, with little room for error/lights left on etc before you get a non start situtation.

Recent post on d3 forum where guy said his battery was 8 yrs old, and this was considered by most to be some sort of record.

If doing anyhting with the IID it is wise to have a trickle charger connected.
 
I would recommend the Enduroline battery fitted to my Def Td5 - 3 years of short journeys, winch operation, left for months on end once and it still kicked the engine round like it was on the motorway yesterday. Brilliant.
 
guineafowl21 said:
1. Obtain new, decent battery and smart charge it.
2. Ignition off, wait 120s, then disconnect old battery, as per the warning label.
3. Wait 10 min, then short battery cables.
4. Install new battery.
5. Use GAP IID to recalibrate battery monitoring, for which I might need some advice.
Click to expand...

Done this (except step 5) and the problem is still there. At least I’ve ruled out battery problems.

So I know the ‘open’ signal gets to the BCM, but the pulse to the actuator doesn’t always arrive. Wiring is good from the tailgate back to about halfway to the BCM.

Next thing would be to obtain a pinout of the BCM (which I assume is part of the passenger side fusebox?) and see if the pulse is reliably there at the connector. Then address the BCM if it isn’t there, and the wiring downstream if it is.

Can anyone point me to a BCM pinout?

@gstuart I seem to remember you had some diagrams - can you help?
 
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