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, the module records and identification number of the transmitting module for the purpose State of Health monitoring Node Alive messages. 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 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 3 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 Integration 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 |
Digital Radio Receiver | 137 |
Cellular Telephone Module | 144 |
Vehicle Communication Interface Module (VCIM) | 151 |
HVAC Control Module Auxiliary | 154 |
Driver Door Module (DDM) | 160 |
Front Passenger Door Module (FPDM) | 161 |
Left Rear Door Module (LRDM) | 162 |
Right Rear Door Module (RRDM) | 163 |
Driver Door Switch Assembly (DDSA) | 164 |
Window Switch - Front Passenger | 165 |
Memory Set Module (MSM) | 166 |
Left Middle Door Module (LMDM) | 171 |
Right Middle Door Module (RMDM) | 172 |
Remote Control Door Lock Receiver (RCDLR) | 176 |
Steering Column Module | 168 |
Theft Deterrent Control Module | 192 |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC U1001 thorough U1254 Loss of ( XXX module) Communications
Conditions for Running the DTC
| • | The following DTCs do not have a current status: |
| - | B1327 |
| - | B1328 |
| - | 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 |
Important: Use the control module ID number list in order to determine which module is not communicating. Test the following circuits of the module that is not communicating for an open or a short to ground:
Refer to the following:
Did you find and correct the condition? | Go to Step 6 | Go to Step 2 | ||||||||||||||||||||
2 |
Refer to the following:
Did you find and correct the condition? | Go to Step 6 | Go to Step 3 | ||||||||||||||||||||
3 | Test the class 2 serial data circuits of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 4 | ||||||||||||||||||||
4 | Inspect the harness connectors 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 6 | Go to Step 5 | ||||||||||||||||||||
5 | Replace the module that is not communicating. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | -- | ||||||||||||||||||||
Does the scan tool display any DTCs which do not begin with a "U"? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 7 | |||||||||||||||||||||
7 | 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 Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 8 | ||||||||||||||||||||
8 |
Did you complete the action? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | -- | ||||||||||||||||||||
