Diff-lock light randomly coming on

The dif-lock light on my dash keeps coming on by itself. It's not as bright as when it's locked, and the dif doesn't lock by itself, the light just comes on. If I lock the dif the light gets brighter, then when I unlock it the light goes off, but it comes back on in a few minutes.

 

I have a 2nd Gen 5-lug, but I had a similar problem with the Auto-LSD light (which is only supposed to come on when the limited-slip rear diff is engaged via pushbutton, and by default the traction control automatically gets turned off); When the truck was still under the bumper-to-bumper warranty (which would have been prior to September 30th, 2012), the Auto-LSD randomly came on and wouldn't shut off. I immediately freaked out because the owner's manual explicitly says not to use the Auto-LSD on dry pavement, and I believe I got it to go out, but it came back on again not long after, and I brought it to the dealer since I was due for an oil change. The dealer checked it out free of charge, found nothing amiss, and in the eight years since that happened I don't think it's happened again...

 

Another circuit is grounding back through the locker bulb.

Could be a loose ground could be a metal dirt bridge .

Any other cluster lights not working??

Is it effected by the lights being on??

Maybe when you hit a bump??

 

I experimented with it today, and I'm pretty sure it isn't tied to the headlights. All other cluster lights are working fine. If I lock it in the light gets brighter. When I unlock it the light goes out, but starts coming on again within seconds. Very dim at first and gradually getting brighter. After about a minute it is almost as bright as when it's locked in. It never gets quite as bright as when it's locked. It doesn't appear to be tied to bumps because it will come back on even if I am not moving, even if the engine isn't running. One interesting thing is yesterday I locked the dif and when I unlocked it the light went out and didn't come back on. Today when I started out is never came on. At one point I decided to test it and locked the dif. Light blinked and then came on bright as normal. Then when I unlocked it it went out, but gradually coming back on again. I tried locking and unlocking it a half dozen times but couldn't get it to stay off.

I think maybe what ever part in the dif lock that moves when you lock it, isn't moving back all the way. Yesterday it did move all the way back that one time, but all other times it's not. But then again I could be wrong. It locks and unlocks just fine, and it doesn't appear to ever try to lock unless I push the button.

 

That’s because the light grounds through the Diff Lock Detection switch on the rear Diff.
When the Diff is Locked, it grounds the bulb.
If you want to narrow down the problem, unplug harness at the Diff.
The light should not come on.
If it does, the problem is not the limit switch or Locker motor.

The Ground wire should be Blue/Yellow.

I will warn you to be careful unplugging the harness.
They can be brittle and break after many years.

 

I unplugged it and the light went out. Plugged it back in the the light stayed off. Locked the dif, light blinked and came on as it should. Unlocked and it went out, and so far has stayed out. Maybe there was just some corrosion on the connection that I knocked loose unplugging it.

 

I had the exact same symptoms on my truck as you. Ultimately, I took the Diff Lock limit switch out and checked with a meter, it was engaging with 100+ ohms of resistance depending how I played with the plunger, so bad limit switch. Since I had everything apart on the diff, I put the reverse light switch from my transmission (manual, 3.4L V6, 1999 truck) in the diff, which cured my problem. I still need to get a new reverse light switch for the transmission LOL. Note that if you are trying to order a new switch, the reverse light switch comes up significantly cheaper on www.toyotapartsdeal.com, etc. than the locker switch. They are exactly the same (at least on my truck). Should be about $45 for a new one if I recall.

 

Thanks mike I’ll be trying to diagnose it, I have the same issues plug just got the Yukon rebuild kit for the e locker too and it was all fine till about 2 months.