Front diff lock isn’t engaging

[ppc]

I’m coming around to going with the CDL permissive (It’s been awhile since I really have ran my lockers, TBH, that & that concussion I took) - but the big picture is that the CDL/ trans case locker is really accessible unless you’re armored to the hilt under there.

The sensor plug you need to jumper looks just like the 2 pole one on either axle locker, all 3 confirmation switches are the same & interchange.

I will add that IIRC you get both the ABS light to flash as well as the CDL light in the cluster when yu get it working/jumper the plug - both bulbs being burnt out is slim / none. (That is right, yeah @ppc ?? - correct me if I “whiffed” another one.)

Absolutely correct Linus.

 

[Mr Cimarron]

Yup when I got my sorry excuse of a maintained 94 from the PO this was the first thing I did in trouble shooting the lockers, paperclip diagnostics! I ended up needing two of the switches which also turn out to be pretty much standard Toyota reverse indicator switches and only $20 at NAPA.

I learned after I converted to the split case and realized it was the switch that mattered. When I had the switch go out I made a jumper so my lockers would still work while in Moab.

 

[Mario12345]

I’m coming around to going with the CDL permissive (It’s been awhile since I really have ran my lockers, TBH, that & that concussion I took) - but the big picture is that the CDL/ trans case locker is really accessible unless you’re armored to the hilt under there.

The sensor plug you need to jumper looks just like the 2 pole one on either axle locker, all 3 confirmation switches are the same & interchange.

I will add that IIRC you get both the ABS light to flash as well as the CDL light in the cluster when yu get it working/jumper the plug - both bulbs being burnt out is slim / none. (That is right, yeah @ppc ?? - correct me if I “whiffed” another one.)

So what your saying is pull the senswer switch wire from the cdl and connect the two then see if the front diff locks

 

[LINUS]

So what your saying is pull the senswer switch wire from the cdl and connect the two then see if the front diff locks

Yes. “Fool” the body harness into believing the CDL is engaged.

If you tripwire the body harness via that socket, it should open the permissive of axle lockers, provided you put the transfer case in LO range & we’re not playing around with any CDL switch.

If you come back to the LO range functions as a basic, let the 80 eo all it wants with plenty of battery charge - then shifting the TC to LO & fooling the vehicle wiring harness with that plug jumpered should allow axle lockers to be available.


At that point you know then it’s that switch (Napa PN is in other threads) - is just the fault, and if you can’t “fix” yours by unscrewing & using solvent to fix it, you buy a new one for ~$20.

And might as well buy a 2nd since they crossfit into the TC, FR & RR lockers as the position switch. Exact same part.

 

[Cruiser Ed]

so I checked the actuator with the 9 volt battery test and it worked I guess from the nosies it made.... but now I also removed the harness and checked it and found nothing wrong with it ........... so now I guess the next step is to tear out the radio and start tracing wires f*** my life

Hey Mario, did you check the inside the wire loom or just the general condition of the wire? I did what Linus suggested and used a continuity meter to check sections of the harness. I found a break in one of the wires of the rear locker. I've never seen a wire break/corrode inside of the loom before so anything can happen.

Locking Differential Just Blinking

 

[Mario12345]

Hey Mario, did you check the inside the wire loom or just the general condition of the wire? I did what Linus suggested and used a continuity meter to check sections of the harness. I found a break in one of the wires of the rear locker. I've never seen a wire break/corrode inside of the loom before so anything can happen.

Locking Differential Just Blinking

Yea I’m not to good with the continuity thing so i said screw it and ripped the loom off abs replaced it but i mean worth it any way because it was covered in crap on inside, i just don’t know where to start for the continuity test, meaning the beginning connector plus i don’t have a tester that long for continuity if have to remove whole harness

 

[Mario12345]

Yes. “Fool” the body harness into believing the CDL is engaged.

If you tripwire the body harness via that socket, it should open the permissive of axle lockers, provided you put the transfer case in LO range & we’re not playing around with any CDL switch.

If you come back to the LO range functions as a basic, let the 80 eo all it wants with plenty of battery charge - then shifting the TC to LO & fooling the vehicle wiring harness with that plug jumpered should allow axle lockers to be available.


At that point you know then it’s that switch (Napa PN is in other threads) - is just the fault, and if you can’t “fix” yours by unscrewing & using solvent to fix it, you buy a new one for ~$20.

And might as well buy a 2nd since they crossfit into the TC, FR & RR lockers as the position switch. Exact same part.

IM going to try this today and I’m not sure if i said early my abs light was burn out but it’s not i meant i thought just my cdl light was my abs light won’t shut offf so that bulb was removed and in the process i saw there was burn marks on the back of the cluster in a few spots but maybe it’s not bad. I REALLY APPRECIATE YOU ALL NO LIE THANKYOU HOPEFULLY THIS FREAKING WORKS . There’s snow by me and I’m trying to get in it sooner then never

 

[Mario12345]

Yes. “Fool” the body harness into believing the CDL is engaged.

