P38A Another question regarding Central Locking problems!

Hey Guys,
I'm newly registered here but I've been using the site for a while now to look through all the old posts to help me with a few problems I have with my 1997 (R reg) P38 4.6L HSE.

One of the many problems I have is that the Right Front Door lock (Front Driver's Side) doesn't lock the central locking either by the key in lock from the outside or by pushing the lock button on the door from the inside.

If I do do the same from the front passenger side then both front and rear doors are locked. Its then only the tailgate that doesn't lock.

My key fobs don't work but I'm thinking as the batteries went flat they will need to be re-synchronised, and from what I have been reading it seems that can only be done in the drivers door lock?

I took the door card off to inspect/test the door actuator and someone has already been in there before me as the foam covering has been gaffa taped back up. They had also unplugged the smaller connector with the one black wire in it. (My actuator is the 2 plug type as its a early P38). When I plugged the smaller connecter back in and turned the ignition back on, I then got a "ALARM FAULT" message appear on the dash.

Am I right to think the actuator needs to replaced as although it works when a signal is sent from the passenger door, it will not work when activated from itself??

I would like to add that the motor starts and drives fine, but I would like to get the central locking working as I get worried leaving the tailgate unlocked when I park up in the for the evening.

Thanks in advance for your suggestions.

@martyuk is your man when it comes to door locks hopfully he will be along soon, but it the micro switches in the lock need looking at Marty has done test sheet for testing.

That sounds great!
I hate it when something "half works". If there was no life at all, I would be a lot more confident with thinking it needs replacing!
Thanks for the reply.

That smaller plug with the black wire is the earth, I think. Either way it needs to be in there for the actuator to work. What is a complete mystery to me is why it would trigger an alarm fault message.

Usually the problem you state would be the microswitches on the bottom of the actuator. Think Brian is right and Marty is the man to understand this!

CDL switch on drivers door mech is duff. May just need cleaning or maybe knackered.

Thanks for the replies.
I've posted a message to Marty's profile.
Just to let everyone else know, I did the tests Marty mentions in a article he wrote and I found out the following.
The CDL "sill button up" test came back with a open circuit rather than a closed circuit.
The CDL motor test came back with a reading of 45ohms rather than 4-20ohms as Marty suggests.
Therefore I'm 99% sure the actuator is faulty and will need replacing.
Hopefully Marty can help me out, as otherwise I will have the annoying task of ringing all the breakers.

Here is a photo of the problematic actuator!

Looks very dry and rusty, you could try a bit of penitrating oil but it sounds like a micro switch problem. Worth a try though.

After repairing my drivers door lock a few weeks ago, today it started showing door open again & mislock issue when locking the car.

Took the lock out. Reconnected and closed the latch with screwdriver, and it works. Seems the wear on the latch bar plus the slight wear on the lock internals mean the "door open" microswitch doesn't always trigger. Reassembled, and adjusted the lock position slightly in the door . . . . now it works again. Might also need the door pillar loop adjusting a 0.5mm or so, but not done that yet.

I suspect the microswitch is gonna need replacing soon, but working for now.

**UPDATE**
A new (second hand) lock is in the post to me today so hopefully by tomorrow the central locking will be working again!
Only the Alternator, A/C Condenser, Brake Discs and Head lining to repair/replace now!

**UPDATE""
I received my new latch (actuator), its fitted and.... I now have central locking again!
The only problem is my tailgate still doesn't lock
The upper and lower sections work fine on the button, and when its open the interior lights come on BUT I have noticed no warning message comes up on the dash when I attempt to drive with it open.
I've sent Marty a message to see if he knows the answer but I guessing there may be a micro switch that's faulty?
I'm 80% there now but I would love to have the entire central locking system working again!

Have you stripped the tailgate button ? It's worth a look at.

As the button works to open the uppers and lower sections of the tailgate I was thinking it must be in good order? .... As you say though, there is no harm in taking a look.

Check the linkage to the solenoid while you are in there. Just reread your post,if it's not the micro switch's then check the white block connector's behind the driver's side A post panel.

Do you know how to test the micro switch? If I'm given a dummy guide then I'm fine testing things (like with the post on the door actuator) but otherwise auto electrics are a headache for me.
Also what should I be looking for in the white connectors?
Thanks for all your advise.

EssexP38 said:

Do you know how to test the micro switch? If I'm given a dummy guide then I'm fine testing things (like with the post on the door actuator) but otherwise auto electrics are a headache for me.
Also what should I be looking for in the white connectors?
Thanks for all your advise.

Click to expand...

Corrosion on the contacts re the block's, you will have to check the micro switches with a multi meter but that will mean taking the door latch off again and checking the wiring via Rave. I would have a look at the block's first, the advice is to cut out the block's and solder/heat shrink the wire's.

I have been in contact with EssexP38 via PM about it, but will post this here aswell...

The microswitches from the door locks go to the outstation, which then get transferred to the BECM over a serial bus, so if some functions are working, then the wiring between the outstation and the BECM are fine.

The door wiring doesn't actually go through the infamous 'kick panel connectors' (though they are worth checking and cleaning anyway as a lot of other things do go through there!) but rather go through another set of connectors further up the A pillar, and can be accessed by pulling the rubber cable gland out from the body side, and the connectors hide in there. Again, worth giving them a clean.

Check the door latch following the same tests (don't worry too much about the CDL motor resistance - as long as it works! as that is more in the tests to see if it's open circuit, or short circuit (which would show up a faulty motor).

If the replacement door latch shows up as being fine - then I would investigate at the tailgate the wiring, and also the wiring in the door at the outstation that goes back to the tailgate. The tailgate motor grounds through the CDL switch - so if it is able ot be unlocked all the time, then this shows one of a few things:
a) the replacement latch has a faulty CDL, which is showing 'unlocked' all the time,
b) someone previously has found the front door latch is faulty, and permanently grounded the tailgate motor, so it can be opened.
c) the wire to the tailgate has somewhere been caught (possibly in the door) which is grounding the tailgate motor wire all the time, meaning it will be operate when it shouldn't be

There isn't much more to the tailgate circuit than that - it's powered from a fuse on the BECM, goes through the button and motor, and grounds though the CDL switch in RHF door latch. There's a separate microswitch in the tailgate latch with sends a signal to the BECM when the tailgate is open too.

Hope this helps narrow it down..

Marty