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Thread: 2006 C6 Auto - electrical issue - can't find cause

  1. #1

    Default 2006 C6 Auto - electrical issue - can't find cause

    While I was driving, all the gauges went to zero except the MPH. The AC stopped, although the blower kept working. The radio died and so did Onstar. I turned the car off, and it started fine and then acted up again a few minutes later. By the time I got home, the car died - nothing was responding to the FOB. I towed the car to the dealer. Here is what they did:

    -replaced the door remote receiver - did not fix the problem, and they left that part in the car.
    -they replaced the BMC - they told me it was fixed. It started without issue several times (maybe more than a dozen) and they could not get the car to act up again. Before i picked up the car, they deiced to take out the door receiver and replace it with the original unit - the car acted up again. So, they put the new unit back in and thought it was fixed
    -I went to pick up the car, and before I pulled out - it started doing the same thing. After another week, they finally gave up, and stated that they could not get the car to act up again. They left the parts in, and refunded the cost (I couldn't believe they did that, although they probably trashed the old units). BTW, there were no codes when they scanned it.

    I took the car to another mechanic, who could not get the car to act up - so I took it home, drove it for a week without issue, then, while driving i decided to get on it a little - i used the sport mode and paddle shifters - rev'd it up while driving, and the same thing happened. I got home, the car started fine - drove fine that day. The next day, the same thing - radio went dead, ac KEPT working this time, gauges went to zero except MPH. This time I noticed that the only thing that reset was the average MPG - I found that odd. When I parked, I turned the car off, and attempted a restart - nothing. A few minutes later, I tried again, and it started just fine. I drove it all over, without issue. When I put the scanner on it, I got a yellow light, but no faults displayed.

    I am puzzled - I don't know what to check.... HELP!!!

  2. #2

    Default

    HI there,

    Well, honestly, you have a communications failure.

    And there will be codes in systems, because as modules look for communications, it sets codes if they do not see communications with those modules.

    Now that being said, I believe you have a loss of ground source to a control module, resulting in the module dropping the entire communications line.

    You really will need to have someone scan the vehicle with a GM TECH 2 to determine what is going on.

    Has the vehicle had any powertrain components out of it? Engine? Transmission? Any accident damage???

    Allthebest, Paul
    GM World Class Certified Service Technician.
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  3. #3

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    Quote Originally Posted by c4c5specialist View Post
    HI there,

    Well, honestly, you have a communications failure.

    And there will be codes in systems, because as modules look for communications, it sets codes if they do not see communications with those modules.

    Now that being said, I believe you have a loss of ground source to a control module, resulting in the module dropping the entire communications line.

    You really will need to have someone scan the vehicle with a GM TECH 2 to determine what is going on.

    Has the vehicle had any powertrain components out of it? Engine? Transmission? Any accident damage???

    Allthebest, Paul
    When I had the car at the dealer, I asked if they used a tech2 tool and was told, yes. The Tech2 tool would be a common tool at a dealer, right? The car is clean, no damage and no mod's .... all original with only 30K miles.

    I used my Innova 3100e tool, and contacted the company regarding what I found; they said that the tool is showing that a drive cycle needs to be performed - I am getting a solid yellow light and a flashing EV icon, but no DTC's. I just looked up how to complete a dive cycle and will try that soon.

    When you state "loss of ground source to a control module, resulting in the module dropping the entire communications line." does that mean that the module is bad or that the line 'feeding' the module is grounded somewhere, or both?? If you think it could be a bad module, I take it modules are those square 'fuses' located in the fuse box???

    Thanks for you assistance, much appreciated.

    Sami K

  4. #4

    Default

    one more thing - i just had the car smog checked, and it passed just fine. Doesn't the car have to complete a 'drive cycle' before it would pass smog??

    Thanks,
    Sami K

  5. #5
    Join Date
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    What Paul is referring to is one of the many, many ground points that are in car most likely has become disconnected or not making good connection to ground. Which ever module may have lost that ground could be causing problems with the whole cars communication.

    My guess would be a bad connection since you seem to indicate it is not happening all the time so the cars vibration during driving would make the ground intermittent , but just a guess on my part.

  6. #6

    Default

    HI there,

    Your INNOVA WILL NEVER EVER scan all the control modules within the vehicle. I know this because I OWN ONE.

    You will get ABS, ECM, TCM and thats about it.

    Your still missing RCDLR, BCM, LDCM, RDCM and others critical to function of your vehicle.

    Obviously, someone is not being truthful with their diagnosis of this condition.

    In my 10 years serving C6, EVERY SINGLE communications failure of this magnetude, leaves codes.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  7. #7

    Default

    Quote Originally Posted by c4c5specialist View Post
    HI there,

    Your INNOVA WILL NEVER EVER scan all the control modules within the vehicle. I know this because I OWN ONE.

    You will get ABS, ECM, TCM and thats about it.

    Your still missing RCDLR, BCM, LDCM, RDCM and others critical to function of your vehicle.

