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 |
Continuously Variable Road Sensing Suspension Module (CVRSS) | 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 |
Cellular Telephone Module | 144 |
Navigation Data Processor | 145 |
Vehicle Interface Unit (VIU) | 151 |
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 message from a learned identification number has not been detected for the past 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 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
The numbers below refer to the step numbers on the diagnostic table.
-
The following DTCs indicate a malfunction in the power door serial data circuit:
-
The following modules have a single wire connection to the class 2 serial data circuit. An open in the single wire will prevent communications.
-
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.
-
The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.
| • | U1161 |
| • | U1162 |
| • | U1163 |
| • | U1170 |
| • | Cellular Telephone Module w/UV8 |
| • | Driver Door Module (DDM) |
| • | Memory Seat Module (MSM) |
| • | Navigation Data Processor w/UY4 |
| • | Steering Column Module w/N37 |
| • | Vehicle Interface Unit (VIU) w/UE1 |
Step | Action | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Data Link Connector Schematics | |||||||||||||||
Did you record any of the following DTCs?
| Go to DTC U1161-U1163 or U1170 in Doors | Go to Step 2 | |||||||||||||
2 | Test the following circuits of the module that is not communicating for an open or a short to ground.
For the applicable Schematic, refer to Control Module References Control Module References in Body Control System. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 3 | ||||||||||||
3 |
Did you find and correct the condition? | Go to Step 10 | Go to Step 4 | ||||||||||||
4 | Inspect the harness connector for poor connections and terminal tension at the following circuits of the module that is not communicating:
Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 5 | ||||||||||||
Do the following modules communicate with the scan tool?
| Go to Step 7 | Go to Step 6 | |||||||||||||
6 | Test the class 2 serial data circuits of the module that is not communicating for an open. For the applicable Schematic, refer to Control Module References in Body Control Systems and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 7 | ||||||||||||
7 |
Important: Perform the module setup procedure if required. Replace the module that is not communicating. Refer to Control Module References in Body Control System. Did you complete the replacement? | Go to Step 10 | -- | ||||||||||||
Does the scan tool display any DTCs which do not begin with a "U"? | Go to Control Module References in Body Control Systems for the applicable Diagnostic System Check | Go to Step 9 | |||||||||||||
9 | Use the scan tool in order to clear the DTCs. Did you complete the action? | Go to Step 10 | -- | ||||||||||||
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 in Body Control Systems for the applicable Diagnostic System Check | Go to Step 11 | |||||||||||||
11 |
Did you complete the action? | System OK | -- | ||||||||||||
