BCU Fault?
 

Hi all,


Hoping you can help!


My ZT-T Diesel had been parked outside for a week or so during the snowy period. I knew the battery was not at peak condition before then, but it was still starting the car - just a little sluggishly.


I came to drive it after the snow and noticed when I unlocked it the indicators didn't flash as normal. I got in and tried to start it up. It did start up but was very lethargic at turning over and only just coughed into life. I also noticed that the A/C screen was really dim and all of the buttons reacted really lazily - imagine what you get if a calculator is almost flat - buttons take a second or two to react and makes the screen go almost off while it does the action.


I put it down to a naff battery so I took it off the car, charged it up overnight and refitted again next day. Car then started fine and A/C screen lights/buttons were all back to normal. However now I notice that the indicators don't show up as flashing on the dashboard or make the associated ticking noise, even though they are flashing outside.


Wondered if it was just a knackered battery (shorting internally or something odd) so I bought a brand new one and just fitted it. Initially the indicators flashed when I unlocked, and when I used the stalk on the steering column, but then they wouldn't turn off! Now they've stopped and have reverted to not coming back on again on the dash (but still working outside).



I've also noticed that none of the telltales light up on the dash even though they all work - main beam, indicators, front or rear fogs etc. It does think that there is a permanent door open which I assume it thinks is the bonnet, as the interior lights go off correctly when the passenger doors shut. Dash illumination works fine and I've run a full self-diagnostic sweep and everything works correctly (including the ticking of the indicators).



And now, to top it off, it will only unlock on the key fob. It will lock from the button between the front seats, but won't lock on the fob for some reason. I've tried clicking the unlock on the fob several times in quick succession but no cigar.


Does this sound like I've got a duff BCU? Is there anything I can check? Could a water-damaged ECU cause such stange behaviour? I'm fairly sure it won't be wet as I checked the plenums quite recently, but who knows with all the snow I suppose.


Any thoughts?! Cheers!

With a diesel i would always see if the ECU has had water ingress - the diesel ECU's are not sealed unlike the petrol ECU's and its easy to check for tidelines/corrosion/moisture etc and if all looks fine you can discount this.

I'll give the ECU plenum area a check tomorrow morning

Problem is now solved but I'll stick some info here which helped me, in the hope it can help someone else in the future.


Had a check of the ECU / plenum area - as I hoped (and expected) there was no sign of water ingress or flooding.


So , following some extensive late night reading, I came to the conclusion that it was a K-bus fault somewhere as the symptoms were all related to items on the K-bus.


I found this thread very helpful - specifically the last post from MGMarc which details a simple diagnosis test for each of the K-bus lines. My plan was to locate the connector in question (which was tucked quite high up behind the RH side of the lower dashboard - up and behind the light switch module), remove each wire in turn to see if the communications were restored, and then refer to the wiring diagrams on RAVE to determine which component was throwing the circuit out.


Due to the location of the connector on my wiring harness it was quite difficult to access without being a contortionist, so party due to laziness I thought I'd start with some of the connectors on the other ends of the K-bus lines. I haven't got a FBH (which would have been my first port of call), so my first stop was the CD changer in the boot.


I pulled off the little hatch in the boot and sure enough there was a pool of water with an unused connector sat in it, one wire of which was white/red/yellow (K-bus):duh: A quick dry off of the connector, and a disconnection of the CD changer entirely, and hey presto - all systems returned to normal.


My next stop would have been the seat connectors which are prone to corrosion and getting wet if the carpet under the seats are wet.


Next task is to figure out where all the water is getting in from!!

Congrats on your perseverance:bowdown:
Good luck with the boot leak:D