Question about 2002 GMC Sierra

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Truck Battery Keeps Draining?

For the last 2 months i;ve been having problems with the battery in my truck, dies overnight, and if it sits for 8+ hours it will turn over really hard. i looked into it a bit and decided to poke around in my fuse box to try and find a draw coming from some where. i disconnected my battery and put one end of a test light on the post and the other on the cable and sure enough the light came on which leads me to believe that there is a draw coming from somewhere. i started pulling fuses and watching the light to see if it stays on or goes off. it stayed on for all of them except for my transfer case fuse the light went out. the "SERVICE 4WD" light is always on, but my 4wd always works when im in 4x4. i guess what im asking is that could a ATC fuse be draining my battery and would it be safe to drive without that fuse just always in 2wd

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Well the fuse itself is not the issue, but there could be a solenoid or other electrical component draining the battery. And also cause the light to be on.
I would have the body computer scanned for trouble codes to find out why the service light is on. There should be trouble codes just like when the check engine light is on.
You could probably pull the fuse and run it in 2wd also.

Posted on Jan 19, 2013


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Posted on Jan 02, 2017

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SOURCE: 1999 gmc jimmy stuck in

need to check the fluid in transfer case

Posted on Dec 20, 2008

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SOURCE: Check 4 wheel drive light appears after 4x4 is engaged.

transfer case make grinding in shake when in 4 wheel

Posted on Jan 24, 2009

  • 29 Answers

SOURCE: Service 4WD

service it like you would the truck engine it will have to be reset by the book almost like the truck i had that same problem

Posted on Oct 27, 2008

  • 1 Answer

SOURCE: 2004 GMC Sierra 1500 4wd. Auto transfer case light issue

I have the same problem. It is intermittent and sometimes shows up with service transmission message. To get rid of it just put the truck in park, press the 2 high button and shift into drive while it is still flashing. I will worry about it more when it blows up. You can drive with the vehicle showing the solid neutral and it seems to make no difference. It has to be a wake up problem between the control modules. It only happens on start up.

Posted on Sep 06, 2009

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SOURCE: Had 2001 GMC Sierra in 4WD Auto and went to put in

On the full size, the front actuator is electric, not vacuum.

When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.

Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.

I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.

GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.

Good luck. The actuator is usually the problem 90% of time but recheck all of the wire harness just to maker sure there is no short before replacing any parts.

Posted on Jan 07, 2010

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