Accessing BCM

[Tander]

Wiper module (J400) and alarm siren (H12) are on neighbouring pins on the same BCM plug (Pins T46b 30 and 31 respectively) which is the smaller middle plug, for when you gain access to the BCM.

Side note, it helps if you have the hands of a 10 year old girl to get decent finger access to the plugs LOL

As above, the BCM holds Component Protection (CP), key data for remote central locking and controls a whole host of things on the car which some likely won't work properly without the correct parameters loaded. Genuine ODIS with authorised online access is your best friend for this.

I am not familiar with OBD11 (and it's ilk) but if it has similar functions and features as VCDS then I'd check the output from the wiper stalk and try and trigger the wipers from the diagnostic tool just to confirm everything outside of the wiper motor is correct as it's a 10 second job and adds verification that the problem is the motor end.

I'd also test for power at pin1 (Red/White wire) on the plug at the wiper motor end of the loom. Even though the "No Comms" fault codes are pretty solid lines of investigation to follow, always best to cover all avenues before parts swapping.

Thanks for the help.

How difficult is it to get to the BCM to have a look at the plugs you mentioned?
Outside air temp is reporting its 41c - obviously wrong. Is that related I wonder to the BCM?

OBD11 has some output tests I can do, the app wan't £70 for the privilege of doing such things, which is a bit steep.

At the moment, my options are:

1. Buy a single channel scope and hope its a cable somewhere obvious
2. Strip interior to get to BCM and hope its something obvious and not a dead BCM
3. Leave it and take it to the garage on Saturday for them to diagnose and resolve (They're doing an oil change, too)

The OB11 tool doesn't give live data for the stalk position.

 

[cairus]

The OB11 tool doesn't give live data for the stalk position.

Wrong.

If you have Control unit 16, you need the live Data from unit 16

 

[Tander]

Wrong.

If you have Control unit 16, you need the live Data from unit 16

Oh okay must have missed this. I’ll go check again. Thank you.

 

[Craig.]

Thanks for the help.

How difficult is it to get to the BCM to have a look at the plugs you mentioned?
Outside air temp is reporting its 41c - obviously wrong. Is that related I wonder to the BCM?

OBD11 has some output tests I can do, the app wan't £70 for the privilege of doing such things, which is a bit steep.

At the moment, my options are:

1. Buy a single channel scope and hope its a cable somewhere obvious
2. Strip interior to get to BCM and hope its something obvious and not a dead BCM
3. Leave it and take it to the garage on Saturday for them to diagnose and resolve (They're doing an oil change, too)

The OB11 tool doesn't give live data for the stalk position.

I always take off the sill trim, footwell trim along with the whole glovebox out to get to the BCM as it makes things easier, including getting to the plugs visually.

The BCM is blocked in place until all 3 plugs are disconnected and there is also a tab that secures the BCM in place. Once the plugs are out and tab pushed up then the BCM can slide out with some encouragement.

I'd advise disconnecting your battery first.

 

[Craig.]

Outside air temp is reporting its 41c - obviously wrong. Is that related I wonder to the BCM?

If it's G17 Ambient Temp sensor then that is pin 27 on the same T46b BCM plug as your Alarm horn and wipers and only 3 pins over from the wipers so it's looking fairly likely that you have corrosion on the central BCM plug

 

[Tander]

If it's G17 Ambient Temp sensor then that is pin 27 on the same T46b BCM plug as your Alarm horn and wipers and only 3 pins over from the wipers so it's looking fairly likely that you have corrosion on the central BCM plug

It’s looking that way it seems. I’m going to go have a go at getting this bcm out. Seems to be the pain central point of failure.

Would the bcm need replacing?

 

[Tander]

I always take off the sill trim, footwell trim along with the whole glovebox out to get to the BCM as it makes things easier, including getting to the plugs visually.

The BCM is blocked in place until all 3 plugs are disconnected and there is also a tab that secures the BCM in place. Once the plugs are out and tab pushed up then the BCM can slide out with some encouragement.

I'd advise disconnecting your battery first.

Appreciate the help

I’ll grab some electrical contact cleaner and pull the BCM out on Friday morning to see if cleaning it will resolve it and see how it got wet to begin with.

 

[Craig.]

It’s looking that way it seems. I’m going to go have a go at getting this bcm out. Seems to be the pain central point of failure.

Would the bcm need replacing?

If the damage to the BCM is significant then yes

 

[Tander]

If the damage to the BCM is significant then yes

Guess only one way to find out. I’ll pull it, clean the area and plug with contact cleaner and then clear codes and see what happens afterwards.

If I do need to replace the BCM - I guess it’s dealership only then really. I doubt local garage will have the special tools to do it.

 

[Craig.]

Guess only one way to find out. I’ll pull it, clean the area and plug with contact cleaner and then clear codes and see what happens afterwards.

If I do need to replace the BCM - I guess it’s dealership only then really. I doubt local garage will have the special tools to do it.

Main dealer if you intend to get a brand new one, they won't do a used unit.

I'd look locally for an independent VW Group specialist as there are many dotted all over the UK that have legitimate ODIS access with online authorisation.

 

[East Yorkshire Retrofits]

Main dealer if you intend to get a brand new one, they won't do a used unit.

I'd look locally for an independent VW Group specialist as there are many dotted all over the UK that have legitimate ODIS access with online authorisation.

Worth noting many independents won’t fit customer supplied used BCMs (especially facelift as the VIN can’t be read from them prior to starting the process)

We only install new or we can supply used sourced from a trusted supplier