'04 ISX Volvo Multiplexing dead

Been there done that, its actually the first thing I did. The strange thing is the CAN is perfectly fine, 60 Ohm, no shorts, power supply fine to all modules, and grounds are fine. Did the ECM swap last week with same codes intermittant. This has to be a short in the 400-401 wiring, finding the bad wire is another story when there is 400ft of it in the cab alone.

 

Can't read codes from cluster except "engine" ecu, all else dead, fuel pedal not responding at all, but 1937 is ok.
Yes : Swapped engine ECM, and replaced VECU, from volvo truck with multiplexing. parameters set properly and all else good.

cut out the CAN from diagnostic link 9 pin connector, connected cummins insite, still showing same codes. I think this tells me it a J1587 issue. However I can't figure out why the CAN isn't working. The J1587 will only transmit diagnostic information if the CAN fails to transmit diagnostic information or is this wrong?

I am about to replace the CAN completely, Even though it has tested ok I have to start eliminating all possible causes.

 

After replacing some questionable wire connectors in the EECU harness at firewall I decided to disable some multiplexing functions in the EECU parameters, disable/check for codes, kept this up until I set "Idle Validation" to disabled causing J1939 Multiplexing fault to go completely inactive, and it stayed inactive until I enabled it.


Checking circuit now... stay tuned

 

Found broken "looks cut" wire #567-c under fuse panel, repaired wire and found the relay it was going to was bad, replaced relay and now circuit functioning perfectly, this relay was for engine management circuit. I'm very happy this is over with, truck revv's up like a champ.

Now I have to figure out why there is no light signal to trailer light-cord, and no brake lights in both trailer-cord and truck.
Also the vehicle speed sensor keeps acting up, had it working fine yesterday when I installed a new sensor, tried it today and again sensor is dead. 3rd bloody sensor in this thing in last 2 months. Something must be shorting it out.

Later in the night: found VSS wire shorting on bottom of cab where the bodybuilder harness goes into floor of cab, repaired and now that problem is fixed.

Truck brake lights fixed as well, removed all weather-pack terminals in harness which were loose and corroded.

Trailer cord another story, I'm thinking the LCM is NOT powering the relays to the cord.
MID216, PSID53, FMI6
MID216, PSID51, FMI4
MID216, PSID12, FMI4

12AM: Power to relays ok, but no signal voltage.
Checking grounds now... stay tuned

2AM: GOING TO WENDY'S FOR A BACONATOR!

 

Found interior ground for trailer cord not properly grounding, by-passed ground circuit to new ground on frame, also noticed auxilliary circuit for trailer cord not being switched by LCM properly, by-passed this as well, everything working perfect!

Would like to thank Thetruckersreport.com for allowing me to post this information, hopefully if someone has similar issues the posts I have contributed will help them.