Bottom Tailgate won't unlock...Curious one this....

Was alerted by the girlfriend that the lower tailgate section won't unlock on the press of the button...

Thinking switch, fuse or relay...simples I thought!

The L322 tailgate locking system is operated thus....

The Upper tailgate is unlocked via the BCU, the release switch instructs the BCU to ground the Upper Lock Motor allowing it to run and unlatch.

Once the upper tailgate is unlatched, the BCU monitors the lower tailgate button and when pressed, the BCU grounds the coil of Relay 8. One of the switch pins on Relay 8 gets positive feed from Fuse 16 of the rear fuse box and the other switch pin is connected to the lock motors...the motors are then connected to earth via the local Earth stud.

So when the BCU pulls in Relay 8 it sends power to the lock motors to actuate the latch...

Now......

Here is what is happening on mine....Press the lower tailgate button and nothing happens and the relay doesn't click.

Checked power to fuse 16 - good
Continuity across lower tailgate switch - good
Power to the switch side of Relay 8 - good
Power to coil side of Relay 8 - good
Bridge switch side of relay - locks cycle

So it would seem the BCU isn't getting the unlock signal from the switch....BUT....

On the L322, the interior lights go out after a set time to save the battery.....if you press the lower tailgate button, the interior lights re-illuminate and the Sat Nav cycles just like it would if you were opening the doors or indeed the tailgate sections....so the BCU is getting a signal from the switch and is responding to it...it is just not pulling in Relay 8.

This could be a physical break in the wire from the BCU to the coil side of Relay 8 (unlikely) or the BCU doesn't know the upper tailgate is unlatched (plausible) but on opening the upper tailgate the interior lights illuminate and go out when it is closed again...also, there is no mislock or warning the tailgate is open...so I can only assume the BCU is happy with the upper tailgate...

Love to be able to plug in diagnostics but of course as you all well know, I am having major issues connecting via diagnostics at present!

In the interim, I have wired a switch bridging the relay switch pins so I can manually cycle the locks to release the lower tailgate as trying to use the emergency release levers is a pain in the backside!

Any thoughts or has anyone experienced this previously!

(And before the P38/Anti-L322 brigade pipe up about the overly complex arrangement and ridiculous amount of electrickery nonsense in the L322....we have heard it all before, it is called progress - without which we would never have left the primordial soup.....also I own a P38 as well so your comments mean nothing to me!! )

Have you tried switching it off and back on again?

The accessory Land Rover forgot to fit to the L322.

(And before the P38/Anti-L322 brigade pipe up about the overly complex arrangement and ridiculous amount of electrickery nonsense in the L322....we have heard it all before, it is called progress - without which we would never have left the primordial soup.....also I own a P38 as well so your comments mean nothing to me!! )[/quote]

Not going down that road Saint but do you really think it's progress Could say you are in the primordial sh1t but I won't. Good luck.

ant maybe a battery disconnection/reset will solve it

wil2813 said:

ant maybe a battery disconnection/reset will solve it

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Once we have been out today I will give this a try this evening on our return and report back.

Could all be bits dying from your HIDeous explosion, in which case it will be the BCU. I hope not.

Datatek said:

Could all be bits dying from your HIDeous explosion, in which case it will be the BCU. I hope not.

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I hope not too....

The Locks are a hardwired system so shouldn't be affected by any issues on the potentially corrupted K bus, that being said the BCU does communicate on the K bus with the Instrument pack, I am hoping this is not the start of other system failures...

Next step on the diagnostic mystery is to unplug the instrument pack and reconnect see if that does anything...doubtful as disconnecting the battery for 30 minutes did nowt, but it is worth a go...following that is to get another instrument pack and try that!

Sh1t what a fault!!

All I can off wi wishing you good luck on that one!!

Body control modules on early models are known to suffer issues

Saint.V8 said:

I hope not too....

The Locks are a hardwired system so shouldn't be affected by any issues on the potentially corrupted K bus, that being said the BCU does communicate on the K bus with the Instrument pack, I am hoping this is not the start of other system failures...

Next step on the diagnostic mystery is to unplug the instrument pack and reconnect see if that does anything...doubtful as disconnecting the battery for 30 minutes did nowt, but it is worth a go...following that is to get another instrument pack and try that!

Click to expand...

Flog the car - get another L322.

StuckAgainSteve said:

Flog the car - get another L322.

Click to expand...

Flog the L322 get another P38

Saint.V8 said:

(And before the P38/Anti-L322 brigade pipe up about the overly complex arrangement and ridiculous amount of electrickery nonsense in the L322....we have heard it all before, it is called progress - without which we would never have left the primordial soup.....also I own a P38 as well so your comments mean nothing to me!! )

Click to expand...

Progress is to make things better, not more complex and worse. Keep it simple stupid.

Given the amount of electrical issues you've been having in quick succession, I would imagine you have a much larger electrical problem that is masking itself as smaller niggles. I'd put money on the light popping being the first symptom, not the cause.

Does the boot latch work in isolation or does it share with any other circuits, e.g. interior light, other locks, petrol cap release?

I was wondering if one of the others had a break or had chafed and was touching to earth somewhere. If the BCU is looking for a difference and both circuits are high or both low then the BCU wouldn't know to switch it, if you follow me? Although in that case I'd expect something else not to work too. A lot of ifs in there but I have no idea how it works other than there's electronics in there and they're a nightmare to troubleshoot!

Grrrrrr said:

Does the boot latch work in isolation or does it share with any other circuits, e.g. interior light, other locks, petrol cap release?

I was wondering if one of the others had a break or had chafed and was touching to earth somewhere. If the BCU is looking for a difference and both circuits are high or both low then the BCU wouldn't know to switch it, if you follow me? Although in that case I'd expect something else not to work too. A lot of ifs in there but I have no idea how it works other than there's electronics in there and they're a nightmare to troubleshoot!

Click to expand...

Thanks for the ideas, but on the L322 all the systems are pretty much separate and very rarely do they share the same circuits or fuse/supply.

Worth looking for chaffed wires though, seems like the BCU isn't grounding Relay 8 coil to switch the locks, so maybe there is lack of continuity from BCU to rear fuse box!