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Thread: "charging sys warning"

  1. #1
    jakenotfromstatefarm is offline Cadillac Owners Member
    Automobile(s): 2008 STS
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    "charging sys warning"

    I have an '08 STS that the charging system warning came on the other morning. Being somewhat mechanically inclined I kinda thought it was an alternator issue due to it saying it was not charging. Replaced the alternator and I have the same issue. Charged the battery to full charge........same issue. Replaced battery with new battery.........same issue. I have exhausted my level of being a barn yard mechanic. Is there something else I can do or is this now a dealer issue. Appreciate all advice thank you!


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  3. #2
    CMNTMXR57's Avatar
    CMNTMXR57 is offline Cadillac Owners Connoisseur
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    Re: "charging sys warning"

    Dealer issue. Sounds like a GMLAN serial data communications issue. Not to add injury to insult, but you spent a lot of money for no reason.

  4. #3
    jakenotfromstatefarm is offline Cadillac Owners Member
    Automobile(s): 2008 STS
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    Re: "charging sys warning"

    Quote Originally Posted by CMNTMXR57 View Post
    Dealer issue. Sounds like a GMLAN serial data communications issue. Not to add injury to insult, but you spent a lot of money for no reason.
    Thank you appreciate your help. I can't get one over the counter can I?

  5. #4
    CMNTMXR57's Avatar
    CMNTMXR57 is offline Cadillac Owners Connoisseur
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    Re: "charging sys warning"

    Get what?

    The network in your car is CAN (Controlled Area Network), so essentially the PCM runs the car, like a network at your office, subletting processes and commands to other slaves, in this case modules. In order to communicate with one another, their is constant serial data sent back and forth between all those units to authenticate and verify statuses. This is the GMLAN (GM Local Area Network).

    What sounds like it is happening, is that there is some disruption in that LAN communication between those units that control the information on the charging system and it's state (our car is constantly monitoring SOC, or State Of Charge), and communicating it back to the central PCM. Any disruption in that signal and/or communication is what is generating this issue.

    You need to take it into someone with a CAN capable scan tool and that can troubleshoot it. A Caddy dealer with a Tech2 and CANdi module or the new MDI interface setup will be able to do this.

  6. #5
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    Re: "charging sys warning"

    Quote Originally Posted by jakenotfromstatefarm View Post
    I have an '08 STS that the charging system warning came on the other morning. Being somewhat mechanically inclined I kinda thought it was an alternator issue due to it saying it was not charging. Replaced the alternator and I have the same issue. Charged the battery to full charge........same issue. Replaced battery with new battery.........same issue. I have exhausted my level of being a barn yard mechanic. Is there something else I can do or is this now a dealer issue. Appreciate all advice thank you!
    Hey Jakenotfromstatefarm,

    I am sorry to hear that you are having difficulties with your ’08 STS. If you would like me to look into the issue or set up a visit with a dealer, please PM me your VIN, pertinent information, and any dealer you would prefer to work with. Have a great day!

    Austin J.
    Cadillac Customer Service

  7. #6
    jakenotfromstatefarm is offline Cadillac Owners Member
    Automobile(s): 2008 STS
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    Re: "charging sys warning"

    Thanks made the appointment with the dealer and taking it in there this week. Appreciate your advice! After I submitted the last post I thought that was pretty stupid question but didn't know if there was something over the counter I could get to fix the problem. Thanks again.

  8. #7
    CMNTMXR57's Avatar
    CMNTMXR57 is offline Cadillac Owners Connoisseur
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    Re: "charging sys warning"

    Not a stupid question. These things have monitors, monitoring monitors...

    For example, this past weekend, my Wife's Chrysler van through a P0480... CANbus could not communicate with the fan relay. Simple stuff like that is monitoring itself.

  9. #8
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    Re: "charging sys warning"

    Quote Originally Posted by jakenotfromstatefarm View Post
    Thanks made the appointment with the dealer and taking it in there this week. Appreciate your advice! After I submitted the last post I thought that was pretty stupid question but didn't know if there was something over the counter I could get to fix the problem. Thanks again.
    Hey jakenotfromstatefarm,

    Glad to hear you made an appointment with the dealer. Please let us know how everything turns out. If you do end up needing assistance, feel free to shoot us a PM.

    Austin J.
    Cadillac Customer Care

  10. #9
    TimmyC is offline Cadillac Owners Connoisseur
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    Re: "charging sys warning"

    A communication error will set a U**** code. I think it might be the current sensor on the negative battery cable.

    Let us know when you get it back from the dealer.

  11. #10
    CMNTMXR57's Avatar
    CMNTMXR57 is offline Cadillac Owners Connoisseur
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    Re: "charging sys warning"

    Not always.

    Ran across many on CAN and non-CAN GM cars over the years that would have class II data issues. Some would set a U code, some won't. Each vehicle has clightly different parameters, but in some, it depends on a cycle count of how many times it's tried to establish that connection, I.E. "pinging" the modules, that after so many attempts, then yes, it will set.

  12. #11
    jakenotfromstatefarm is offline Cadillac Owners Member
    Automobile(s): 2008 STS
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    Re: "charging sys warning"

    Well the issue is the positive cable running from the battery to the jumper to the alternator to the starter.........with a 200 amp fusible link in it. Dealer wants $700 dollars to change it. $350 for the part and another $350 for labor.........found OEM on Ebay for $150. Going to attempt tochange myself which I am certain I can do it by the looks of things. Will let you know how it goes! Thanks for the advice!

  13. #12
    Ludacrisvp's Avatar
    Ludacrisvp is offline Cadillac Owners Connoisseur
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    Re: "charging sys warning"

    IIRC that will require a lot of work and force you to replace a gasket of some kind due to the cable routing.
    I looked into it at one point... I don't think you can get to the wire connected to the starter without pulling the top of the motor off...

  14. #13
    TimmyC is offline Cadillac Owners Connoisseur
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    Re: "charging sys warning"

    Getting to the starter is the easy part. You have to remove the supercharger. Not that bad.

    Getting the cable out of the harness is a bitch. It is routed along the cylinder head and the held on with bolts that might be too long to remove with the engine in the car. You might have to drop the engine cradle down to get to them.

    You could always just leave the bad cable in there and run the new one over it. A little hack but might be the only way.


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