4wd Not Engaging..fuse Problem?

kokesh · November 24, 2008

(2000 GMC Jimmy SLT)

Hi,

I took out my stereo a few weeks ago to add an iPod adapter and in the process I briefly had the battery disconnected. I'm not sure that this problem is a result of that but at any rate my 4wd does not engage. When I hit the 4hi switch or auto 4wd switch the light blinks repeatedly (forever) until I hit the 2hi switch again. There is no evidence that the front axle is making any attempt at engaging (no sounds or gripping)

I read in other topics and http://www.alldatadiy.com/techtips/GMC/20021230b.html here that one way to try to fix this was to recycle the modulator essentially by taking out and then replacing the fuse for 4wd or transfer case. In that techtips page they said the fuse would be labeled TCASE. In my fuse block there is only one fuse that looks like it is associated with the 4wd system. It is called 4WD. It is number 15 in the fuse block and is 10A. The description in the manual for this fuse is "4WD Switch, Engine Controls (VCM, PCM, Transmission)

I thought I would take out this fuse per the instructions on the techtips page. However upon taking off the fuse block cover I saw that there was no fuse in place in the 15th slot. I'm not sure if there is supposed to be but one would imagine that there isn't a 4WD fuse for no reason.

I thought about simply putting a 10A fuse in this slot and seeing what happens but I don't know if that could potentially harm the system.

If it's not a fuse problem, I'm guessing it's a switch problem judging from what I've read on these boards. When I took out the dash to do the iPod install, I did not unplug the 4WD harness but, on the other hand, it may have gotten knocked around a little. Not very much though; I kind of doubt (without knowing much about the switches) that it is a switch problem since I didn't even unplug it. And the lights flash.. But I don't know.

I would first like to know a) if there should be a fuse in the 15 slot where it says 4WD, b) if there is any other fuse that the 4WD is linked to..I don't see anything in the manual about a transfer case fuse, so I'm assuming that the 15 fuse is the tcase fuse. (by the way, there are no other fuse slots that are vacant, except for slots 1, a, and b, which are meant to be not used)

Thanks a lot!

alwcurlz · November 24, 2008

(2000 GMC Jimmy SLT)
Hi,

I took out my stereo a few weeks ago to add an iPod adapter and in the process I briefly had the battery disconnected. I'm not sure that this problem is a result of that but at any rate my 4wd does not engage. When I hit the 4hi switch or auto 4wd switch the light blinks repeatedly (forever) until I hit the 2hi switch again. There is no evidence that the front axle is making any attempt at engaging (no sounds or gripping)

I read in other topics and http://www.alldatadiy.com/techtips/GMC/20021230b.html here that one way to try to fix this was to recycle the modulator essentially by taking out and then replacing the fuse for 4wd or transfer case. In that techtips page they said the fuse would be labeled TCASE. In my fuse block there is only one fuse that looks like it is associated with the 4wd system. It is called 4WD. It is number 15 in the fuse block and is 10A. The description in the manual for this fuse is "4WD Switch, Engine Controls (VCM, PCM, Transmission)

I thought I would take out this fuse per the instructions on the techtips page. However upon taking off the fuse block cover I saw that there was no fuse in place in the 15th slot. I'm not sure if there is supposed to be but one would imagine that there isn't a 4WD fuse for no reason.

I thought about simply putting a 10A fuse in this slot and seeing what happens but I don't know if that could potentially harm the system.

If it's not a fuse problem, I'm guessing it's a switch problem judging from what I've read on these boards. When I took out the dash to do the iPod install, I did not unplug the 4WD harness but, on the other hand, it may have gotten knocked around a little. Not very much though; I kind of doubt (without knowing much about the switches) that it is a switch problem since I didn't even unplug it. And the lights flash.. But I don't know.

I would first like to know a) if there should be a fuse in the 15 slot where it says 4WD, b) if there is any other fuse that the 4WD is linked to..I don't see anything in the manual about a transfer case fuse, so I'm assuming that the 15 fuse is the tcase fuse. (by the way, there are no other fuse slots that are vacant, except for slots 1, a, and b, which are meant to be not used)

Thanks a lot!

I would check in the engine compartment for more fuses. There is a box there with more fuses that may have what you're looking for. The fuse box cover should have an illustration where it is too.

Good luck!

kokesh · November 25, 2008

Ah, good call. I had looked at the diagram in the manual but apparently not closely enough since I see it this time ..in this case it is called ATC for automatic transfer case.

Is it worth trying to "reset" the transfer case module by pulling out this ATC fuse in the engine fuse block and then waiting a few minutes and putting it back in? No harm can come from trying this, right?

alwcurlz · November 25, 2008

Ah, good call. I had looked at the diagram in the manual but apparently not closely enough since I see it this time ..in this case it is called ATC for automatic transfer case.

Is it worth trying to "reset" the transfer case module by pulling out this ATC fuse in the engine fuse block and then waiting a few minutes and putting it back in? No harm can come from trying this, right?

I would see no problem with that! I would be tempted myself to actually disconnect the battery as well and let it set for a while, maybe 30 min so the computer could soft-reset.

Good luck!

Mike G · November 26, 2008

Try the reset, then I have a couple others for you.. On my 96 there was a vacuum modulator that went out, this was located under the battery tray and easy to replace, so look for something comparable (grab a service manual or check the library). After that, you need to look to the 4wd encoder motor, they have a short life span for some reason.

--Mike