4wd System Operation & Help Thread

TnShooter. I will remove the skid plates to access the ADD on Friday & report back.

DM93. I thought I did.

I still have the original ADD. I replaced it with a unit from NAPA.

 

I have no power at the green/black wire with key on and disconnected from ADD.

 

I just removed it and the fork was in it's position on the collar correctly.

Hooked up my original ADD and tested the Green/Black wire and I am still seeing 12vdc on the wire at the ECM. All other wires have the same on values as the replacement actuator.

 

If you have 12v at the ECM, but not at the ADD plug. That is your problem.
The wire is broken somewhere.

 

I'd check around by the EC1 connector above the front axle, seems relatively common for the wires to break/corrode in that area.

 

Thank you so much. Found broken wire within 6 inches of the jumper plug connection.

Also to remove the top 2 screws I HIGHLY recommend purchasing a Snapon Indexing Handle 1/4 drive fine tooth ratchet. It make the job alot easier of installing & removing the top bolts on the ADD.

 

Nice, glad it was an easy fix.

Dang they are proud of that thing, $175 for a 1/4 in ratchet. I don't need it that bad lol, I have a set of 4 GearWrench 120xp flex heads I paid $90 for (they are now around $145). Love those things.

 

The I got it for $150. The Snapon rep comes to the Heavy equipment shop i work at.

 

First time chiming in here. Been having the issue of 4lo light blinking on startup, luckily this started to happen while in 2H but the weather is starting to change where I live so I gotta get this thing working. Issue started over the summer. 4lo light would randomly come on, then never seen it for weeks. As of a few weeks ago, almost every second time I got in my truck, I would turn the key before starting just to check and sure enough, 4lo blinking. Now its blinking all the time...

T-case is in 2H for sure, 4wd switch in 2H, front driveshaft free, inside t-case actuator looks fine, limit switch inside t-case is set to the correct position (according to here) but voltage on TL1 and DL1 at the ECU are both 12V when they should be 0V while in 2H. All other voltages in the 2H column fine. Also getting continuity through the TL1 and DL1 while both plugged in to ECU and unplugged. However, if you unplug either the t-case or ADD, continuity is lost. I'm starting to guess that maybe the ADD actuator limit switch might be stuck in the wrong position. Any thoughts?? Not sure what else to do at this point

Both t-case and ADD actuators worked up until the dreaded 4lo blinker started blinking constantly. They both worked so long as 4lo wasn't blinking. Also, yes the t-case actuator is working. I also swapped it with a known working one but still having the same issue.

 

It sounds like a ground issue to me.
In order for the voltage to show 0v. It need to be grounded.

Unplug the transfer actuator and see if you have continuity to ground on the White/Black wire.

Or better yet.
You can also see if you have 12v when you test the Blue/Yellow and the Black/White wire.
Place one of the meter leads on the Blue/Yellow wire, and the other to the White/Black.
It should read 12v

Key ON for the test.

I prefer to use a test light hooked to battery power to test it.

 

That would seem plausible being both are at 12v, @aurom709 do you also have EVAP codes and does your cruise work?

 

As I was falling asleep I thought of the same thing! I will have to try when I get home from work. Thanks a lot btw.

I already checked the ground behind the cylinder head on passenger side. Any other places I should check?

 

No EVAP codes and my rig doesn’t have cruise control. Looks like I will be chasing around a ground issue lol

 

The reason I asked is all that is on the same ground tree.

 

Maybe another case of the junction box ground failure. I hope not. I mean it’s not a huge deal. But no one has figured out exactly where it “breaks”.

Worst case we can make a new ground.

We will see when he gets back to us.

 

With my luck, that’s where the problem will be lol. I should change my last name to Murphy.

I had a long day at work and the weather sucks today, so looks like it’s a tomorrow problem. I will get back to ye and let ye know if I find the problem!

Thanks a lot guys! As an electrician, this problem has me addled but it’s mostly because I don’t know any other mechanically inclined Taco owners to just bounce ideas off of. Plus DC power just throws me for a loop every time because with AC power, ground is always green.

 

I under stand that....
The ground issue isn't a huge deal.
If it doesn't make it back to the Junction Box, Just crimp on an eyelet and ground it under the dash.

But let's not get ahead of ourself. Test for voltage and ground at the actuator first.

 

There's plenty of us here, you just have to ask.

Electrical theory is still the same just DC only flows one way.
Toyota pretty much exclusively uses White/Black for ground wires and Brown for sensor ground. I won't say they may use other colors but I've yet to see a White/Black wire that wasn't a ground on a Toyota product.

 

Good to know! AC is all I ever deal with, usually, so the green = ground thing is always at the forefront for me. I just have to sometimes tell myself “this is DC not AC” so I stop trying to test everything to a green wire.

Just did a quick test at the ECU while I went to the store. Looks like I have 12v to ground at both t-case and ADD. Yes, the white/black wire lol.

 

Well I guess we need to check them at JB No 2 behind the glovebox but I guess we could do a quick check between pins 4 & 5 of the DLC although since you don't have a CEL I suspect that will be good.

Note the DLC is upside down on 2nd gens.