Symptom: Loss of communication to a number of modules.
Cause: Individual control module has dragged down the K_BUS system or could also be a wiring fault.
- Are K_BUS faults stored in a number of control modules on your Autologic device?
- K_BUS faults stored. This is a 12v square wave signal. When the car sleeps this sits at 12v and when active this switches to square wave signal, 1v below battery voltage.
- Note down the modules with the K_BUS faults.
- Check for water ingress into the modules that have stored fault codes.
- Next find the buzz bar, which is located behind the glove box, with white/red stripes and yellow hoops. (see image here)
- Remove all cables from the buzz bar and find the wire that is generating the square wave signal.
- Relocate the cable generating the signal onto the buzz bar and systematically check all of the other wires to see if they are going to earth when the ignition is off
- If any are going to ground, mark it and tie it back before reconnecting all remaining cables to the buzz bar.
- Carry out a quick test to see if any control units are not communicating.
Note: to check cables you will need an oscilloscope.