RRS - Upper Tailgate Unlocking on Start

[101RRS]

Jumped in the RRS this morning and started and there was a rattle in the back. Drove off and then noticed the tailgate open message was on the display. I arrived at the shops car park and closed the upper tailgate and locked the car.

On coming back to the car and on starting I heard the upper tailgate unlock and then the message appeared. On testing, the upper tailgate is unlocking by itself just after the engine fires - not when the ignition is turned on and not when the starter is engaged but just as the engine fires.

Any clues on what might be causing this - it is only the top tailgate that unlocks and sometimes you can hear the servo trying to lock the tailgate without success.

I suppose like all things on these vehicles every function is unnecessarily controlled by a computer - I will try a hard reset when the rain stops but am interested to hear if anyone else has had similar issues.

Thanks

Garry

[gghaggis]

Is your key FOB button set to unlock the upper or lower tailgate? You might try using the other key.

Cheers,

Gordon

[101RRS]

Is your key FOB button set to unlock the upper or lower tailgate? You might try using the other key.

Cheers,

Gordon

Already thought of that - one key is set for the tailgate and the other for headlights on, so tried both keys and it does it with both. :(

Thanks

Garry

[101RRS]

The RRS UK forum suggested that the upper tailgate latch could have corrosion so causing the problem.

I have had a good look at this today - the actual switch seems OK and even with the switch disconnected the actual lock disconnects up to 60 secs after engine start. There is an electrical pulse coming through the system unlocking the upper tailgate between 1 and 60 secs after engine start.

I removed the actual lock and removed the little electric motor - with only the electric motor connected it runs for about 1.5 secs up to 60 secs after engine start so it is the car that is telling the lock to unlock. I did a hard reset of the car's computers with no change. I read the codes and found two general electrical faults and signal faults. I cleared these and then recycled the tailgate lock and started the engine - the fault came back but no fault codes were logged in the system.

So at this time I am at a loss what the issue is. I tried closing the top tailgate and disconnecting it at the connector with the intention of just using the complete tailgate but disconnecting the top tailgate electrically also disables the bottom tailgate so no access to the cargo area.

Ideally I would like to try a new lock but there is no where I can get access to one without buying one ($120), so not prepared to do that just yet in case it does not fix the issue.

Other ideas would be appreciated.

Garry

[Graeme]

Already thought of that - one key is set for the tailgate and the other for headlights on, so tried both keys and it does it with both.Have you tried the other fob?

[Graeme]

I have had a good look at this today - the actual switch seems OK and even with the switch disconnected the actual lock disconnects up to 60 secs after engine start. There is an electrical pulse coming through the system unlocking the upper tailgate between 1 and 60 secs after engine start.....
Ideally I would like to try a new lock...As it happens with the switch disconnected, a different lock wont help.

[101RRS]

As it happens with the switch disconnected, a different lock wont help.

Don't quite follow. The UK site indicated that that the switch can get corrosion in it and cause the issue but if the lock is removed from the circuit and the latch still opens when a pulse comes from the car maybe the latch is faulty and responds in the incorrect manner when the computer sends a pulse through on/after start.

That is the other aspect that has me baffled is to why the car sends a pulse through on start to up to 60 secs after start. It is not to test if the door is open as there is another way of doing that I have not sussed - with the latch closed and the hatch open the tailgate open message does pop up.

All very confusing - looks like I will have to do what the stealers do and that is replace parts one by one and then find that it is not a hardware issue but a software issue but still charge the client for the not needed parts.

I did ask the dealer yesterday if I could try a new latch first but the response was "you try you buy".

Garry

[Fitzy2011]

My vehicle is setup for all the doors to lock once it gets up to a couple of klms an hr, is it possible it is trying to lock with all the other doors and is opening instead?? Just a wild guess!!

[sniegy]

Sounds like something is shorting to earth, causing the lid to open. Check the wiring in the tailgate lids & see how goes it!

