Circuit Description
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that module's Node Alive message. Each module on the class 2 serial data circuit which is powered and performing functions that require detection of a communications malfunction is required to send a Node Alive message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a DTC U1xxx where xxx is equal to the 3-digit identification number is set.
The control module ID number list below provides a method for determining which module is not communicating. A module with a class 2 serial data circuit malfunction or which loses power during the current ignition cycle will have a Loss of Communication DTC set by other modules that depend on information from that failed module. The modules that can communicate will set a DTC indicating the module that can not communicate.
| Control Module | ID Number |
|---|---|
| Powertrain Control Module (PCM) | 016 |
| Transfer Case Shift Control Module (TCSCM) | 026 |
| Electronic Brake Control Module (EBCM) | 040 |
| Electronic Suspension Control (ESC) Module | 057 |
| Body Control Module (BCM) | 064 |
| Inflatable Restraint Sensing and Diagnostic Module (SDM) | 088 |
| Instrument Panel Cluster (IPC) | 096 |
| Radio | 128 |
| Digital Radio Receiver (DRR) | 137 |
| Vehicle Communications Interface Module (VCIM) | 151 |
| HVAC Control Module | 152 |
| Driver Door Module (DDM) | 160 |
| Passenger Door Module (PDM) | 161 |
| Memory Seat Module (MSM) - Driver | 166 |
| Rear Seat Audio (RSA) Control | 167 |
When more than one Loss of Communication DTC is set in either one module or in several modules, diagnose the DTCs in the following order:
- Current DTCs before history DTCs unless told otherwise in the diagnostic table.
- The DTC which is reported the most times.
- From the lowest number DTC to the highest number DTC.