Symptoms Of Faulty Wake-Up Communication Line

An open in a communication line will cause most systems to not operate because one multiplex control unit cannot wake up other multiplex control units. Multiplex control units that are not awake will wake up when a related switch is operated. Turning ignition switch to ON position will wake up all multiplex control units. If a communication line is shorted to ground:

• Most of the systems do not operate because one of the control units will not wake up the other control units.
• Control unit can wake up by a related switch operation, but other control units cannot wake up by a switch operation.
• All control units wake up by turning ignition switch to ON position.