Circuit Operation
Modules connected to the Class 2 serial data circuit monitor for serial
data communication during normal vehicle operation. Operation and commands are exchanged
among the modules. Connecting a scan tool to the DLC allows communication with the
modules for diagnostic purposes.
Diagnostic trouble codes (DTCs) may be set due to this symptom and during this
diagnostic procedure. Complete the diagnostic procedure in order to ensure all the
DTCs are diagnosed and cleared from memory.
Diagnostic Aids
| • | The body control module (BCM) detects that the ignition switch is ON and
sends the appropriate power mode message to the other modules connected to the Class 2
serial data circuit. The BCM must be connected to the Class 2 serial data circuit
for many other modules to communicate with the scan tool. |
| • | If the Class 2 serial data circuit was shorted to B+, a history
DTC U1301 will set in all modules except the auto climate control module. The
auto climate control module set DTC U1305. Refer to DTC U1301 or DTC U1305. |
| • | If the Class 2 serial data circuit was shorted to ground a history
DTC U1300 will set in all modules except the auto climate control module. The
auto climate control module set DTC U1305. Refer to DTC U1300 or DTC U1305. |
| • | If the malfunction is intermittent check for poor connections at the suspect
module. Wiggling harness wiring may help in locating the fault. |
