I have a 2000 blazer 4 door with the 4 button control and the service 4wd light likes to come on whenever I try to use my 4wd which sucks of course and sometimes if I just turned the vehicle off and on a few times it would go away other times I have had to unhook the battery and then it would work again but this time none of that’s working none of the lights are on for buttons on the selector idk to much about the system in this vehicle I have no previous experience with this kind of stuff but any help or ideas would be appreciated thanks in advance

 

If you are getting a warning light, then the issue is something that is electronically actuated.

A common culprit for these systems is a failed Transfer Case Control Module (TCCM). It lives under the passenger side kick-panel. When they are failing, you can hear the relays in it, behind the kick-panel, clicking several times. They should only click once for each change in transfer-case configuration. Some people have reported that a temporary fix can be accomplished by removing the kick panel and cleaning the electrical connector to the TCCM. If you go to replace the TCCM, be sure to get one for your 4-button system rather than the 3-button one.

Other failure points can be the 4wd selector switch (less common) and a solenoid in the transfer-case itself (not uncommon).

Another failure point is in the vacuum system that supplies the vacuum to engage the front axle using a vacuum actuator. That doesn't sound like it is your problem* but at this age, those vacuum hoses can begin to rot and leak. When this happens the HVAC system will often start acting wonky due to there being insufficient vacuum to operate the vacuum actuators used to direct the air in the HVAC system.

* I'm pretty sure a failure in the vacuums system will not give a warning light but it is so easy to check and fix, it should be looked at no matter what.

 

Okay I will have to look at and clean the tccm then and as far as vacuum I don’t think that is the issue as all the actuators for the climate system work and seem to have proper vacuum but that’s another thing I will double check and if cleaning doesn’t work I will look at getting a new 4 button control

 

Quick update I unplugged the tccm and got it out of 4 wheel drive but my local shop says they don’t have a way of testing the module so I’m thinking I will start with getting a new 4 button controller and if that doesn’t work I will see if I can get a new module and also wondering if driving with the module unplugged will cause any harm to the transfer cause for the meantime I don’t need 4wd as I’m not playing in any snowdrifts

 

Have you tried plugging the TCCM back in? Perhaps it will stay in 2wd.

Did you hear any clicking from it when you tried to change the drive setting? If so then I'd guess it is the TCCM that is bad.

 

No there was no clicking when I tried shifting does that mean it’s just the 4 button control if so that’s an easy fix

 

Unfortunately, no. Itjust could mean that tbe TCCM is totally shot. While the TCCMs are going out, they will often have the extra clicking.

 

Hmm okay I will hook it back up and try changing through the different modes and make sure it’s actually shifting and listen very carefully for any clicking
update I hooked it back up and nothing wouldn’t shift and the service 4wd light was still on does that mean I need a new tccm

 

These are very difficult to definitively diagnose without proper equipment. What you can do.......

Check 20A ATC fuse in underhood fuse center. If it is blown, then you can pretty much bet 95% that the 4WD encoder motor is bad. Either way check the big wires in the TCCM electrical connector for corrosion and repair if needed. Also know that sometimes excess current from a bad encoder motor will also take out the TCCM, especially when going through a corroded connector. Hardly ever is the control switches as they just trigger the TCCM to do it's thing.

Warning - both encoder motors and TCCMs are not cheap parts but may be cheaper than diagnosis at a dealership. If you get a TCCM make sure it is already programmed for your Blazer (like the Cardone ones).

NEVER EVER plug an encoder motor into the wiring without it first being mounted on the transfer case. Turn the transfer case stub with a wrench to find where neutral is before attempting to put a new one on.

Good luck

 

Hmm okay starting to think I might be getting into a bit more then I can bite off or more then I want to atleast I will be first to admit my limit of mechanics is pretty low