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.
Control Module | ID Number |
|---|---|
Powertrain Control Module (PCM) | 016 |
Electronic Brake Control Module (EBCM) | 040 |
Electronic Suspension Control Module (ESC) | 056 |
Dash Integration Module (DIM) | 064 |
Instrument Panel Module (IPM) | 065 |
Rear Integration Module (RIM) | 066 |
Inflatable Restraint Sensing and Diagnostic Module (SDM) | 088 |
Instrument Panel Cluster (IPC) | 096 |
Radio | 128 |
Audio Amplifier | 129 |
Remote Playback Device - CD Changer | 130 |
Digital Radio Reciever | 137 |
Cellular Telephone Module | 144 |
Vehicle Communication Interface Module (VCIM) | 151 |
Driver Door Modules (DDM) | 160 |
Front Passenger Door Module (FPDM) | 161 |
Left Rear Door Module (LRDM) | 162 |
Right Rear Door Module (RRDM) | 163 |
Memory Seat Module (MSM) | 166 |
Steering Column Module | 168 |
Driver Door Switch Assembly (DDSA) | 170 |
Remote Control Door Lock Receiver (RCDLR) | 176 |
Theft Deterrent Control Module | 192 |
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 node alive message has not been received from a module with a learned identification number within the last 5 seconds.
Conditions for Clearing the DTC
| • | A current DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction. |
Diagnostic Aids
When multiple Loss of Communication DTCs are set concurrently, the cause is likely to be 2 opens in the ring portion of 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
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Data Link Connector Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems | |||||||||||||||||||||||
1 | Did you record any of the following DTCs?
| Go to Diagnostic Trouble Code (DTC) List in Doors | Go to Step 2 | ||||||||||||||||||||
2 |
Important: Use the control module ID number list in order to determine which modules are not communicating. Test the following circuits of the module that is not communicating for an open, short to ground or high resistance:
Refer to the following:
Did you find and correct the condition? | Go to Step 7 | Go to Step 3 | ||||||||||||||||||||
3 |
Refer to the following:
Did you find and correct the condition? | Go to Step 7 | Go to Step 4 | ||||||||||||||||||||
4 | Test the class 2 serial data circuits of the module that is not communicating for an open or high resistance. Refer to the following:
Did you find and correct the condition? | Go to Step 7 | Go to Step 5 | ||||||||||||||||||||
5 | Inspect the harness connector of the module that is not communicating for poor connections and terminal tension at the following circuits:
Refer to the following:
Did you find and correct the condition? | Go to Step 7 | Go to Step 6 | ||||||||||||||||||||
6 |
Important: Perform the set up procedure for module if required. Replace the module that is not communicating. Refer to Control Module References for the applicable replacement procedure. Did you complete the replacement? | Go to Step 7 | -- | ||||||||||||||||||||
Does the scan tool display any DTCs which do not begin with a "U"? | Go to Control Module References for the applicable Diagnostic System Check | Go to Step 8 | |||||||||||||||||||||
8 | Select the Display DTCs function for the modules which had the Loss of Communications DTC set. Does the scan tool display any DTCs which do not begin with a "U"? | Go to Control Module References for the applicable Diagnostic System Check | Go to Step 9 | ||||||||||||||||||||
9 |
Did you complete the action? | Go to Control Module References for the applicable Diagnostic System Check | -- | ||||||||||||||||||||
