Another 4wd question

[clr114]

Sorry for the long post, but I've searched and searched regarding the 4wd service light, but I think my problem may be different.:undecided

I changed out my alternator yesterday. Had battery disconnected, etc. While in there, changed my water pump, tstat,hoses, and spark plugs. I put the thing back together, went to crank, and nothing.:mad: Lights (dash) came on , but no crank. Pulled the sec system fuse, put back in, horn honked, locked truck with remote transmitter, unlocked, finally cranked. All was fine, except the SERVICE 4WD light came on about 3 seconds after the crank.
The indicator light is on the 2WD setting. I can turn the knob to A4WD or others, I can here the modulator sucking, but the indicator light stays on 2WD but flashes on A4WD, not steady. Wierd. I just tried it again after resetting computer, pulling #8, etc. I noticed that I can turn it to 4WD and it will blink on 4WD, but the 2WD light is steady. But if I put it in gear with all this happening, it seems to be engaging the 4WD like it should, just the SERVICE 4WD light is on and the indicator is "blinking". I'm not sure if it holds the 4WD long though. It's like it tries to go to the shift, but eventually goes back to 2WD.

Now, a month or so ago my original alternator went out. "yes, i'm on my second one now, finally bought a NEW one". I changed it. hooked everything up, truck ran, but the 4WD service light did the same thing. I don't remember how I fixed it, I think I tapped on the TC modulator with a mallet once or twice. Doesn't work this time.

Does the engine computer have to learn the Transfer case stuff also before it shuts that dang service 4WD light off? Seems to do this everytime the battery is disconnected for an extended time.

Any help would be greatly appreciated, I can sense the snow coming :) and I would LOVE to test the 4wd out this year.

[2002BlkLTZ]

I would bet the TCCM (transfer case control module) is the problem. I had the exact same symptoms, and it involved a $400 fix from the dealer. :cry:

[NotForBling]

Check ALL fuses relating to the 4X4 system...just in case...you never know. Could get lucky and it less than a $5 fix.

Although I have had my battery disconnected twice in the past few months and I didn't have that problem. Hope it's nothing big...good luck

[clr114]

Well, it did it again. Now it works fine:duh: . The light went out again and I can shift into different modes. Could the alternator being disconnected with the battery at the same time have something to do with it? I had a feeling in the back of my mind, (more like a faint glimmer of hope :weird: ) that it would work itself out. I'll probably get to the dealer sometime soon, because this can't be good. I think my truck has windows 98 or something...:drool

[MTPockets]

... I can turn the knob to A4WD or others, I can here the modulator sucking, but the indicator light stays on 2WD but flashes on A4WD, not steady. Wierd..

Dumb question on my part, but were you in gear and moving as you change from 2wd - A4wd - 4x4? You gotta be rolling for proper engagement. Sometimes everything splines up when you are sitting still, but it's rare.

Joel

[ylab]

That's odd about the rolling part, while I have switched mine in/out of A4WD and even 4WD while moving (fromt 2HI to A4WD does make a pretty good thud much above 35-40 btw), I've almost always shifted mine when stopped at a light or in the driveway before putting it in gear. - Never had an issue with it not engaging.

If you do get weird problems, I've had one a week ago when no light at all on startup after the truck sat a few days in extremely cold weather, pull the #8 fuse under the hood (ignition off) and then put it back in 5-10 seconds later.....it will reset the TCCM. (The #8 fuse is the farthest forward fuse along the edge of the fuse box facing the engine on I6 models anyway).

[clr114]

Actually I was driving and on a whim switched it to a4wd, it was blinking. Got back to the driveway and it was steady light and engaged. I left it there for a while, (beggars can't be choosers) now works fine. I checked the trak II fluid, was full. Just changed it a few weeks ago. I hope that was the only problem. Seems like everytime I take the battery loose for an extended time, it does this. Maybe the TCCM has to learn also. These computers sure are dumb once they wake up...:confused:

[regularjoe]

had the same problem i had to have the 4x4 switch replaced on the dash

[MichEnvoyBoy]

Ive had problems with my 4wd 2-3 times since Ive owned my truck (over 2 years now). My "service 4wd" would periodically illuminate on the dash. It only happened when I turned my wheel all the way left and/or parked on a hill (like pulling into a parking spot on a slight grade). It would go off after the next key cycle. It stopped after I replaced my front differential bearings.

The second time the lights on my 4wd selector went out. I had to pull the TCM fuse and 4WD fuses about 12 times to get it to "wake up" again. That was last spring. No problems since. But it did take alot of times and definately put up a fight. I think the TCM went out drinking the night before and had a hangover :D

The third time my truck switched into 4LO by itself :crazy: Almost scared the living crap outta me. The 4wd selector was still pointed at 2HI, but the light was on for 4LO. Never had so much binding drivetrain in my life! lol.
Anyways, I'd not give up hope before bringing it in. I "almost" brought it in last time my TCM went to sleep but my persistance prevailed and it woke up after pulling the fuse(s) a dozen times over 3 days.