BCM Fault

[Motormouth]

Hi Everyone,

Recently I keep getting a stop/start error on my van intermittently.

Checking with vag com I have the usual BCM no communication fault 25796.

I don’t have any other fault codes relating to the alternator.

Today I have checked the yellow/green lin wire from where it connects to the battery to alternator and it seems fine, less than 1ohm resistance and doesn’t alter when cable moved. The next thing I could check is from the BCM to the battery.

I’m trying to understand what this fault actually means then I may be able to look at electrical diagrams and fault find. So does anyone know what this fault actually means? Does it specifically relate to the battery charging as I thought the BCM controlled a lot more than just the charging of the battery.

I think the van has had a new battery recently before I bought it but not sure if it was coded after fitting. I presume this couldn’t cause this fault as it is intermittent.

Screenshot of fault code.

Any help much appreciated.

 

[Vedubber]

I had a start / stop error for ages, which never threw up an actual fault code of any sort.

Turned out it was the battery control sensor on the negative terminal. Replaced it and everything was back up and running.

 

[Motormouth]

Thank you for your reply.

The fault code I have and the start/stop might not be related. That is why I wondered if anybody knows what the fault code is actually relating to.

To me BCM no communication could be communication with many things but not sure?

How much was the part?

 

[Motormouth]

I’ve decided to remove the battery to charge it fully then refit and tell the van it’s had a new battery. Not sure if this will sort the stop start fault but worth a try. I don’t think the battery is very old but I don’t know if the van was told it had a new battery fitted. The code starts 075 and it is a 80ah battery.

Once I do this is there anything else to do except change the code for the battery?

Does anyone know what voltage I should get on the lin cable if I disconnect it at the battery and test it to earth there.