Vehicle: 1999 Chrysler LHS, 3.5L, VIN G,
Problem: No communication with all control
Details: The fuel gauge became erratic, then a
“No Buss” message was displayed on the instrument cluster. When
this happened, scan tool communication was lost to all modules.
Cycling the key to KOEO restored communication to all modules
until the engine was started, and then the modules dropped off
again. Disconnecting the alternator restored communication. A
scope check revealed a 1.8 v ac ripple, indicating bad diodes.
The tech replaced the alternator but that didn’t fix the problem.
He also noted that with a battery charger connected, KOEO, the
problem also existed. Without the charger connected, there was no
Confirmed Repair: Looking at the wiring diagram,
the tech noted that all communication to the DLC Pin #2 goes
through the BCM then to all other modules. Replacing the BCM
solved all communication issues. Charging system voltage created
an open circuit in the BCM, which may have been previously
damaged by the bad alternator diodes.