BCU fault diagnostic to a fault on 5volt - CAN lines

[nickchiz]

A warm hello to everyone, I have this fun fault and plunder with my Ford Custom 2014 2.2van. Ok.. so back ground, a couple of weeks ago my brake lamp on passenger side stop working with a dash error (this occurred when I put my foot on the brake), a couple of days after (before I looked to fix the bulb) the front dipped beam passenger side stopped working with a fault on the dash when I turn the dip on. After looking at the bulbs and connections, I couldn’t fix these two issues. I inspected the BCU unit as I was advised to look there for fuses and it had water on it, I disconnected it and could see the top plug had water damage not too exsmtreme but still had the powder white look. I have since shipped the unit off to a specialist and they have reported a fault with the unit, caused by a fault on the 5v CAN lines. They are repairing the unit as we speak, but has suggested there is a fault somewhere on this 5v Can line. I do wonder 1. If someone has any idea where I could look first? From Experiance of such fault. 2. Could this chip, of been damaged by the water damage arcing over the pins on the plug if the BCM?

Any help would be greatly appreciated.

[loot]

We call it the bcm(body control module) Fords name is the cjb(central junction box) I've seen a few posts on water ingress causing partial or complete failure, I think the remedy was a replacement module.

You should be able to buy a second hand unit and get it programmed in. That may need to be ford though. They may say no it needs to be new though.

You need ids with pats access

[nickchiz]

Hi Loot, thank you for your reply. Thanks for the correction of BCM name. It’s promising your thoughts are also pointing towards water ingress in the module (again). Not sure I put it into the original post, but 12 months ago the van was in with a mechanic with interior light staying on, dash turning on /off, heater witches off, windscreen wipers on off random times, umm and some other random stuff, the mechanic changed the BCU unit with a new one, this solved everything. He mentioned the error maybe due to water ingress, but didn’t say any more on it,
I did notice this time around that the BCM gets water dripping on it when we have long rain fall, this was when I took the dash out to see what was going on.
My biggest concerns are
1. If I start to try to go through testing the host looms 5v circuits as suggested by the Tech expert, will I just get stomped and possible cause more issues?
2. If I go with my (gut) or hope and it’s down to this water issue, then just replace this unit, it could just blow the chip again and I would be back at square one?

I have constructed a hood that will cover the BCM, to prevent fingers crossed water ingress.

Also, can anyone answer this query? If there is a fault somewhere on the 5V host system, then how /why /is there no fuse protecting the Brain of the van? (BCM), of power surges etc? Surely if the fault is outside the box and somewhere in the vehicle, and the 5v circuit get a 12v spike surely I should see a fuse somewhere on the van blown? Not a internal chip on the BCM.

Any guidelines would be greatly appreciated, and I apologise for such a long post ..

[loot]

Typically the bcm is well protected. To turn things on and off they work on ohms and ground switching for driver input control and then secondary output to items mostly 12v. The ground inputs shouldn't see a voltage, the powered outputs are fused... Water ingress directly on the bcm is the problem that if you've insulated it then great. In theory opening up the bcm and drying it out before the corrosion gets it may work. However if you've exhausted all other possibilities like the type socket etc then it may be quicker to swap the bcm to atleast diagnose it. I say that as opposed to popping to the main dealer for diagnostics and then new bcm etc as that is going to hurt a lot.

If your mechanic has already swapped it before then hopefully it won't be too costly.

[loot]

Typically the bcm is well protected. To turn things on and off they work on ohms and ground switching for driver input control and then secondary output to items mostly 12v. The ground inputs shouldn't see a voltage, the powered outputs are fused... Water ingress directly on the bcm is the problem that if you've insulated it then great. In theory opening up the bcm and drying it out before the corrosion gets it may work. However if you've exhausted all other possibilities like the type socket etc then it may be quicker to swap the bcm to atleast diagnose it. I say that as opposed to popping to the main dealer for diagnostics and then new bcm etc as that is going to hurt a lot.

If your mechanic has already swapped it before then hopefully it won't be too costly.

Can bus will turn off if sorted as too many error messages will make it. You will get fault codes for that.

But can is twisted pair of wires and only links modules so if the fault isn't at the bcm then it'll just turn off the module it is at.

Anyway try and get a full half code read and post up the codes here if you can.

[nickchiz]

Hi all, any help please, so my can still has this fault, I had the repaired BCM and fitted it hasn’t worked, I have tested the plug end of the dipped beam on the Lh that isn’t working and I get 4v. In attempt to revisit the original offending area I see, there is a Headlamp control module. Could this be my issue or am I looking in the completely wrong area?