Dont worry, I did a search and couldnt find anything exactly like my problem...

I have an 03 Tacoma 4x4, and whenever I put it into 4 wheel drive, the stock locker automatically engages. However, the indicator light does not come on, nor does the ABS light. The "RR DIFF LOCK" button itself is not even engaged (not pressed in). The locker does not dis-engage when I play with the button, even while moving forwards, backwards, turining, engaging while moving, engaging while stopped...stays locked, no light. Why is this happening?

Please only reply if you know what the problem is, thanks!

 

Have you owned this truck for a while? Have you done any of the "gray wire" modifications or messed with the wiring harness?

The ECU won't give ground to the e-locker motor unless the vehicle speed is below 5 mph and the transfer case selector is in 4WD Low.

 

No mods; all stock. And the locker ALWAYS engages when in 4x4, even in 4H. Fortunately, it disengages once put back into 2H.
This sucks...

 

How do you know the locker is engaged??? The 2 systems are completely separate, so I can't see how this can even happen...

 

Here is a couple suggestions.

you need to eliminate things that aren't wrong.

Sounds like the switch in the transfer case that recognizes when the transfer case is in lo4 could be acting up, and is engaging as soon as the shifter is moved at all. Try crawling under there, and pulling off the locker harness. Clean the area up, and then, with the truck "on" but not running (just move the key to the on position, but don't start the truck) crawl under with a multimeter, and check the resistance on the switch. Then have someone shift the transfer case into 4wd hi, and check the resistance, then low.

The resistance should be infinite at 2wdhi, 4wdhi, and then should be none in 4wd low.

If that switch is okay, and functioning properly, hook the harness back up and move to the cab.

Remove the dash switch and drive the truck in 4hi, and 4 low a little bit. If the switch has nothing wrong with it, then the truck will still lock in 4hi, like it has been doing. If the swich is the culprit, it should stay unlocked.

As a last resort, if Toyota's parts are too expensive or you just get fed up with it, you can disconnect the factory locker harness completely, and purchase one for 40 bucks from Marlin Crawler. This will bypass the 4wdlo requirement completely, and so you'll be able to lock it when ever you choose.

 

The 4WLo switch on the transfer case has no ability to engage the locker, all it does is sends a signal to the lockers computer.

The way the system works is simple it gets 2 inputs that if not met won't allow the locker to engage. The first being an input from the speed sensor and the second from the 4 wheel drive low switch. You have to be below 5 mph and in 4WD low, either or both can be bypassed, by doing the "grey wire mod" to disable the 4 low switch and simply cutting the wire to the speed sensor at the locker ECU.

Now with that said to engage the locker requires the Locker button to be turned on. Once the button is depressed the locker light starts to flash and the ECU checks the 2 inputs, if the requirements are met a relay in the ECU is turned on running a motor, moving a shift fork to engage the locker, once engaged, a switch is turned on causing the flashing light to stay constant and a signal is sent to the ABS computer to disable the system.

I'll repeat this again, How do you know the locker is engaged????? The Locker ECU and the all the wiring is a complete separate system and there is no way the locker can turn on by simply putting it into 4WD.....

 

yeah, bruce makes a very good point. Are you sure the locker is engaged?

 

I am sure it is engaged, because when I turn sharply, the back wheels hop.
4WD does not disable the rear-differential's purpose...therefore, the locker is deffinately engaged. I think what may have happened is this:
While cleaning the cabs interior with some good ole' 2001, I may have pushed the switch in while wiping down the dash area. Then I may not have realized it was in and continued to drive it.
Any chance it could have shorted out some how??

 

First off you need to verify that your locker is engaged. The easiest way is to jack up one back wheel with the truck in neutral and see if you can spin the wheel.

I'll repeat this again Unless the first two conditions are met there is no way your locker will engage, simply depressing the button won't do anything. Besides if you did manage to engage the locker the light will be active.

 

Thanks for all the help folks...

I'll try all the suggestions, and see what I can find...
But lastly, does anyone know where the locker motor's fuse might be? I dont have a Haynes book for the truck yet, but I checked out the owners manual, and it didnt mention anything about the locker in terms of fuses.

 

First try jacking the truck up as Bruce suggested, and let us know if the locker is indeed locked. The only reason i think this is so critical is that what you are describing is VERY highly unlikely. Now, that doesn't mean that it isn't happening, or that you don't have a problem, but it helps when trying to figure out solutions to isolate the problem exactly.

