P38A Boot Switch

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Bix

Bix

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1999 Range Rover P38 Derv

Howdy, howdy, howdy,

Since binning the Merc the RR has decided that it is going to start throwing it's toys out of the pram.
The boot switch has stopped functioning, now checking online I saw if the drivers lock doesn't function correctly, that is the problem, but what is correct functionality?

When I tried to unlock it after being parked overnight, the key only turned the drivers door and not anything else, but if I use the key after cycling the locks on the fob, the central locking functions as expected. Is this normal as the car is asleep or should the central locking always function?

As for the tailgate, I assumed power going into the switch is always live (when unlocked, obviously), but when using my test light I saw no signs of power, I would use a multimeter, but mine has packed in. Again, is this normal or is it just a telltale that the drivers door switch (CDL?) is faulty?

Thanks for your time,
Bix
 
Afaik the cdl should operate at all times regardless of unlocking on fob or key.

The power to the boot switch is a low voltage signal to/from the BeCM all it does is tell the BeCM that you pressed the switch to open the boot. The BeCM then powers the lock solenoid to open the latch.

The BeCM will ignore the switch input if the CDL hasnt been triggered from the fob or key input.

If your system isnt cycling the CDL you won't be able to open the boot as the BeCM doesn't know if it should.

Hope that makes sense.

Might pay to look at the latch and the woring thereto first.
 
So I would assume that means my CDL is potentially faulty then?

I've had the carpet off and playing with the connector it started working again, so I put it down to a loose plug. But no fiddling back there seems to do anything now. Bridging the switch doesn't cycle the actuator so I am guessing the fault is from the front of the vehicle? But on that end, I saw the actuator is ground by the CDL, so would it not receive constant live? So if I introduced a new ground it should at least operate to rule out that as the problem?
 
Saint.V8 said:
Afaik the cdl should operate at all times regardless of unlocking on fob or key.

The power to the boot switch is a low voltage signal to/from the BeCM all it does is tell the BeCM that you pressed the switch to open the boot. The BeCM then powers the lock solenoid to open the latch.

The BeCM will ignore the switch input if the CDL hasnt been triggered from the fob or key input.

If your system isnt cycling the CDL you won't be able to open the boot as the BeCM doesn't know if it should.

Hope that makes sense.

Might pay to look at the latch and the woring thereto first.
Click to expand...

You're mostly correct :)
Yes, the CDL switch is active at all times - it will change state whether the latch/door is locked with the key, fob, or the sill lock button.

However, unlike the front doors the tailgate latch doesn't run through the BECM at all (surprisingly!) it gets power from there, but that's about it (other than the 'tailgate open' switch, which alerts the BECM when the latch is opened (but not locked/unlocked))

The tailgate latch is permanently powered off fuse F15 from the BECM fuse box (along with a load of other things). The power then goes to the motor in the actuator. The ground for the motor then (from memory) goes through the tailgate switch, and then to the CDL switch in the RHF door. So if the RHF door is unlocked (CDL switch grounded) then there is a ground path there for the tailgate motor, when the button is pressed - which will then obviously drive the actuator and pop the tailgate. Pressing again will then pop the bottom half.

If the CDL is faulty and not grounding, then the BECM won't know if the door is locked/unlocked (it will constantly think it's in one state... usually locked (open circuit) is how it fails... and it will also mean there is no ground path for the tailgate actuator, and this will stop it from unlocking - as Saint.V8 says - but for a slightly different reason, as it's a direct connection, rather than the BECM doing the

Bix said:
So I would assume that means my CDL is potentially faulty then?

I've had the carpet off and playing with the connector it started working again, so I put it down to a loose plug. But no fiddling back there seems to do anything now. Bridging the switch doesn't cycle the actuator so I am guessing the fault is from the front of the vehicle? But on that end, I saw the actuator is ground by the CDL, so would it not receive constant live? So if I introduced a new ground it should at least operate to rule out that as the problem?
Click to expand...

I would say that either the switch has actually failed now (they do corrode out sometimes) or the CDL in the door latch has failed, so there is no ground path when the door is unlocked, so the tailgate is effectively permanently 'locked'
If you grounded the wire coming out of the switch, then if it isn't the switch or power feed to the actuator which is faulty, then yes, the tailgate should then unlock.

If that's the case, I would look at replacing the door latch - I've had a couple of owners now who have obviously had this issue, and then found that the previous owner had wired in an extra ground wire into the tailgate, so the tailgate was then affectively permanently unlocked... which happened to also mess with the rest of the central locking system. (might have been on this forum actually)

It's worth whipping the door card off and using the test sheet to see what's happening with the drivers door latch (if anything) If that all checks out, then I'd be looking for a damaged wire on either the power/ground to the dash switch..

