U1192
DTC U1001-U1254
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC U1016
- Lost Communication With ECM/PCM
DTC U1017
- Lost Communication With Engine Control Module
DTC U1024
- Lost Communication With Transmission Control Module
DTC U1026
- Lost Communication With ATC/TCCM
DTC U1040
- Lost Communication With Electronic Brake Control Module
DTC U1041
- Lost Communication With Electronic Brake Control Module
DTC U1064
- Lost Communication With Body Control Module (BCM)
DTC U1088
- Lost Communication With Sensing and Diagnostic Module (SDM)
DTC U1096
- Loss of IPC Communications
DTC U1097
- Loss of DIC Communications
DTC U1098
- Loss of HUD Communications
DTC U1099
- Loss of HUD Communications
DTC U1111
- Lost Communication With Chime Module
DTC U1128
- Loss of IRC Communications
DTC U1129
- Loss of AMP Communications
DTC U1133
- Lost Communication With DVD Player
DTC U1137
- Lost Communication With Digital Radio Receiver
DTC U1144
- Loss of PHN Communications
DTC U1147
- Lost Communication With Onstar
DTC U1151
- Lost Communication With Onstar
DTC U1152
- Lost Communications With HVAC Control System
DTC U1153
- Lost Communication With Climate Control Panel
DTC U1160
- Loss of DDM Communications
DTC U1161
- Loss of PDM Serial Data
DTC U1162
- Lost Communications With Convenience Control System
DTC U1166
- Loss of MSM Communications
DTC U1167
- Lost Communications With Rear Seat Audio/Rear HVAC
DTC U1173
- Lost Communications With Moveable Roof Module
DTC U1176
- Loss of RFA Communications
DTC U1192
- Lost Communication With Vehicle Theft Deterrent
Diagnostic Fault Information
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 (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 for that modules "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.
A module with an internal class 2 serial data circuit malfunction or which loses power during the current ignition cycle would have a Lost Communication DTC set by other modules. The modules that can communicate will set a DTC indicating the module that cannot communicate. 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.
Conditions for Running the DTC
* Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.
* Diagnostic trouble codes U1300, U1301 and U1305 do not have a current status.
* The vehicle power mode, ignition switch position, 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.
Action Taken When the DTC Sets
The module(s) is never signaled, therefore the specific subsystem(s) will not function.
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 of 50, without a repeat of the malfunction.
Diagnostic Aids
* Use the DTC Descriptor list above to determine the module which is not communicating.
* Some modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no module output voltage circuit is shorted to ground before replacing the module.
* This diagnostic can be used for any module that should communicate with Class 2 serial data providing the vehicle is equipped with the option that uses that module.
Reference Information
Schematic Reference
Data Communication Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Data Link Communications Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for Scan Tool Information
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector of the module that is not communicating.
2. Ignition ON, verify that a test lamp illuminates between all battery positive voltage circuits and ground.
• If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module.
3. Verify that a test lamp illuminates between all ignition voltage circuits and ground.
• If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module.
4. Test for less than 1 ohm of resistance between the module ground circuits and ground.
• If greater than 1 ohm, repair the ground circuit for an open.
5. Test for less than 1 ohm of resistance in the Class 2 serial data circuit between the non-communicating module and the module that displays the DTC.
• If greater than 1 ohm of resistance, test the Class 2 serial data circuit for open/high resistance.
6. If all circuits test normal, replace the module that is not communicating.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Control Module References (Programming and Relearning) for module replacement, setup, and programming