Central Locking woes

[maelgwn]

Hoping you guys can help me out with some troubleshooting here ...

For 6 months + neither of the remotes for my central locking have worked. Started out just one not working - tried changing the battery with no luck and after a period of occasionally needing two tries to work, the second one stopped completely as well. Had to unlock with the key in the door.

Scan of the car gives error code 00470 - Combination comfort Databus in single wire mode. Sporadic 011 - open circuit.

Basically it means there is a dodgy connection/wire somewhere in the comfort Can Bus. However the comfort can bus is supposed to work with only one wire, so not convinced this is the cause of the problem?

And today, I noticed the central locking with the key is not working properly. Locking the car with the key does not lock the back doors (left nor right) but locks the front and boot ok. Pressing the lock button inside the car locks everything ok.

Where should I look next? How do I find the mystery wire problem?

Thanks in advance

Edit: its a 2005 mk5 1.9tdi golf

[vdubmotorworx]

dont worry about the single wire mode fault it makes no difference to the operation.. the convienence CAN can work on only one . it has 2 wires so it has a back up but as its not a saftey system ie airbag etc it will continue to work ok... is there no faults for any of the door locks?. i would get one new remote.. code it up and test from there...VDUB...

[maelgwn]

dont worry about the single wire mode fault it makes no difference to the operation.. the convienence CAN can work on only one . it has 2 wires so it has a back up but as its not a saftey system ie airbag etc it will continue to work ok... is there no faults for any of the door locks?. i would get one new remote.. code it up and test from there...VDUB...

No faults on the door locks - but I only have a cheap scanner, do they sometimes miss things?

And neither of the rear doors work - meaning unlikely to be a fault in the door but somewhere further up in the system I would think?

[vdubmotorworx]

yeh some scanners so miss stuff. doors locks are common on golf 5. but usually the doors are locked and cant be opened when they fault..

[vdubmotorworx]

i would still get a remote working first then see if you have a rear door fault after that. start with that... get the car unlocking via a remote and then recheck whats happening....VDUB...

[Idle]

That one remote failed before the other suggests that the batteries may be low, so my first move would be to change one — they're cheap (CR2023, from memory) readily available on the 'net and from computer shops and not difficult to DIY.

The locking fault could be due to a faulty wire where the cables pass from pillar to door usually the driver's door, which gets the most use.)
It's a well-documented problem, as also are failing MkV door locks.

[maelgwn]

Well - I finally looked into this some more.

The automotive locksmith said that the remote seemed to work ok (generate a signal and be readable by the car) but he couldn't program it. Tried a new remote and it worked ok, so now I have a new remote.

However it still doesn't lock the back doors.

So, symptoms now are:

Front doors and boot now unlock and lock fine with the remote, key in the door and drivers button.

Back doors unlock fine with the remote, key in the door and drivers button however they DO NOT lock with the remote or the key in the door. They do lock with the drivers button.

When tested through the comfort module, front doors and boot lock ok, however the test stops at the back left door - no response from the lock actuator on this door. Because the test stops it does not try to lock the right side back door.

Does anyone know any differences in how the drivers button works compared to the remote locking? Does the drivers button send a different signal than the Comfort Control Module when locking the car?

[AALocksmiths]

Hi Maelgwn,

I have had time to have a quick look into it. The fault code was coming up in the central electrics control module as well as the back door modules. It was odd that the remotes would unlock the doors but not lock them and the Lock/ Unlock on the drivers door would work them fine.

The fault code looks like it could be related from anything that talks on the CAN network as well as a damaged wire, as you know that the doors work I think it would unlikely be a wire. I'm leaning more towards the Central electrics module.

I haven't pulled one apart (Yet) so I'm not 100% sure on how it works but I'm thinking that the rear doors would work as one output, I think that it would be this which is not working. It could be from either a damaged component on the PCB, corrosion or dry solders, I have found the dry solders to be common in VAG cars so this is where I would be starting.

One way that you can try narrow this down is to unplug the CECM from the CAN and see if the fault goes away.

[maelgwn]

I haven't pulled one apart (Yet) so I'm not 100% sure on how it works but I'm thinking that the rear doors would work as one output, I think that it would be this which is not working. It could be from either a damaged component on the PCB, corrosion or dry solders, I have found the dry solders to be common in VAG cars so this is where I would be starting.

One way that you can try narrow this down is to unplug the CECM from the CAN and see if the fault goes away.

Thanks

I'm assuming you mean the Comfort Control Module?

I pulled it out and pulled it apart a while ago and there was not anything obviously wrong with it. I'm not the most experienced with this stuff but it looked fine.

When the CCM was disconnected nothing further was revealed by scanning - from memory the error was then something like Comfort Canbus Open Circuit, instead of single wire mode.

[AALocksmiths]

No, not the comfort module.

The CECM from what I have read should be above the peddles and has a couple of relays sticking into it.

I have been looking into what functions can be changed in each module and both the Comfort and the CECM have options for the door locks, so this might be why the back doors lock from the switch on the drivers door but not the remote.

I don't think that with your car the modules are coded to the car so you might be able to get both computers from a wreck and swap them over to see if that fixes it, they will most likely need to have the functions coded but that's not an issue. The other option is to remove both modules and check all the solders and connections. If you wanted I can help you out with that.

I will keep looking into it though to see which parts each module play with the locking and unlocking of the doors as that will help narrow it down.