Hope this helps,

Marty
 
martyuk said:
You're mostly correct :)
Yes, the CDL switch is active at all times - it will change state whether the latch/door is locked with the key, fob, or the sill lock button.

However, unlike the front doors the tailgate latch doesn't run through the BECM at all (surprisingly!) it gets power from there, but that's about it (other than the 'tailgate open' switch, which alerts the BECM when the latch is opened (but not locked/unlocked))

The tailgate latch is permanently powered off fuse F15 from the BECM fuse box (along with a load of other things). The power then goes to the motor in the actuator. The ground for the motor then (from memory) goes through the tailgate switch, and then to the CDL switch in the RHF door. So if the RHF door is unlocked (CDL switch grounded) then there is a ground path there for the tailgate motor, when the button is pressed - which will then obviously drive the actuator and pop the tailgate. Pressing again will then pop the bottom half.

If the CDL is faulty and not grounding, then the BECM won't know if the door is locked/unlocked (it will constantly think it's in one state... usually locked (open circuit) is how it fails... and it will also mean there is no ground path for the tailgate actuator, and this will stop it from unlocking - as Saint.V8 says - but for a slightly different reason, as it's a direct connection, rather than the BECM doing the



I would say that either the switch has actually failed now (they do corrode out sometimes) or the CDL in the door latch has failed, so there is no ground path when the door is unlocked, so the tailgate is effectively permanently 'locked'
If you grounded the wire coming out of the switch, then if it isn't the switch or power feed to the actuator which is faulty, then yes, the tailgate should then unlock.

If that's the case, I would look at replacing the door latch - I've had a couple of owners now who have obviously had this issue, and then found that the previous owner had wired in an extra ground wire into the tailgate, so the tailgate was then affectively permanently unlocked... which happened to also mess with the rest of the central locking system. (might have been on this forum actually)

It's worth whipping the door card off and using the test sheet to see what's happening with the drivers door latch (if anything) If that all checks out, then I'd be looking for a damaged wire on either the power/ground to the dash switch..

Hope this helps,

Marty
Click to expand...
Thanks for the information and sorry for a slow reply. I finally got the bus in the workshop.

I am a bit rusty on electrics, but it seems I have power, but when I earth the actuator it doesn't cycle (reading 12v from the negative side so power is going through). From what I understand, that suggests it is the actuator that is faulty as it should still cycle, correct?

Thanks.

[edit: Took the plug off the actuator and bridged it with my multi-meter, pressed the boot switch and it started showing 12v. So I'm going with the actuator has failed. Now to find a part Land Rover no longer manufacture or supply. Push comes to shove I'll have to get an eBay special.]
 
Last edited:
If you get 12V across the actuator plug with the button pressed, then it sounds like the motor in the actuator has failed alright.
In your other test by grounding the other side of the actuator, and then nothing happening, then it pretty much confirms is.

I think you would be OK with an eBay special on the actuator to be honest - they are not known for having a high failure rate! Usually it's the door latch or more precisely the microswitch in the door latch that fails causing tailgate opening problems...
 
I had the same problem, it was the connectors on the motor. I twisted them slightly with a pair of pliers,and it has worked for the last two years. worth checking.
 
martyuk said:
If you get 12V across the actuator plug with the button pressed, then it sounds like the motor in the actuator has failed alright.
In your other test by grounding the other side of the actuator, and then nothing happening, then it pretty much confirms is.

I think you would be OK with an eBay special on the actuator to be honest - they are not known for having a high failure rate! Usually it's the door latch or more precisely the microswitch in the door latch that fails causing tailgate opening problems...
Click to expand...
Rodger, I suppose for 20ish quid, it is no real hardship if it doesn't last. Cheers.

tarphenry said:
I had the same problem, it was the connectors on the motor. I twisted them slightly with a pair of pliers,and it has worked for the last two years. worth checking.
Click to expand...
Connectors on the motor? You mean where the multiplug goes? If so I have a solid connect to them as power flows in and out. Or are there different connectors on the motor that I can access by stripping it?
 
On mine the motor plugged into its housing with 2 little brass flat pins. it was these that were not connecting properly
 
tarphenry said:
On mine the motor plugged into its housing with 2 little brass flat pins. it was these that were not connecting properly
Click to expand...
Well how about that? Just popped open the actuator, cleaned down the contacts and refitted it. Seems to have done it. In the morning I'm going to add a strip of heatproof double sided tape just so the lid offers more compression as the pins seemed like they've worn somewhat over the years. I'll test it out and see how I get on. Going to order an eBay part anyway, so if it pops again I have a backup ready to go.

Thanks, it has been a ballache not having a fully function tailgate.
 
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