U1192

CIRCUIT DESCRIPTION




During normal vehicle operation modules connected to the class 2 serial data circuit monitor the class 2 serial data circuit for serial data communications. Operating information and commands are exchanged among the modules. When a module receives a critical operating parameter message, the module records and learns the identification number of the transmitting module for the purpose State of Health monitoring. A critical operating parameter is one which, when not received, requires that the receiving module use a default value for that parameter. Once an identification number is learned by a module, it will monitor the class 2 serial data circuit for that module's Node Alive message. Each module on the class 2 serial data circuit is required to send a Node Alive message every 2 seconds. If no message is detected from a learned identification number for 5 seconds, a DTC U1xxx, where xxx is equal to the three digit identification number is set.

CONDITIONS FOR RUNNING THE DTC
^ The following diagnostic trouble codes do not have a current status:
- B1327
- B1328
- B1982
- B1983
- U1300
- U1301
- U1305
^ The vehicle power mode requires serial data communication to occur.

CONDITIONS FOR SETTING THE DTC
A message from a learned identification number has not been detected for the past 5 seconds.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC will clear when a Node Alive message from the failed identification number is detected on the class 2 serial data circuit or at the end of the current ignition cycle.
^ A history DTC will clear after 50 ignition cycles.

DIAGNOSTIC AIDS
When multiple Loss of Communication DTCs are set concurrently, the cause is likely to be two opens in the class 2 serial data circuit. Use the Control Module ID Number list in order to determine which modules are not communicating. Use the class 2 serial data circuit schematic in order to determine the location of the opens.

TEST DESCRIPTION

Steps 1-11:

The numbers below refer to the step numbers on the diagnostic table.
1. DTCs U1161, U1162, U1163, and U1170 indicate a malfunction in the power door serial data circuit.
5. The following modules have a single wire connection to the class 2 serial data circuit. An open in the single wire will prevent communications.
^ Cellular Telephone Module
^ Driver Door Module (DDM)
^ Memory Seat Module (MSM)
^ Navigation Data Processor
^ Steering Column Module
^ Vehicle Interface Unit (VIU)
8. The module which was not communicating due to an open in the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.
10. The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.