Envoy, Rainer, Trailblazer 2006-2007

5.3L V8 VIN M Auto 12

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Trouble Code: U1088



Lost Communication With Sensing and Diagnostic Module (SDM)

Possible Causes:



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.
 

Trouble Code: U1096



Loss of IPC Communications

Possible Causes:



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.
 

Trouble Code: U1097



Loss of DIC Communications

Possible Causes:



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.
 

Trouble Code: U1098



Loss of HUD Communications

Possible Causes:



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.
 

Trouble Code: U1099



Loss of HUD Communications

Possible Causes:



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.
 

Trouble Code: U1111



Lost Communication With Chime Module

Possible Causes:



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.
 

Trouble Code: U1128



Loss of IRC Communications

Possible Causes:



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.
 

Trouble Code: U1129



Loss of AMP Communications

Possible Causes:



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.
 

Trouble Code: U1133



Lost Communication With DVD Player

Possible Causes:



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.
 

Trouble Code: U1137



Lost Communication With Digital Radio Receiver

Possible Causes:



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.
 

Trouble Code: U1144



Loss of PHN Communications

Possible Causes:



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.
 

Trouble Code: U1147



Lost Communication With Onstar

Possible Causes:



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.
 

Trouble Code: U1151



Lost Communication With Onstar

Possible Causes:



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.
 

Trouble Code: U1152



Lost Communications With HVAC Control System

Possible Causes:



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.
 

Trouble Code: U1153



Lost Communication With Climate Control Panel

Possible Causes:



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.
 

Trouble Code: U1160



Loss of DDM Communications

Possible Causes:



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.
 

Trouble Code: U1161



Loss of PDM Serial Data

Possible Causes:



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.
 

Trouble Code: U1162



Lost Communications With Convenience Control System

Possible Causes:



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.
 

Trouble Code: U1166



Loss of MSM Communications

Possible Causes:



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.
 

Trouble Code: U1167



Lost Communications With Rear Seat Audio/Rear HVAC

Possible Causes:



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.
 

Trouble Code: U1173



Lost Communications With Moveable Roof Module

Possible Causes:



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.
 

Trouble Code: U1176



Loss of RFA Communications

Possible Causes:



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.
 

Trouble Code: U1192



Lost Communication With Vehicle Theft Deterrent

Possible Causes:



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.
 

Trouble Code: U1241



Lost Communication With Scan Tool

Possible Causes:



DTC U1241 does not indicate a system malfunction and will not cause any warning indicators to illuminate. When DTC U1241 sets, cycle the ignition and use the scan tool to clear the code, no further diagnosis is necessary.
 

Trouble Code: U1241



Lost Communication With Scan Tool

Trouble Code: U1254



Lost Communication with XXX

Possible Causes:



An intermittent open between a module and a star connector may cause this DTC to set.
 
A poor connection at a module or a star connector may cause this DTC to set.
 
An intermittent open in a star connector may cause this DTC to set.
 
An open voltage or ground circuit to a module may cause this DTC to set.
 
An internal module malfunction may cause this DTC to set.
 

Trouble Code: U1254



Lost Communication with XXX

Possible Causes:



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.
 

Trouble Code: U1255



Loss of Class 2 Communication

Possible Causes:



If a malfunction such as an open fuse to a module occurs while serial data communication is active, a Lost Communication DTC for the specific module is set as a current DTC in other modules. When all serial data communication becomes inactive, the current Lost Communication DTC is cleared, but the history DTC remains. When serial data communication resumes, the module with the open fuse will not be learned by the other modules, so DTC U1000 or U1255 is set as current by the other modules. In the event of a malfunction occurrence while serial data communication is inactive, DTC U1000 or U1255 is set without a loss of communication DTC for the specific module.
 

Trouble Code: U1300



Class 2 Data Link Low

Possible Causes:



These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to Scan Tool Does Not Communicate with Class 2 Device .
 
An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to Scan Tool Does Not Communicate with Class 2 Device .
 

Trouble Code: U1300



Class 2 Data Link Low

Possible Causes:



This DTC can be retrieved with a current status from the engine control module (ECM) only, because the ECM is the gateway between the class 2 and high speed GMLAN serial data circuits, and the ECM diagnostics is performed on high speed GMLAN link. Refer to Data Link Communications Description and Operation for more information about data link communication.
 

Trouble Code: U1300



Class 2 Data Link Low

Trouble Code: U1301



Class 2 Data Link High

Possible Causes:



These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to Scan Tool Does Not Communicate with Class 2 Device .
 
An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to Scan Tool Does Not Communicate with Class 2 Device .
 

Trouble Code: U1301



Class 2 Data Link High

Possible Causes:



This DTC can be retrieved with a current status from the engine control module (ECM) only, because the ECM is the gateway between the class 2 and high speed GMLAN serial data circuits, and the ECM diagnostics is performed on high speed GMLAN link. Refer to Data Link Communications Description and Operation for more information about data link communication.
 

Trouble Code: U1301



Class 2 Data Link High

Trouble Code: U1305



Class 2 Data Link Improper Signal

Possible Causes:



These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to Scan Tool Does Not Communicate with Class 2 Device .
 
An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to Scan Tool Does Not Communicate with Class 2 Device .
 

Trouble Code: U1305



Class 2 Data Link Low or High

Possible Causes:



This DTC can be retrieved with a current status from the engine control module (ECM) only, because the ECM is the gateway between the class 2 and high speed GMLAN serial data circuits, and the ECM diagnostics is performed on high speed GMLAN link. Refer to Data Link Communications Description and Operation for more information about data link communication.
 

Trouble Code: U1305



Class 2 Data Link High or Low

Trouble Code: U1500



VCIM Internal Malfunction

Possible Causes:



The diagnostic procedure used for DTC U1500 in OnStar® systems with single module generations of OnStar® differ greatly from previous generations with 2 modules. While these older generations denoted a failure of the 3-wire bus between the modules by setting a U1500, single module OnStar® systems use this DTC to denote an internal module failure. The determination of whether a one or 2-module generation of OnStar® is used should be confirmed. Refer to OnStar Description and Operation .
 
This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the VCIM.
 
If this DTC is retrieved as both a current and history DTC, replace the VCIM.
 

Trouble Code: U2100



High Speed CAN Communication Bus

Possible Causes:



This DTC cannot be retrieved with a current status. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with high speed GMLAN Device. Refer to Scan Tool Does Not Communicate with High Speed GMLAN Device .
 
An intermittent condition is likely to be caused by a short on the high speed high speed GMLAN serial data circuits. Use the Scan Tool Does Not Communicate with high speed GMLAN Device procedure in order to isolate an intermittent condition. Refer to Scan Tool Does Not Communicate with High Speed GMLAN Device .
 

Trouble Code: U2100



Controller Area Network (CAN) Bus Communication

Possible Causes:



These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom Scan Tool Does Not Communicate with High Speed GMLAN Device .
 
An intermittent condition is likely to be caused by a short on the class 2 serial data circuit.
 

 
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