body control module bcm location

[bucket28]

Hi there, have the dreaded no bus on instrument cluster, scanned with launch x431 loads of communication faults in all the low speed bus modules with no communication with instrument cluster, carried out self test on cluster all ok. trying to check wiring between cluster and bcm but can't find it anywhere! its probably staring right at me but would someone be so kind and tell me where
Many thanks
Don

[Simon@thecustom300cshop]

Try disconnecting unplugging the headlamp module behind the R/H headlight (bolted to bracket on the inner wing near the washer bottle neck).

If its a CRD check the wiring harness has not rubbed through the the air con pipes beside the engine.

[UK CHRYSLER 300C]

I've never heard of the "dreaded no bus on instruments" on our cars

[jackwalton]

Think Chrysler change their terminology a lot.
Think they sometimes call the Body Control Module a Front Control Module. Fuse 6 in some of the earlier 300C's fed the Front Control Module, but I think the FCM is relates to Petrol vehicles. Have you checked all the fuses ?.

Jack

[bucket28]

Thanks for the help guys should have said it is a crd. Checked the wiring simon but couldn't fault it, and to UK CHRYSLER it is definitely ' dreaded 'when you've been working on it for nearly 4 hours :-). There is a fcm bolted to under bonnet fusebox jack and checked all fuses a couple of times, a feel I'm missing something simple, customer parked up one night next morning exterior lights are on permanently when started and instrument cluster has all lights on with no Rev counter no stereo or wipers. Any other problem areas for bus faults is very much appreciated

Thanks again
Don

[Simon@thecustom300cshop]

Originally Posted by bucket28

Thanks for the help guys should have said it is a crd. Checked the wiring simon but couldn't fault it, and to UK CHRYSLER it is definitely ' dreaded 'when you've been working on it for nearly 4 hours :-). There is a fcm bolted to under bonnet fusebox jack and checked all fuses a couple of times, a feel I'm missing something simple, customer parked up one night next morning exterior lights are on permanently when started and instrument cluster has all lights on with no Rev counter no stereo or wipers. Any other problem areas for bus faults is very much appreciated

Thanks again
Don

Did you try disconnecting the headlight module I mentioned earlier? The problems you mention now are exactly what happens when that module fails and disconnecting it normally cures it.

[bucket28]

Sorry simon didn't realise you meant to leave disconnected, I had checked connection on multi plug and wiring but did not leave disconnected will try when I get in to work in morning
Thanks again

[Simon@thecustom300cshop]

Originally Posted by bucket28

Sorry simon didn't realise you meant to leave disconnected, I had checked connection on multi plug and wiring but did not leave disconnected will try when I get in to work in morning
Thanks again

BTW, The headlights will still work with it disconnected

[jackwalton]

Could well be a single module dragging the CAN BUS signal down. Well worth disconnecting the lighting module as suggested.

If the above doesn't fix it I think the only way would be to refer to diagram, disconnect modules from ECM one at a time until BUS signal returns, (BUS would be best checked with an oscilloscope but can be done with a DVM, or poss. just rechecking for error codes ?). As you appreciate though, really time consuming.

Hope the lighting module fixes it. It is know to fail and affect the BUS and affect starting.
Think could get a diagram of all modules on BUS and connections if you need one but would take a bit of digging out.

From what I recall, the CAN BUS connections read about 2.4V DC on a DVM on both the "High" and the "Low" to chassis. Obviously this is not a signal measurement, just a means of checking for obvious faults or shorts to chassis. But obviously to check this you need a wiring diagram anyway to find the connection/module details.

Good Luck.
Jack

[bucket28]

Hi all again, simon I had high hopes this morning but guess what its still the same, tried disconnecting battery to reset lasts for about 5 secs then all lights back on. If someone is able too supply a wiring diagram i would be eternally grateful or even know I link to one.
Thanks for everyone's input so far

Don