[Graeme]

Don't quite follow. The UK site indicated that that the switch can get corrosion in it and cause the issue but if the lock is removed from the circuit and the latch still opens when a pulse comes from the car maybe the latch is faulty and responds in the incorrect manner when the computer sends a pulse through on/after start.
The switch provides an earth path on a wire from the bcu. If the switch is corroded then the wire could provide a sufficient path through the corrosion but if the switch is removed then no earth path is possible.
The lock motor has only a single power and an earth wire indicating that the motor only unlocks rather than both locks and unlocks. The switch does not interact with the lock itself, only the bcu.

Can you currently use the unlock switch?

[Graeme]

... and sometimes you can hear the servo trying to lock the tailgate without success.
When can this noise be heard? By my reckoning the servo only opens (not locks/unlocks) so is it actually trying to open at other times?

[sniegy]

Graeme on the lower section of the Sport(not early MY's tho') tail gate they have a motor that, to a point, auto closes (or pulls the tail gate closed) & maybe that's what Gary can hear?

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[101RRS]

My vehicle is setup for all the doors to lock once it gets up to a couple of klms an hr, is it possible it is trying to lock with all the other doors and is opening instead?? Just a wild guess!!

No the car does not have to be moving for the rear upper tailgate to unlock- my car is not set up for auto locking at the moment.

On this line I have found a way to stop the rear gate unlocking - when the ignition is turned on but the engine not started if you lock the doors via the switch on the dash the rear door does not unlock even when the doors are unlocked via the dash switch.

Doesn't fix the issue but makes it livable.

Garry

[Graeme]

Graeme on the lower section of the Sport(not early MY's tho') tail gate they have a motor that, to a point, auto closes (or pulls the tail gate closed) & maybe that's what Gary can hear?IIRC Garry's is an early one.

[101RRS]

When can this noise be heard? By my reckoning the servo only opens (not locks/unlocks) so is it actually trying to open at other times?

When the door has unlocked it then continues to continue to try to unlock itself at intermittent intervals. But as I indicated above if I have locked the doors via the dash switch the tailgate door does not unlock at all.

Garry

[Graeme]

Does the glass open using the switch? If not or only sometimes then that could indicate a short further up the wire towards the BCU.

[Graeme]

But as I indicated above if I have locked the doors via the dash switch the tailgate door does not unlock at all.That's a standard feature so that no-one can open the back when stopped in traffic.

[101RRS]

Graeme on the lower section of the Sport(not early MY's tho') tail gate they have a motor that, to a point, auto closes (or pulls the tail gate closed) & maybe that's what Gary can hear?

Sent from my iPad using Forum Runner

No it is the top latch - I pulled the little motor out of it and can see the motor running at intermittent intervals for about a second or so each time - the pulse to run the motor is coming from somewhere but not sure if this is a result of the relevant computer not getting getting correct signal back or is just a stray pulse being generated by the system - can happen up to 60 secs after start.

[Graeme]

Its looking to me to be a short in the harness from the top door. I expect there's a connector just inside the rear somewhere (LHS?) from which the switch wire (pink with slate trace if same as early D3) can be removed to confirm or disprove the short. The D3 has 2 connectors between the switch and the bcu with the wire in pin 7 of one and pin 20 of the one closer to the BCU.

[101RRS]

Does the glass open using the switch? If not or only sometimes then that could indicate a short further up the wire towards the BCU.

The upper tailgate opens by the fitted latch or the key fob as it is supposed to - it does stay closed when pushed closed when the engine is off but just does not stay closed when the engine fires up. With the engine then running the rear upper door can be closed and sometimes it stays latched and some times it doesn't.

Also today when it has stayed latched and the engine is switched off it has started unlatching itself but when relatched it stays latched until the engine is started.

It is all so confusing and is starting to do my head in :confused:

[Graeme]

the pulse to run the motor is coming from somewhere but not sure if this is a result of the relevant computer not getting getting correct signal back or is just a stray pulse being generated by the systemThe power to the motor is switched using a FET within the BCU. It uses a very simple electrical setup so something is telling the BCU to open the glass (most likely the switch wire) - it wont be a stray pulse.

[101RRS]

In pulling the rear door trim off, I noted that unlike just about all other panels on these cars you just do not pull it off - some manipulation is required - I just pulled it off so bits of broken plastic went flying everywhere :(.

