Im going to remove the CJB and see if its got any signs of corrosion. Does anyone know if the CJB is coded to the vehicle or can it be replaced with another i.e. 'plug n play', or does it need to be matched/programmed?

 

Are you testing for voltage without actuating the component? I don’t believe you would get energy across without actuating the peice. Just as a thought.

 

CJB is VIN specific.

have you tried to change the actuator as s diagnostic step?

 

Well I have the CJB out and there are no signs of any water leak or corrosion and my sunroof drain is also ok, so that rules out any change of the CJB having water get into it.

I have also realised the two FETs that control the tailgate are internal to the CJB, so there is basically pretty much no way to test them with the equipment I have, as I don't want to risk damaging the CJB if I get things wrong.

So back to the drawing board.

BTW is did test the upper actuator and it works perfectly well with 12V applied. I've also tested the lower tailgate switch and that works fine, but am still perplexed as to why both pins on the lower switch wire harness show a ground, one should in theory be open circuit to ground and the circuit is closed by the switch. With the being a ground reading (zero ohms to the batt neg terminal), the circuit would be activated constantly and the actuators would at least be in a permanent energized condition, but there is zero voltage reaching any of the actuators for either the upper of lower tailgate - very confused! All I can come up with at this point is there may be two issues, one the return line on the switch has somehow shorted to earth (work or rubbed against the chassis somewhere and the signal to activate both the FETs is dead, but even that is on two lines I think, but can't be sure as I have no internal circuit diagram for the CJB.

I think I need to look with fresh eyes in the morning.

BTW I found a great youtube vid for removing the lower glove box and the CJB.

Also the video to open the lower tailgate without there being power to the actuators

 

I’m going to sound like a broken record, did you try a new actuator?

I had a vehicle with an actuator code.

i removed the actuator and supplied 12 Volts on the bench and it worked, but not in the vehicle.

replaced the actuator with a new unit, all good.

 

Well I have figured it out - more by luck that anything, but I'll get to that in a moment.

I checked all the fuses, I even went to the length of splicing in a new return wire back to the CJB for the lower gate switch release due to the constant ground - which should not be there unless the switch is pressed. As soon as I removed connector C586 on the back of the CJB which has the return line for the lower switch release, the ground disappeared. This led me to believe I was facing a possible internal short in the CJB circuitry (NOOOOOOO!!!!!).

I rechecked each of the actuators for correct operation and they all worked as expected with 12V applied. I know Abran suggested this, but based on them all working with 12V and none getting 12V, they were in my eye all ok.

The actual fault!!

I thought, no wait, think about this logically, what are the symptoms. A strange ground and no power at all but the fuse is ok. Next, this is a Landrover with the most obscure logic in its electronic system design and I know that a fault in one system can effect something else totally and seemingly unconnected. so after checking all the fuses and then connectors to the CJB were seated fully, what else. Check all other connections I can find and that's when I found it. Under the driver seat towards the outside edge there is a grey connector with around 2 wires, a thick black and purple and a thinner black and purple and the connector looked to not be fully seated. I pushed it and 'click'. Guess what colour the power lines to the actuators are - yep, the same.

I then went to the back and pressed the release - bzzzzzzz, click - the actuators worked.

So this was simply a case that for some reason a connector that may never have been fully seated and finally came apart or someone in the past was doing something and they never fully seated it, regardless everything is all working. I have no idea why the constant ground was caused by this disconnected plug and at this point I really don't care

Thanks for all who commented, now I have to spend the rest of the afternoon putting everything back together, but I am very glad its all working again.

 

Well I have the same issue but my connector under the drivers seat is fine, so my question is; are you left hand or right hand drive?

 

Mine is a left hand

 

The upper tailgate was intermittently not opening. Just finished replacing the actuator, thinking it was going bad. Same problem. Sometimes the tailgate opens, other times nothing happens. No click, no motor sound. The upper switch might work eight times in a row, then nothing. It must be the switch.

If you repeatedly depress the switch, this applies to both the upper and lower tailgate switches for me, the click sound gets progressively weaker and eventually stops working. Is this a built in feature to prevent battery drain or indicative of bad switches?

To clarify: by 'switch' I mean the upper tailgate handle and lower tailgate button. Not actuators.