RR Diff Lock Light turned on.

Ok Tacoma World, Iv'e been a reader for some time but never posted. I have some knowledge how stuff works on vehicles. so here is the strange issue.
2004 Tacoma Prerunner TRD but it does NOT have a locking rear Diff. Today I'm driving down freeway at 75mph and the RR Diff Lock light slowly turned on to full bright red. I slowed to 60mph and it slowly dimmed to off. I picked up speed again and it turned on again but stayed dim. So i took the next exit, stopped the truck, put it in park, turned off the truck. waited a moment then started and proceeded back down freeway at 75mph, light never came back on. Does anyone have an idea as to what may be occurring or what my truck is trying to tell me. Thank you for any input.

 

Interesting.

 

Mine does the same thing except i have a locker. There is a sensor on my rear axle beside the locker that is bad and the light comes on about 50% of the time. Doesnt bother me so ill replace it sometime. Are you sure you dont have a locker?

 

I am 100% sure i don't have a locker. From what i understand, there are 2 different axel sizes for the tacoma, the larger bell housing has the locker and the smaller one does not. i have the smaller axel, and my vin number also says i don't have the locker. and the space for the button on the dash for the switch has never been cut out.

 

Even still, just crawl under your truck and look for a locker or a sensor there that isn't tied to anything. Maybe it is getting a ground to the frame or the axle causing that light to come on.

 

Ill Check and post back, have to run some errands first.

 

I checked and there are no doo dads, gizmos, or whatchamacallits, just the normal fill and drain holes and brake lines. went and had the brakes checked just in case of an unknown sensor for them, but they are only 40%worn and no issues. Just had an idea, is there a vin number on the axel housing somewhere that i can use to verify the axel.?

 

No

 

Thanks for your input Ya all. next ill do a fluid change and see if it happens again. I'm tempted to pull off the drive line and bell housing cover and see whats inside. Cuz outside theres nothing.

 

Actually, the rear differential with the locker has an 8" rear end. The non locking (open) diff has an 8.4" rear end. So if you have the smaller rear end you may have gotten somewhere along the line a replacement axle that happens to be an e-locker axle.

 

My God i hope so, guess ill find out for sure when i get time to get it apart.

 

Howd you solve this one? Ive got same issue.

 

Is your truck an Off-Road?

Either way, I suspect a ground issue.
The light has power at all times, the diff lock detection switch (in the differential) grounds the light.
If your truck doesn’t have diff lock, you need to find out why it’s grounding out.

 

Something grounding back through the light .

Look at what shares that same ground point on the dash lights