The BCM operates what is called the “X relay” which powers the circuits which have failed. Occasionally the BCM fails in its earth control line to the relay but the relay is usually the problem. The relay is on the front plate of the BCM which is under the drivers side dash above the drivers right lower leg and the relay is at position KL75 (B9) with the number 460 printed on top, VAG part number 1K0 951 253 A and there are two of these, the other is for the ignition. Swapping them over may pinpoint the fault but if the one at KL75 is faulty the lack of a KL15 signal will have the same effect. If you know what to do, bridge the two large terminal positions at KL75 and this will bring the circuit up even if the BCM or the relay is faulty.

 

Hi, thank you so much for getting back to .e. I did forget to add that the car will now not start at all, my son carried on driving it and when he came out of a shop he got nothing, won't even turn over, tried jumping still nothing, no lights on dash at all. But stereo still comes on and central locking still works.
It is currently stuck outside my friends house who was local to where it broke down.
Just went up and tried the disconnect battery, left lights on to drain circuit for 15 minutes then reconnected, that didn't work

 

I would suggest a new battery, sounds like that one has dropped a cell

 

Am in aa, so will give them a call, sneaky I know, but saves me forking out if it's that simple.

 

Am in aa

I could do with joining too… ohh you mean THE AA, I thought you meant… that reminds me, it’s gone 6pm.

If a cell has gone completely dead it will stop even a 2k booster pack like we use at work.

 

Was just thinking though, shouldn't it have turned over with a jump even if the cell was down?

 

Yes not alcoholics anonymous 🤣 I could do with being in that this time of year.
Have another good battery that I can try. Will take that up and give it a whirl tomorrow, will let you know what happens

 

Progress report so far,tried another good battery, no different.
Called AA after he did some tests, he was stumped, I suggested swapping the 2 460 relays over and boom it started.
I now just have to get another 460 relay tomorrow as I now know one is bad, fit that and it may bring the heater blower, washer motor and 12v socket back online.
Will keep you posted

 

Update.
Ordered bcm with same part number, swapped this out with the old one, still exactly the same, no heater fan, washer or 12v cigarette lighter.
Have loads of 460 relays now so tried swapping these out, no change.

 

Do the systems come up if you bridge the X relays two large socket positions?

 

Been a bit under the weather today, will try that tomorrow. So just bridge on 1 single x relay the 2 large terminals actually on the bcm from what you have said if I'm understanding correctly and just see if the systems come up.

 

The two large board slots corresponding to the relays 30 and 87 terminals. I would suggest using a fused bridge if you are unsure.

 

No that's what I thought, I would be ok doing that. Will do tomorrow and update.
Thanks for all this help and guidance I do really appreciate it.

 

Take care, the 30 terminal is fused but it is something like 100amp so can make a mess.

 

Ok pal will do

 

Hi mate
Bridged the relay today between the terminals, didn't bring anything back up to life.

 

So from that it determines that it is not the bcm or the relay that is at fault from what we were discussing. Is that correct

 

The terminal on the relay labelled 30 should have power to it, do you have a test light or multimeter?

 

Yes I have a multimeter will test that for power tomorrow.

 

Hi crasher
Got a mate who is a sparky to help me with all the multimeter tests so I knew it would all be spot on.
So no power to terminal 30 on relay with ignition on or off.
Also he tested fuse 33 40 amp inside car, fusebox below bcm, which he thinks is the fuse that feeds it.
Fuse was fine, but no feed getting to fuse with ignition on or off.

 

Current update, all sorted Crasher, thank you so much for your help.
So finally got to the bottom of it, the original cause was the faulty 460 relay, which I never knew.
I took to a local reputable garage and they charged me £180 to tell me the fuses and relays were fine, presumably they just checked engine bay relays as it didn't look like they had taken das apart to access bcm. They just told me that it indicated a faulty bcm, which I changed, still same fault.
It turned out that they had replaced one of the 50 amp fuses back in the wrong location in the engine bay fusebox, I put it back to the right position, hey presto all systems back up.

 

What vehicle is this?