Okay current codes, at the power steering control module U2107, U2105. At the instrument panel cluster U2129. I also have a U2100 being displayed at the power steering module but it's saying it's passed.

 

Tech Feature: Update on CAN Diagnostics
Good read. last few paragraphs caught my eye. Im gonna try unplugging the power steering module. And see if the EBCM will communicate with steering module unplugged. Maybe the the power steering module finally called it quits.

 

try it and see what happens.


120 ohms means one of the bus lines is open.



if the codes are in the power steering module, the p/s module is communicating.
the modules that sets the code has lost communication with the non-functioning module. You can't get codes from the non functioning module as you can't communicate with it. So the module you should disconnect is the ebcm.


it still may not start if the bad module is removed but there are checks that can be done to locate the open

 

The plan is to unplug the EBCM and jump the bus lines on the connector and see if I get the ohms back into spec. any idea where i could find a pinout for the ebcm connector?

 

try it unplugged first. the jumper wires could work but must be the exact same length and resistance. any difference will corrupt the voltage timing as the high and low bus signals must be insync.


I'll look for a pinout


if it doesn't work I can go thru the easy way to pinpoint the open.

 

no change with the ebcm disconnected

 

does the vehicle have onstar?


-disconnect the neg bat cable
-make sure all modules except the ebcm are plugged in
-at the ebcm connector, put your ohm meter across pins 37 tan and pin 36 tan/blk...what you get?
-then put the leads across pins 22 tan and pin 21 tan/blk...what you get?

 

Yes I believe so. Im looking for a pinout diagram for the connector so I know which pins are which.

 

on pins 21-22 im getting 123 ohms
cant get a reading for 36-37

 

what you did was split the system in half. We now know the side that ohmed 120 is all good. the open wiring/bad module is somewhere in the other half.


the daisy chain runs in this order...from the dlc to the psm, to the bcm to thevcim to the ebcm
the problem is in that half of the bus








next we go to the next module and do the same thing and repeat until the open leg is found. reconnect the ebcm and unplug the vcim

the pins for the oher modules are


vcim pins 2, 3 then 8, 9
bcm- which contains one of the 120 ohm terminating resistors. connector c2 pins 1, 19 and 2, 20

power steering module pins 4, 5 and 1, 2
dlc -where you first started pins 14, 6



post the results