U1133
DTC U1001-U1254
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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.
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 after completing the diagnostic procedure. Verification Tests