klhpraise

I have what I have been told is a Chevrolet 2008 Malibu with a 3.5L V6 engine installed. For the last several months I have been having a very annoying intermittent electrical problem. When I first noticed it the only two systems which seemed to be affected were the Traction Control (indicator would indicate system was shut off when I didn't shut it off and the LED readout on dash would state Traction Needs Serviced) and the Theft Deterrent Indicator would illuminate on the dash. As it progressed the Cruise Control and the Air Conditioner would stop working for about a day at a time. I took it in for service about 1 1/2 months ago and they said they found loss of communication codes (which they then cleared), but found no trouble codes; They test drove vehicle after clearing codes and no new codes appeared so they told me they couldn't help me until the intermittent becomes more regular and they can actually find trouble codes. Now that the vehicle just went out of warranty (about 7 days ago) the problem has shown it ugly little head again and has also now affected the gas gauge and the speedometer in addition to the other systems previously mentioned. Has anyone any clue what could be causing this intermittent behavior? Is there a commonality between these systems (common ground, common connector to the BCM or the ECM, common supply wiring, common cable in wiring harness). Could it be the BCM is defective? Now that the warranty is up the dealer all of the sudden has a change of heart and believes it may be what they call the computer (not sure if they are referring to the BCM or the ECM). Where is BCM in this vehicle? Any help would be greatly appreciated!

Thanks in advance,
Karl

JimWD

Here is an opinion.
"U" codes are sure enough codes. And if you have seen DIC messages, there will be "B" or "C" or "P" codes stored in History. Current codes will trigger the DIC messages, but if the DIC message does not appear at the next KEY-ON event, a History code will remain for some number of start cycles depending on the code.

The remainder of your post pushes me to suspect battery terminal or cable corrosion and/or various corroded chassis ground connections.

OR, faulty diagnosis.

OR, poor communication from the person describing the situation to you.

klhpraise

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What is meant by U code?

Unfortunately, what I posted is almost word for word what my service adviser told me. I couldn't understand why he wasn't concerned with several different lack of communications codes being stored in the system! I would think that lack of communication between control modules would be something that service personnel would really want to try to locate the cause of.

I asked him about commonality between the systems affected and could there be a loose connector or something, since they had already been in my dash 4 times trying to locate and fix a bad buzzing noise. They also had been in my console to replace a broken shifter cable. So I concluded that maybe there was a bad or loose connector or bad ground or something of that sort. He gave me a lecture on the sophisticated nature of the electrical systems in these vehicles, that the only way they serviced these vehicles was to look at stored computer codes and assured me that they could do nothing for me until the problem came back and manifested itself more fully with additional codes.

Have you heard anything about a GM bulletin in regards to Terminal Fretting Corrosion (especially on BCM) and how to correct it?

Thanks,
Karl

JimWD

A U code is a network code. And network codes come and go like clouds. It's a safe bet that 99% of the OBDII cars on the road would display one or more U codes at any given time.

The service adviser was giving it to you straight. U codes are not specific enough to point directly at the problem (if there really is a problem rather than a clock pulse hiccup). They were looking for a stored C code in the case of your traction control issue and did not find it.

If you are inclined and tooled up to DIY, start with my battery terminal & cable suggestion. There will be many chassis ground locations on the vehicle any one of which could be affected by temperature, humidity, or phase of the moon.

You will have to wait for a specific B, C, or P code to be set before you can narrow a problem down to a specific part, module, or connector.

klhpraise

JimWD,

Thanks for your clear and concise reply about the U code. I had an appointment to
have the Malibu looked at again this morning and I took it in with several marked up wiring diagrams in hand. I explained to the service adviser what I saw in common in those wiring diagrams and where they might look to find the annoying intermittent. They had the car for about 6 hours this time and actually really started searching for the problem. The service adviser said that they found the problem and have repaired it. He said they found several wires behind the engine block (where they left engine compartment to enter firewall) that had some worn insulation on them and they occasionally touched causing loss of communication between the control modules. They called GM and arranged for the repair to be made under the warranty which just expired 8 days ago.

Thanks for you help in this matter,
Karl

JimWD

Sounds like a happy ending IF that wire bundle was the cause of your issues and you now have a permanent repair.

The fact that the labor costs were approved under warranty is a goodwill gesture and speaks volumes about the "new" GM.

The question I would be pondering is; why did the insulation wear off?

Glad to provide an assist. But you had the wiring diagrams and the words for the service advisor.

Thank you for the feedback. Happy motoring.

Chevrolet Customer Service

Karl,

I am glad to see that this concern has been resolved. If you have any further questions or concerns, please feel free to contact me. Thank you.

Tricia, GM Customer Service.

klhpraise

Tricia and JimWD

Unfortunately, the problem I described earlier (8/16/2011) has not been resolved. The fix dealer made didn't solve the issue. The problems have been mounting (especially in the last 3 days) and I took the vehicle in with all of the problems happening at once (yesterday) and they still couldn't find any active codes to diagnose the actual problem. In fact I have had added symptoms in the last few days. In addition to those described previously I have also had the Odometer flash "ERROR' occasionally and it took 3 tries yesterday to get my starter to turn over and start the car. Also I have noticed the car being harder to drive, message appearing on DIC about Power Steering and it occasionally makes a hard noise when shifting out of Park into Reverse. My GM dealer can't seem to help me and tell me that because they could locate any trouble codes (couldn't verify a problem exist) back a month before my Body to Body warranty expired that any work could not be covered under warranty. They told me that they talked with GM and that I should have at least 5 trouble codes showing up for all the issues I have been having. Yet the only codes that have shown up thus far are U2100 (CAN Controller Off), U2107 (PCM lost Comm with BCM) and a new one today of B0561 (ABS $43 - System Disabled Information Stored Invalid Serial Data Received.). They said that GM thought that with all these problems that the most likely culprit was a faulty BCM (cost and labor around $365.00), but they were only 60% sure that would correct the problem. I have looked at battery cables (no corrosion) an the ground s that I can locate easily in the engine area all appear to look good and are tightened securely. This is getting to be more than a little frustrating for all parties concerned; I have had vehicle in for checking on 3 separate occasions and they can't help me. The thing they repaired the last time was charred electrical wiring near the Purge Solenoid.

kevinkpk

If your paying the dealer, MAKE THEM GET IT RIGHT! Don't settle for anything less. They are a dealer that represents the OEM, Chevrolet.

klhpraise

I goofed in my earlier message today. The third code was actually C0561 (ABS $43 - System Disabled Information Stored Invalid Serial Data Received.) not B0561. I won't pay dealer anything (won't let them change out BCM) until they can locate the real problem. We can't be replacing one module after another hoping to solve the problem. It appears to me that all the errors stored in History thus far are all related to the High Speed CAN bus (communications failure on the bus). Unfortunately, the way this bus is connected between the various control modules is in a serial fashion (From ECM to TCM to ECBM to Power Steering Control Module to BCM). A short or an opening in the wiring or circuit at any of these modules could be causing a loss of communications, so the ECM shuts down the whole circuit to be on the safe side (U2100 - CAN Controller OFF). I would think that the dealer's technician could use his/her knowledge of this interconnection scheme, a Volt-Ohmmeter and basic troubleshooting skills to locate the short or open. I guess until the vehicle just totally stops working on me that they will not take the effort because of the intermittent behavior and No Codes being found other than those previously discussed. I don't have good enough knowledge of the location of the various Modules involved, where to find each connector in the wiring diagrams and what the proper Ohms and Volts measurements Observed should be. If I did I would locate the offending connector or module myself.