    Obviously, someone is not being truthful with their diagnosis of this condition.

    In my 10 years serving C6, EVERY SINGLE communications failure of this magnetude, leaves codes.

    Allthebest, Paul
    Thanks for your advice. I am going to take the car to another tech soon. I checked the 'blue' connections mentioned earlier, and they seemed fine, but I am no expert. So far, the car is running perfect BUT .... when I connect the Innova DTC reader, i don't get an all green, instead I am getting a yellow light with no codes, very odd. Anyhow, I will update when I get it checked with Tech2 tool.

    Doesn't it seem odd that the only electrical component that reset was the average MPG?? Oh well. . . .

    Thanks,

    Sami Khal

  8. #8

    Default

    Quote Originally Posted by Samik View Post
    Thanks for your advice. I am going to take the car to another tech soon. I checked the 'blue' connections mentioned earlier, and they seemed fine, but I am no expert. So far, the car is running perfect BUT .... when I connect the Innova DTC reader, i don't get an all green, instead I am getting a yellow light with no codes, very odd. Anyhow, I will update when I get it checked with Tech2 tool.

    Doesn't it seem odd that the only electrical component that reset was the average MPG?? Oh well. . . .

    Thanks,

    Sami Khal
    I have not had time to get to a Tech2 tool yet, but something happened that might be the answer. While driving the car, I set the CID to display the voltage, several times while at a stop, in drive with the AC and Radio on, I noticed the voltage steadily drop to 12.1 volts, and then hover there until I rev'd up the motor in while in neutral. While driving, the voltage ran around 13.4, Could this indicate an issue with the alternator? And, could that cause the issues described above???

  9. #9

    Default

    HI there,

    This would tell me to check your battery cable terminals at the battery FIRST before anything else, but,,,,,,,,,the alternator will output electricity based on ECM command from the BCM voltage sense, NOT on its own.

    Once again, this comes back to the data. This is where many technicians miss details.

    It is the DATA that will tell you if there is issues.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  10. #10

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    Quote Originally Posted by c4c5specialist View Post
    HI there,

    This would tell me to check your battery cable terminals at the battery FIRST before anything else, but,,,,,,,,,the alternator will output electricity based on ECM command from the BCM voltage sense, NOT on its own.

    Once again, this comes back to the data. This is where many technicians miss details.

    It is the DATA that will tell you if there is issues.

    Allthebest, Paul
    Here is the latest update .... the car started acting up and now it sits in the garage, and I can't get it to start. The battery has 12.5v, there is power to the engine and interior lights lights, but no brake lights. FOB does NOT unlock the car. I have disconnected the batter (negative terminal only) and disconnected / reconnected the 'blue' connectors under the drivers footwell, reconnected the battery and still nothing. I can not get the car into 'ACC' mode to connect a code reader.

    Is there anything you can think of that I can try (without wiping out the programming) to 'reset' the electrical system???? Good Lord, this is extremely aggravating....

  11. #11
    Join Date
    Jul 2008
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    Ontario, Calif.
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    You can't erase the programming of the systems without using special software so you don't have to worry about that. To reset the ECU completely disconnect both terminals from the battery and touch them together for 10 seconds. That should reset the ECU. Reconnect the terminals and see if it will start etc.
    2015 Stingray Z51 w/ Magnetic Ride Control & 8-speed Automatic


  12. #12

    Default

    HI there,

    Well, you will not have brake lights when the ignition is off, so that's ok.

    a strong word of warning, DO NOT KEEP CONNECTING AND DISCONNECTING THE BCM. This will prematurely wear out the terminal tension if you rock the connectors back and forth.

    As for the rest, I would say you may have a BCM failure, but once again, a Tech 2 would be needed for accurate diagnosis.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  13. #13

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    ok, here is the latest. The (new) dealer has it, and states that the only Tech2 message they are getting is something like "loss of communication", and thats it. The nightmare continues . . . . .

  14. #14

    Default

    Hi there,

    OK, so then, what is their diagnosis???

    You have 2 different communications lines to test.

    What codes did they have?

    I doubt very much that both lines are dead.

    You wouldnt be able to have any function anywhere, not even start car.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  15. #15

    Default Update 6-11-15

    Quote Originally Posted by c4c5specialist View Post
    Hi there,

    OK, so then, what is their diagnosis???

    You have 2 different communications lines to test.

    What codes did they have?

    I doubt very much that both lines are dead.

    You wouldnt be able to have any function anywhere, not even start car.

    Allthebest, Paul
    The only error that was shown was the failure to communicate. I was asked if the car was recently serviced for the headlight recall, to which the answer was yes. The vehicle was in inoperable, they couldn't get it to do anything. The tech took apart the fuse box and put everything back together, and the car started right up and is running perfectly. However Time will tell, it seems I could not go more than a week without an issue with the gauges and electrical acting up. The Tech thinks that the previous headlight recall work was not done properly.

    I will post an update in a week or so or sooner if something happens again.
    Last edited by Samik; 06-11-2015 at 10:19 AM.

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