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Chevrolet Tahoe Suburban 4 Wheel Drive Indicator Lights



  • niktnikt Posts: 24
    To bryons,

    I realize your Tahoe is a 2001 and mine is a 1999, but where did you find the ATC fuse? I looked at my manual and opened the fusebox on the left front fenderwell, but didn't see the ATC fuse. The fusebox I opened has many fuses and relays in it. Is this the correct panel or is there another fusebox you're talking about, or does the ATC fuse have a different name or designation??

    Thanks, NIKT
  • niktnikt Posts: 24
    A big thanks to all who made suggestions. My 1999 Tahoe now has a correctly functioning 4WD system. If you recall, NIKT (that’s me) said that the unit was stuck in 2HI and would not engage any other mode. There were various suggestions, but here’s what worked for me:

    1.- Find ATC fuse. This took longer than everything else because I kept looking for an “ATC” fuse. At least on my ’99 Tahoe, there’s no fuse so marked. My manual did list a fuse in the small fuse panel on the left side of the instrument panel, but not in the panel over the left front wheel. It’s a 20Amp fuse in the No. 2 position, and is identified as “Transfer Case.” It was blown.

    2. – I pulled the T-case fuse (#2) and the Accessory Light fuse (#3) and left the car sit for about 5 minutes with the ignition switch off.

    3 – I replaced the 20 Amp fuse with a 25 Amp fuse, because some people suggested that cold weather can result in a higher current draw in the 2WD-4WD shift motor. I put back the 10 Amp Accessory Light fuse which was OK.

    4. – As some suggested, I then switched the ignition On and Off 5 times to clear any trouble codes stored in the Trans Control Module.

    5. – I fired up the engine and watched as the red “Neutral” light on the control button panel blinked off. My Tahoe had been stuck in 2HI, but then the 4HI button lit showing that mode was now engaged. I pushed the 2HI button and the transfer case shifted OK. Out on the street I engaged all the Transfer Case modes and everything seemed to work OK.

    Again, a big thanks to you all, and I hope what I did works for you too.

  • kiawahkiawah Posts: 3,666
    I'd put a 20Amp fuse back in. If you really do have some sort of problem (which will trip now the 25Amp fuse), you may burn some wiring (or a wiring block or connector) which would be very costly to repair.

    You can also keep another spare if it does blow later. If it does, you'll know exactly what are where to replace it.
  • mmalkmmalk Posts: 2
    checked the 20amp atc fuse that was to easy.subscibe to all data not all you want to know,. to seek more diagnostics.The selector seems to have power and replaced the modual.Has anybody gone further and replaced the tccm thier on ebay 165.00 pluged a scaner in ,no codes?
  • niktnikt Posts: 24
    To kiawah,

    Thanks for your thoughts. You make good sense and I will change the fuse back to a 20 Amp unit this morning and keep some spares handy, Also, I will operate the 4WD drive selection every other day or so to keep the shafts or other components moving freely.

    Also, is there another recommended lube oil for the transfer case? Some forums talk about a "blue" fluid for better lubricity, or is that to improve the Auto 4WD?

    You know, I have never used the Automatic 4WD feature. I bought my Tahoe used (50,000 miles) about 9 years ago. I tried using the Auto 4WD in the snow, but I didn't like what I thought was a harsh engagement and avoided ever using it. When accelerating on snow or wet pavement, I engage 4HI to get up to speed and then engage 2HI. In winter here in suburban Chicago, when we get blowing and drifting snow, I engage 4HI and it seems to get me through just fine. I then shift back to 2HI when I'm back on dry ground. I'm coming up on 140,000 miles and I like my Tahoe just fine. The only repairs of consequence (how do you spell Co$t?) have been replacement of one fuel injector and about 2 years later, the in-tank fuel pump.

  • I have a 98 suburban 1500 4x4 LT 5.7 L with 165,000 miles

    I'm having some 4 x4 problems.

    The push buttons will engage 4 HI, but when it kicks in, the front wheels feel like they will pull to one side then the other and has an audible mechanical growl.

    I've never had a problem with the 4 wd system on this truck. I don't know where to start with diagnosis.

    The lights on the 4wd buttons all function, and the 4x4 system engages when each range is pushed , and dis-engages when 2 hi is pushed. It just pulls and growls when engaged.

    The symptom seems to be worse when using the auto 4 wd feature.

    Where should I start?

