2006 HHR LT; 2.4L; automatic; 158,000 mi

Erratic Gauge and Warning Light Readings

Problem Description: Vehicle intermittently displays erratic gauge readings, warning lights, and DIC messages. When this condition is occurring the power steering may fail and transmission will shift erratically (hard shifts and gear skips). The condition occurs for several minutes then usually goes away by itself leaving the security and traction control warning lights illuminated until multiple cycles of the ignition switch have been performed to clear the warning lights. During some instances of this problem, the problem occurred while driving and did not cease until the vehicle was stopped and the ECU was disconnected and reconnected. The vehicle can go for days, weeks, or months without recurrence. Visits to two different dealerships have resulted in recording and clearing the DTCS codes with both dealerships unable to replicate / troubleshoot the problem.

DTCS Codes Found and Cleared
P0300 Engine Misfire Detected
P0575 Cruise Control Switch Signal Circuit
U0073 Controller Area Network (CAN) Bus Communication
B3935 Transponder Authentication Error
U2100 CAN-BUS Communication Malfunction
U2103 Fewer Controllers On Bus Than Programmed
U2107 Lost Communications with Body Control System
C0561 System Disabled Information Stored
C0550 Electronic Control Unit (ECU) Performance

My belief is that there is an intermittent CAN failure (U codes) with either a software anomaly, poor or interrupted communication signals, or an individual component failure. I believe the other codes are either symptoms of the CAN bus failure or unrelated. I have researched multiples forums and I do see what I believe to be other incidents of this problem.

Does anyone know of the history of this issue and potential causes / solutions?

 

Is it equipped with OnStar?

 

No ... unfortunately the vehicle is not OnStar.

 

Ok, that rules out the VCIM connector which will cause the U codes. I would be checking the ECM harness for chaffed wires by any metal brackets.

 

Another area to check is the fuse box under the hood. If tapping on the side or top of it recreates the problem, then it could be the electrical center or the wire plug ins underneath.

 

ChevyMgr ... Thanks for the responses; I have inspected the harnesses previously and yet again last night. The conduit does not display any evidence of chaffing through; I do agree that it seems that a potential cause of this issue could be wire integrity ... especially since there is a relationship to the getting the problem to stop by disengaging the connectors ... thus disturbing the positioning of the harnesses. If problem persists I may consider removing the conduit to inspect the wiring directly. I have not removed the electrical center for further inspection ... but I will consider that option upon the next occurrence.

Last occurrence was three days ago; dealership cleared codes; so far no recurrence with about 400 miles of driving. But it's only a matter of time ... (frustrating).

 

It's happened again at about 1,200 mi of driving since the dealership cleared the codes. This time the problem occurred for about 30 seconds while driving at 75mph; then the problem disappeared by itself while still driving leaving the security and traction control (T/C) indicator lamps illuminated. While pulling off the interstate the vehicle remained in high gear until I stopped the car. I then cycled the ignition four times to clear the indicator lamps and the transmission shifting issues.

Since this occurrence another 300 miles of driving without incident. Haven't taken the car back to the dealer for another $95 session of code recording and clearing. Frustrating.

 

I'd suspect the fuse box too. Be a good idea to look at the bottom of it. It could be a plug in connection somewhere also.

 

You could ask your dealer to install their VDR (Vehicle Data Recorder). This will capture what is happening when it occurs.

 

FWIW: How is the condition of your battery ?