If you're rear locker is locked, and you are in 4wd, there would be NO turning sharply. If that rear locker is locked, and you are on pavement, you'd be crabbing along, and the rear wheels would be hopping like crazy. It sounds like you have some hopping, are you actually having a lot? (i only ask becasue your above post doesn't really say how much, but just that it does.)

Next, just try unhooking the wiring harness from the transfer case while in 2wd, or whenever you are sure the locker isn't locked. Try 4wd. let us know what happens

 

sure enough guys...
JUST TO MAKE SURE.... I lifted one real wheel up, put it in 4wd HI, and neutral, and the wheel didnt budge. threw it back into 2wd, and it spun like a ferris wheel. I noticed today that when i engage 4wd, I hear what sounds like a puff of air. Does the e-locker work on an air pump?
I'm ganna go try to disconnect the harness right now... i'll keep you informed, as i am hoping for a solution to this crap.

 

How long have you had the truck? Have you ever been able to engage the locker and everything worked normally? (As in the Diff Lock light comes on, and the ABS light turns on.)

It seems like it would be theoretically possible that the locker's control box has somehow been tied into the 4WD sensor (aftermarket modification of course)... however unlikely it may be. Did you buy the truck new, or used? Did the truck come with the locker, or has it been added in?

Could you take a picture of the locker's contrtol module for us to look at, to see if there is anything suspicious going on down there?

Thinking about it, it's kind of an interesting mod that someone might have decided to do to their truck, sort of a faux grey wire mod.

(On another note, are you going to the U of A in Tucson? In any clubs?)

 

there is no air pump with these lockers they are electric

 

I go to Pima, not in any clubs... no time...

I think my only option right now is to buy a Haynes repair guide, and just work through the whole mechanism, until I can pin=point the problem. Once I figure it out, I'll post something, in case this happens to someone else. thanks for all the input.

 

I'm not sure Hayne's will be able to do much for you, but good luck!

Make sure to post a pic of your locker control box if you get the chance...

 

that doesn't mean anything. you had it in 4HI, locking the front and rear driveshafts together. you took one rear wheel off the ground. when you tried to spin that wheel, the resistance you felt was from the rear driveshaft being connected to the front (with both front wheels on the ground) via the XF case. you can't check for locker function that way. when it was in 2WD, the front and rear driveshafts were no longer connected via the XF case, so then when you spun the one rear wheel w/ the other on the ground, you simply spun the driveshaft which had no connection to the rest of the drivetrain since the trans was in neutral. you simply proved that your XF case was doing it's job and that you don't have a center differential. the 1999+ 4runners and all Land Cruisers are the only toyota trucks with an AWD system that is suitable for use on the pavement. Tacomas do *NOT* have a system that can be safely used on the pavement.

i personally think that your locker isn't engaging on it's own. you have 4WD, *NOT* AWD. if you try to turn in 4WD on pavement, you don't have a center differential, so you will get some binding in the drivetrain creating some slight wheel-hop and squealing.

to REALLY check the locker, put it in 4WD, the trans in Neutral, then jack up BOTH REAR WHEELS, then turn ONE of them. if you can't turn it, then the locker is engaged. if you can turn one, then your locker is NOT engaged and you're simply spinning the differential in the rear axle. you will feel some resistance in this instance, so don't expect it to free-spin.

 

I think Bamachem nailed this one squarely on the head... Have you been shifting into 4wd on the pavement and then driving around?

 

YOU ARE ABSOLUTELY RIGHT... I actually realized that while in class today (trig gets boring...). So i went out to the desert a while ago, and found a natural inclination ramp....(not sure why I didnt try this in the first place) locker is definately NOT engaging! and a tech told me the tires will chirp a bit in 4wd.

Now, I'm just praying that the RR DIFF LCK BUTTON is the culprit.
I had an alarm installed at the 'Specialist' about a month ago, and I don't recall if I had messed around with the locker since that occasion, so maybe they tripped something during the install..?

(I checked out the Haynes book- doesnt even mention the locker. WTH?)

So now I'm ganna take the dash apart (I guess?) and make sure the wires are connected to the button and what not. Know any easy ways of getting to the back of that switch?

ALSO, are there any fuses on the system that I should check? Like I said, the Haynes book didnt mention anything about the system, so I couldnt find any fuse locations.... a burnt fuse would be nice.

Thanks again

 

I pulled the switch out, but I dont know how to tell if it's burnt. Does anyone have access to the wiring schematics? Then, I can use a multimeter to tell if theres any continuity in the switch.