    I've had this rig since new.
  • niktnikt Posts: 24
    To Markseiler,

    I can't speak with the authority of a mechanic, but only from my perspective as a Tahoe owner. You may already know this, but don't engage 4WD on dry ground.
    If I correctly understand the way the 4WD system functions, engaging the front axle also causes the front axle to become a locked axle. That's necessary to prevent all the drive torque going to one wheel on very slippery ground, leaving you with very little or no traction. This means (to me) that one should avoid sharp turns of the front wheels while in 4WD unless you are on very slippery (snowy, icy) ground. I recall once forgetting to disengage 4WD and I could feel a terrific binding when I made sharp turns on dry ground.

    Did you read my previous entry? I bought my Tahoe used, and didn't like the way Auto 4WD engaged and never used again. Maybe a Tahoe technician could advise on lube oil specs for the transfer case. I hope this helps.

  • I have the same problem on a 2003 Chev Blazer, with nearly identical symptoms.

    If you believe the push button 4WD selector, all is fine. It switches in and out of 2 or 4WD no problem. However, based on recent driving I don't think it's actually engaged. If I actually get some decent slippage (ie, icy accelerating), it will grind from the front end like crazy. Sounds similar to grinding gears on a manual transmission (it's an auto, for reference). Only happens on slippage in 4WD.

    Took it into the dealer, they've replaced a seal which they say went bad and let oil into my vacuum lines which then took out a servo and actuator. Still grinds, so they're thinking it's actually taken chunks off the gear and sleeve for the 4WD. $800 so far into it, gonna be about $800 more for the gear and sleeve. :cry: Does this sound right for symptoms/diagnosis? I'm not much of a mechanic and REALLY get lost on tranny/transfer case type stuff.
  • niktnikt Posts: 24
    Sorry, I can't help on this one. I have to defer to a real mechanic on this problem.

  • I took it to a shop, they said bad transfer case, they can put in a new one for $2,000

    i found a use one at the junk yard for $300. my friend and I are going to put it in and see what we get. They are supposed to be heavy so a little bit tricky to do in the driveway. I'll let you know how it turns out.
  • niktnikt Posts: 24
    After replacing the Transfer Case fuse (See my message #25), my 4WD worked OK for a while, but yesterday the fuse blew again and I now believe I have to replace the shifter motor. The local Chev dealer parts manager says the required motor is GM P/N 12386247 for $497.00! I did some digging and found a Dorman (new, not rebuilt) shift motor, Dorman P/N 600-902 that is supposed to be an exact replacement, and which costs $136.99 at RockAuto.

    Am I on the right track here? If not, any other suggestions?

    Has anyone out there made this repair? Is Dorman a reliable product?

  • Hi Nikt,
    Looks like I have a similar problem with my wife's 1997 Tahoe as you are having. She shifted to 4WD the other day and now the thing is stuck in 4wd. Thanks to you I went right to the proper fuse and checked it - it was good. But I have a couple of questions about your entry #25, if you'd be so kind as to answer them. First; Why did you remove the Accessory Light fuse (#3) as well? Was that part of the reset procedure? Second has to do with switching the ignition On and Off 5 times to clear the codes. Can you tell me where you got that information. I'm asking becasue I couldn't find it on the web, but I may not have structured the search properly? Anyway either it's truly stuck in 4wd or I did something wrong because Nothing I did helped. :surprise:
  • niktnikt Posts: 24
    Hi grenneam,

    I pulled the the ATC and Accessory Light fuses because it was suggested by a Chev/GM mechanic in another forum. To understand what these fuses protected, and before doing any of the things I described, I tried to find schematics for the transmission control system at our local library without success, so I can't tell you what effect pulling the fuse had. That same mechanic suggested turning the ignition on and off 5 times.

    I thought I saved the the web address of that forum, but I couldn't find it in the my "Favorites" list. If I find it, I will let you know. I do recall it was an"Ask the Expert" style forum, and answers were free if were willing to wait a day or two for an answer. However, by paying a small premium you could get a quick return with an answer.

    Do you have any thoughts about, or know of anyone who used a Dorman shifter motor?