I did find a sub woofer in the back door - I have the mid range radio and I did not think it had a sub woofer which I thought was only in the top range radio. If I do have a sub woofer, do I have a amp to drive it or is it just driven by the radio.

Garry

[Graeme]

Garry you're keen at this time of night!

I have no idea about your speakers but vibration from the engine starting and idling could be causing the switch wire with worn-through insulation to momentarily touch the bodywork, perhaps at the spots where the wiring exits the door frame or enters the body. Even just manipulating the rubber shroud might cause it to continually operate the motor or fix it for the moment.

[101RRS]

Thanks Graeme - while I do not think that is the issue I will check it out. Interestingly when the doors are locked I do not have the issue. I will also take the unlock function out of the main key fob as I assume it changes the programming in the relevant section of the computer - again I don't think it will fix anything but is worth a try.

No fault codes are now showing up.

If the issue is still there next week I will do just what the dealer will do and start replacing parts.:(

Thanks to everyone for your input - looks like no one has had this locally and the one in the UK was fixed by replacing the latch switch which I don't believe is my issue.

Thanks

Garry

[Graeme]

If there is an intermitant short in the wiring between the switch and the bcu then connecting a voltmeter across the switch terminals with the engine idling should show the voltage (either 5V or 12V) momentarily dropping to zero.

[101RRS]

Thanks Graeme - I will put the multimeter on it tomorrow and see what it does.

Oh - the fault code is back. B1C42 - Tailgate Release Switch 2 - Signal Failure - Signal Stays Low.

Does anyone have detailed information on this.

cheers

GARRY

[Graeme]

Signal staying low is indicating a connection to ground somewhere, as though someone is holding the switch for an excessive time. The signal is "high" when at its 5V or 12V (whichever is used) then pulled low to earth by operating the switch.

[101RRS]

Well I will be ..........

After a week with this problem I went out to the car to do the checks suggested by Graeme and to trace some cables to see if there was anywhere where they may have been chaffed and creating shorts.

I started the car and there was no unlocking of the rear tailgate - I switched off and restarted 10 times and no issue - so I went for a drive and no opening of the rear tailgate :confused:.

I am not going to put the trim back just yet but it would seem that after a week the problem has just gone away.

I am beginning to think that these cars have a mind all of their own:(.

Edit - could this issue be caused by low voltage in the battery?? The only reason I raise this is that the radio did show low power a couple of times, the cables to the switches etc in the tailgate are very small and and at the far end of the car and the fault codes did show voltage low. The radio is no longer showing low power so the battery must be back up.

Garry

[sniegy]

Garry,
I do not think that low battery will have an effect on the tail gate opening. It needs to be switched. Otherwise there would be tail gates opening everywhere in winter!

Just by removing the trim may have relieved the pressure on a wire shorting to earth.

Check all the wires in the tailgate, it is time consuming but worth it.
Also check & see the wiring in the roof at the rear, there are a bunch of multiplugs just above the roof lining & one could be under pressure.

Cheers & Good luck.

Sent from my iPad using Forum Runner

[101RRS]

I agree symptoms do seem the be related to something shorting or leaking voltage somewhere.

I am now thinking water in the system somewhere. When the problem started it had been raining for a few days and the car had been parked outside, now that the weather has stopped raining and the humidity low the issue has gone leading me to think that some crucial spot got a little damp. The switch was damp but with it disconnected the problem still continued.

Power for the system comes from the Central Junction Box and may be the culprit if it can be exposed to moisture. So where is this CJB so I check it for corrosion/moisture.

Thanks

Garry

[Graeme]

From the fuse numbering I assume that the CJB is part of the passenger compartment fuse panel.

The switch wire only needs to carry half a milliamp so probably is only as thick as it is so that it doesn't break.

[sniegy]

Behind the lower glove box is where the CJB is located.

Garry does your beast have a sunroof?

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[101RRS]

No sunroof, so if it is in the cabin in front of the glove box it is not likely to get water in there so if it comes back (which it will because I have put all the trim back in) i will have to look elsewhere.

Garry