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  1. #1

    Default Battery Draining

    Hello all,

    I have a 1999 Silverado 1500 LS 4x4 (New Body Style). A new problem has presented itself over the last few of months. When the truck sits for a day or two at a time, the battery is drained. I didn't worry about it too much in the summer because 9 out of 10 days I would ride the motorcycle. Now that it is below freezing, it's becoming a problem.

    I've done some preliminary testing...
    - Put the truck on a Battery Tender and took the long way to and from work a couple days to make sure the batter had a full charge
    - Took the battery to AutoZone and had it tested. It is only 2 years old and it tested as strong.
    - Pulled out my multi-meter and put it in series with the positive terminal on the battery. I expected a slight load (maybe .10 or less for radio memory and a radar detector), but it is pulling between 2.5 and 8 amps.
    - Narrowed it down to a single fuse under the hood. The fuse is labeled TBC.

    I called the two GM factory service departments in town and they were no help. First one said I would have to make an appointment and the second told me it had something to do with traction control.

    I pulled the fuse and the truck will no unlock with remotes or start. Also, with the fuse out, the security light stays on the display. I'm going to assume it has something to do with either the remotes or the security features of the truck.

    Does anyone have any additional information on this and what the possible root cause is? I'd like to get it solved before it really gets cold since it turns over slowly after one cold night. I've been driving it daily but it is still sluggish to start in the mornings.

    Thanks in advance.

  2. #2

    Default

    I guess I should add that the alternator is putting out 14.2 volts so it is fine.

  3. #3
    Jr. Mechanic
    Join Date
    Dec 2009
    Location
    Deep River Ontario
    Posts
    100

    Default

    TBC - Truck Body Control or commonly known as Body Control Module.

    sounds like there is a short to ground in that circuit, if you can find a pin out and check your connections for frayed or damaged wires that would be a good place to start.

  4. #4

    Default

    Quote Originally Posted by Viper View Post
    TBC - Truck Body Control or commonly known as Body Control Module.

    sounds like there is a short to ground in that circuit, if you can find a pin out and check your connections for frayed or damaged wires that would be a good place to start.
    Thanks for the info. I'll do a little digging from here. I did a little research on the Body Control Module and found that they exhibit these symptoms when they are going bad too. I hope that isn't the case.

  5. #5

    Default

    Update. Picked up a Body Control Module today for $50. I'm going to try to swap it out tonight. I'll post my findings. I'm still going to search for damaged wiring first so I'll post my ultimate fix.

  6. #6
    Jr. Apprentice
    Join Date
    Dec 2009
    Location
    Somerset, KY
    Posts
    20

    Default

    Yea, post what u find, I would be interested in knowing what it turns out to be.

  7. #7
    Legend

    Join Date
    Feb 2008
    Location
    Red Wing, Minnesota, United States
    Posts
    3,389

    Default

    So did you pull the battery when it wouldnt start or when it would start. If you pulled it when it would start it wouldnt show that the battery is bad or drained. So pulling and testing it when it wont start will be more accurate. If you are saying it tested good when the truck wouldnt start then I would inspect all the cables, corrosion at the starter end of the battery cable will draw alot of power on startup and give you false indications that the battery is bad. I went through a battery and a couple tow one year at college until I found this.
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
    285/75/16
    ___________________________
    Jason

  8. #8

    Default BCM Change needs a TECH2?

    When I had the same sort of issue I monitored the battery drain while the car(2000 Imp) was turned off. It seemed the car was "waking up" and the draw on the battery jumped from 40 mAmps to 500 -600 mamps. and the battery would die overnight. I was pulling the fuse for the BCM nightly so I would have power to crank it over the next morning. did this for a week, the dealer had to replace the BCM as it is spec'd to the VIN, so I guess they needed a tech2 to do it. I'm interested to see if you replace it on your truck without having to take it to the dealer for programing.

  9. #9

    Default

    Quote Originally Posted by jake's silverado View Post
    When I had the same sort of issue I monitored the battery drain while the car(2000 Imp) was turned off. It seemed the car was "waking up" and the draw on the battery jumped from 40 mAmps to 500 -600 mamps. and the battery would die overnight. I was pulling the fuse for the BCM nightly so I would have power to crank it over the next morning. did this for a week, the dealer had to replace the BCM as it is spec'd to the VIN, so I guess they needed a tech2 to do it. I'm interested to see if you replace it on your truck without having to take it to the dealer for programing.
    I just tried the swap (same part number) and it will not start with the new BCM. I had read somewhere that they sometimes need to be flashed. I'll call my mechanic friend and see if he can do it. I tried calling the local Chevy dealer buy apparently they are too busy to give me a price. They keep transferring me to different people who are not in this week.

  10. #10
    Sr. Apprentice
    Join Date
    Aug 2008
    Location
    Loganville, GA
    Posts
    57

    Default

    Quote Originally Posted by cmurphy84 View Post
    I just tried the swap (same part number) and it will not start with the new BCM. I had read somewhere that they sometimes need to be flashed. I'll call my mechanic friend and see if he can do it. I tried calling the local Chevy dealer buy apparently they are too busy to give me a price. They keep transferring me to different people who are not in this week.

    The BCM has to learn the Immobilizer code from the ignition switch. I don't know about chevy but at Saturn we didn't have to use the Tech2 for this procedure.

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