  • For Nikt,
    Thanks for your reply. I forgot to pull the #3 fuse - I'll try it again with that out. I'm just getting into this stuff with this vehicle and am looking at replacing the TC motor as well. I really don't know anything about the Dorman Motor - just that it appears more expensive than the Cardone that I'm looking at.
    I feel like I've entered Automotive repair hell. I've got 2 vehicles that won't pass inspection, The Tahoe and my wife's 2001 Sienna. We made an attempt with the Tahoe and found out that not only was it not simple (cheap) to fix the 4WD problem but the MIL indicator was burnt out and it also needs a Cat converter and possibly something else. The Sienna is an even bigger nigthmare in that it too has Cat ConV problems and a bad KnockSensor. The Knock Sensor is about $180 and is located underneath the intake manifold so it'll be at least that much to replace it. The Fun part is that the Cat Conv for the Sienna looks like an Unobtainable part until at least Feb 2010 and cost somewhere between 350 and 1400 dollars depending on where I shop. It's also tucked away in such a manner to prohibit anyone with a blow torch from working their magic. The only saving element is that my State has a kickout clause on inspections that allows a Waiver if you spend > $150 on a vehicle trying to fix it. So that's a temporary solution. This has all happened over the last couple of days, I feel a little shell shocked and am just trying to orient my self with what is going on and who/what to try and fix first.. LOL :sick:
  • OH yeah - I forgot this. In my web searches I found mention that replacing the TC motor might necessitate re-programming the TCM (Transmission Control Module)!! Have you seen anything like that? If you have, do you have any idea as to how that's done, or whether it a big deal or not ? :confuse:
  • I have a 2003 Chevy Suburban 1/2ton. I had it in 4 wheel drive, snowy, slushy, wet and rainy. Driving about 50 the front end made a bunch of clanking noise and grinding. There was nowhere to pull off. I switched it into 2 wheel and was able to pull into a parking lot about 2.5 miles. I put it in park, then back into drive, it clanked once really loudly and then made no more noises until I tied to put it back into 4 wheel drive. Can you help?
  • niktnikt Posts: 24
    Thanks to all of you for your comments. I am just regular Tahoe owner, not a crackerjack mechanic, so I can't answer the questions you folks have. What little I know I learned from reading the Chilton and other shop manuals at our local public library and
    surfing the net to find other Chevy and Tahoe forums.

    I hope there is a guy with experience in these matters to advise us on repair and/or needed reprogramming procedures. I am digging into this as best I can because our local Chevy dealer wants $800 to $900 to replace the shift motor which is out of the question for guy not working a steady job (me). I just want to be sure I'm doing all the right things before I buy a shifter motor and try to install it.

    So once again, if any of you folks out there have replaced the shifter motor (sometimes called the encoder motor ( its GM part number is 12386247) please tell us all about and any problems you encountered.


  • niktnikt Posts: 24
    A note of caution for all to consider-----I mistakenly thought my Tahoe needed an encoder (2WD-4WD shifter) motor, of GM p/n 12386247 or Dorman 600-902. I did more checking (I should have done it first) and looked at the RPO codes on the ID sticker on the glove box door. Turns out that the transfer case RPO is not NP1, but actually NP8. The correct encoder (shift) motor is GM p/n 12474401 that is serviced by Dorman 600-901. The plugs and wiring are different and the units are not interchangeable.

    I'm sure a lot of you already know this stuff, but I confess to being a beginner. Years ago, when I scrounged for boneyard parts, RPOs and such weren't a factor--you just found what fit the car you were fixing. Of course my new questions are: Has anyone had experience installing this shifter motor? Any trick stuff to know about? Does any reprogramming have to be done? Is there a cheaper source for this motor?

    Many thanks to you all and Merry Christmas,

  • Ok I have been watching this thread and here is my problem. After recent snow I put the truck in 4 hi now it won't come out into 2wd. the dash switch clicks 2wd blinks then it goes back to 4hi. If you push 4 auto it will change into it but not 2wd. check 4x4 is on but I scanned it and it shows no codes. I pulled the fuses 2 and 3 waited 30 minutes reinstalled but that didn't do it. before i start throwing parts at it where do I start the switch ? My thinking is the transfer case motor 1st or switch 2nd because when the switch clicks i hear no noise at the transfer case. Any Ideas ?
  • I have a very similar problem with my 97 Tahoe and I've got it in the Shop right now. The guy is supposed to replace a Part on Monday. I'll Let you know how it turns out. The vehicle is stuck in 4 whl Hi and won't go to either 2 whl Hi or 4 Whl LO. I don't have an auto button that I know of. It my wife's truck for pulling a horse trailer so I don't get involved with it much. :blush:
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