Service 4WD light
 

Hi all. I'm new here after just buying a good used high millage 2000 S10 LS 4WD. It needs some TLC and a bunch of small fixes. One of which is the Service 4WD light does not light up on the instrument cluster during self test (turning key on). Swapped out with another cluster with same result.The 4WD itself does seem to work fine when changing between 2W Hi, 4W Hi and 4W Low. I'm one of them who likes everything to work as designed plus it would just be nice to have that warning light if I do indeed have problems with the 4WD system. I'm just looking for direction as to where to troubleshoot or whatever. Does the cluster self test on it's own? Or is it done by the BCM? Or is the Service 4WD light activated by the TCCM? Is there a way for me to simulate a fault in my 4WD system that would activate my Service 4WD light? Any insight would be greatly appreciated. Thanks!

Check all related fuses.

If the 4WD works I wouldn't worry about it.

Yeah I checked all my fuses and visually they all look good. I did notice yesterday while testing the shifting from 2Hi to 4Hi that I had to press the 4Hi twice before the button lit up solid at around 25-30 mph. Then I shifted back to 2Hi (the 2Hi light came on solid) and immediately heard a faint grinding sound which continued until I came to a near stop when the noise suddenly stopped and I could feel what felt like the 4WD disengaged or the front lockouts disengage. I know I should be able to shift between 2Hi and 4Hi on the move but something doesn't seem right. Any ideas?

You could make sure that the vacuum lines that go to the 4WD actuator (and all vacuum lines) are not cracked/dry rotted and also inspect the vacuum actuator under the battery tray.

If that actuator is torn it won't actuate correctly. Also look to see that it isn't full of transmission fluid as that can happen to if the vacuum valve on the top of the transfer case fails.

Another thing that could fail is the switch assy in the dash. They are cheap to replace but I'd do that only after I determined that the vacuum actuator and the cable to the axle is good. It also might be something in the front axle.

being that he has a service 4 wheel light there will be no switch on top of the transfer case, this will be a system with the auto button and it uses a vacuum switch on the firewall. as recommended check all the lines and the firewall vacuum switch, you will want to make sure the switch vacuum lines are not backwards or the diff stays locked until the vacuum leaks down ....the grinding could be coming from the axle locking system inside the front diff but hopfully not.

Thank you guys for your input! I do physically have a Service 4WD light in the instrument cluster. It just doesn't come on during self test (ignition on) nor does it come at at any other time. And I do not have a 4WD Auto button. I do have the three button switch. I will check the vacuum lines, actuator and cables within the next few days. I have verified that both 4WD Hi and 4WD Lo do work but at that time I was at a stand still while changing from 2WD to 4WDHi/Lo and visa versa. I have only tried engaging and disengaging 4WD Hi once while on the move as I described earlier when I heard the noise. It wasn't a hard grinding noise but more faint to almost inaudible. As I slowed so did the noise then before I came to a complete stop (>5 mph) I could feel something release or disengage and the noise stopped. So I'm pretty sure that though my 2WD switch indicator was lit solid there was still something still engaged in the 4WD system until I came to near stop. I'll be checking the transfer case and differential oil levels as well. Thanks again!

Oh , My mistake....Your service 4x4 light will never light , that is a generic dash and the light is only for the 4 button system. I think the noise you heard was probably the axle lock ....maybe a bit worn or chewed up and won't quite mesh properly when moving..... If it were mine I would listen to the Doctor, if the 4x4 works i wouldn't worry about it but I would select 4x4 when stopped only to avoid more wear of the diff axle lock

There is nothing wrong with it. Nothing to check further. It's not broken. Use and enjoy.

Thank you so much! I've done a lot of research on the Service 4WD light including owner's manual but nothing ever came up suggesting it was for the 4WD Auto 4 button option only. Owners manual just states it should come on during self test (unless I missed something) else take it to authorized service center or whatever if lit. Very good to know and not have to worry about that. And as far as engaging/disengaging the 4WD I will just be ginger with it. Only really need it during the winter months when we we get nailed with snow although I might do some off road trail riding sometime perhaps. Thanks again! Cheers

I went over the 4 button switch and the TCC module with a soldering pencil and reflowed all the solder joints, replaced the dashpot under the battery and the truck's 4x4 traction control was like brand new again.