Canyon, Colorado 2006-2007

2.8L L4 VIN 8 Std 5

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Trouble Code: U1254



Lost Communication with XXX

Possible Causes:

The following conditions may cause this DTC to set:



An intermittent open between a module and a star connector
 
A poor connection at a module or a star connector
 
An intermittent open in a star connector
 
An open voltage or ground circuit to a module
 
An internal module malfunction
 



1. Current DTCs before history DTCs unless told otherwise in the diagnostic tables.
 
2. The DTC which is reported the most times.
 
3. From the lowest number DTC to the highest number DTC.
 

Trouble Code: U1255



Class 2 Data Link

Possible Causes:



When a malfunction such as an open fuse to a module occurs while modules are communicating, a DTC U1001-1254 Loss of Communications is set. When the modules stop communicating,the current DTC U1001-1254 Loss of Communications is cleared but the history DTC remains. When the modules begin to communicate again, the module with the open fuse will not be learned by the other modules so DTC U1000 or U1255 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only DTC U1000 or U1255 is set.
 

Trouble Code: U1300



Class 2 Data Link Low

Possible Causes:



DTCs U1300, U1301, and U1305 cannot be retrieved while the condition is present. Diagnosis of these 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 or an open 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:



DTCs U1300, U1301, and U1305 cannot be retrieved while the condition is present. Diagnosis of these 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 or an open 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:



DTCs U1300, U1301, and U1305 cannot be retrieved while the condition is present. Diagnosis of these 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 or an open 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: 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.
 

 
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