If you tripwire the body harness via that socket, it should open the permissive of axle lockers, provided you put the transfer case in LO range & we’re not playing around with any CDL switch.

If you come back to the LO range functions as a basic, let the 80 eo all it wants with plenty of battery charge - then shifting the TC to LO & fooling the vehicle wiring harness with that plug jumpered should allow axle lockers to be available.


At that point you know then it’s that switch (Napa PN is in other threads) - is just the fault, and if you can’t “fix” yours by unscrewing & using solvent to fix it, you buy a new one for ~$20.

And might as well buy a 2nd since they crossfit into the TC, FR & RR lockers as the position switch. Exact same part.

Also should i do it on dirt or just switch it see if it engages drive forward a little and back up to see if it locks. I know it’s not nesassary to move but.... how’s that sound
???

 

[LINUS]

^^^^I’d throw some cardboard to lay on & your tools in back & go do it on a gravel lot personally - but fooling the body harness and listening to see if your solenoid/ relay kicks can be done in your garage/driveway without even running the motor.

If you can get positive “signs of life” (sounds really) - then the cardboard / tools in back & a gravel lot would be my next step. You may still need to do more diagnostics
beyond jumpering the position switch socket at the TC.

 

[Mr Cimarron]

All it takes to get the locker to lock is raise jack one wheel off the ground and rotate by hand. When it locks it will stop moving. All can be done in the garage without the truck running. No need to get dirty during testing.

 

[Mario12345]

Also should i do it on dirt or just switch it see if it engages drive forward a little and back up to see if it locks. I know it’s not nesassary to move but.... how’s that sound
???

Just so you know ... i ****ing love You ! Hahaha now i need to just go to autozone and pray they have the switch /sensor

 

[LINUS]

All it takes to get the locker to lock is raise jack one wheel off the ground and rotate by hand. When it locks it will stop moving. All can be done in the garage without the truck running. No need to get dirty during testing.

Not so simple. Axle lockers, sure - but if he’s working the CDL at a minimum you need 1 tire of each axle off the ground, and even then you’re relying on the open axle diffs to spin.

I know I have it easy with a hoist, but I’d personally want jackstands on the axles at all 4 corners so I could test everything in the system with the tires just off the ground. Esp since the differing design of the lockers means there’s a lot of lag between when each axle will really lock up.

At any rate, if the CDL locks with just a single tire off the ground, the 80 is going to jump forward if the motor is running. Gotta have 1 per axle minimum.

 

[Rifleman]

I found a break in one of the wires of the rear locker. I've never seen a wire break/corrode inside of the loom before so anything can happen.

It's not as crazy as you might think to have a wire break inside a harness. On 94 LC The front locker harness loops down from the fender right pass the hot exhaust. The heat from the exhaust can cooked the insulation on those wires. In my case it caused some of the wires inside my harness to snap in two.

 

[Mario12345]

Not so simple. Axle lockers, sure - but if he’s working the CDL at a minimum you need 1 tire of each axle off the ground, and even then you’re relying on the open axle diffs to spin.

I know I have it easy with a hoist, but I’d personally want jackstands on the axles at all 4 corners so I could test everything in the system with the tires just off the ground. Esp since the differing design of the lockers means there’s a lot of lag between when each axle will really lock up.

At any rate, if the CDL locks with just a single tire off the ground, the 80 is going to jump forward if the motor is running. Gotta have 1 per axle minimum.

Any chance you got the part number

 

[LINUS]

It's not as crazy as you might think to have a wire break inside a harness.

+1 - I’m surprised we don’t see more of the axle pigtails being the culprit of bad axle lockers. Between being relatively fragile compared to any other wires hanging down there, the fact we all run over downed branches & general articulation over the last ~20yrs, I bet we start seeing more of them as the issue.

At least the OP found his issue - and as a “you never know” - pull the sensor & give it a good bath in WD-40/similar & exercise the ball/spring. It could be a free fix.

 

[Mario12345]

+1 - I’m surprised we don’t see more of the axle pigtails being the culprit of bad axle lockers. Between being relatively fragile compared to any other wires hanging down there, the fact we all run over downed branches & general articulation over the last ~20yrs, I bet we start seeing more of them as the issue.

At least the OP found his issue - and as a “you never know” - pull the sensor & give it a good bath in WD-40/similar & exercise the ball/spring. It could be a free fix.

True but I’d rather put in a new part and not worry you know ?!!?

 

[LINUS]

Napa part number: NS6421

At least that is the one for the front locker, but I think they're all the same.

A quick search & got this ^^^ - I just took the whole post.

They are the same for all three places, so when you pull that old one see if you can fix it, toss it somewhere for a spare.

 

[Mario12345]

A quick search & got this ^^^ - I just took the whole post.

Thankyou !

 

[Mario12345]

Big shout out to everyone that helped ! Thankyou all so much this was driving me nuts

 

[allan man]

Glad you got it worked out... its a good feeling isnt it.
Love this type of discussion on the forum with everyones opinions you are able to help fix
Someones truck and learn at the same time...win win!