4wd System Operation & Help Thread

@Dm93, @TnShooter

Below are my measurements and my post review comments.

1. No issues with 2WD. Voltages check within range. TC actuator rod is in the correct (fully forward) position.
2. 4HI is throwing two errors.
   2.1 The TC shift rod appears to have moved because TL1-TL3 are at the correct voltages. I conclude the TC actuator did in fact move the rod back one position to 4HI.
   2.2 4WD is 0.0v saying the system is in 4WD. Plus L4 agrees with spec (13.x VDC), it is NOT in 4LO (meaning the TC rod did not move out two positions, only one).
   
   DL1 and ADD circuits in the ADD actuator did not move. They are identical to 2WD voltages. I conclude the ADD actuator did not move the yoke because DL1 did NOT go to 13v and ADD detection switch did not close to 0.0 (gnd). Could my new Dorman ADD actuator be bad out of the box ?
   
   
3. Engaging 4LO had multiple failures.
   4.1 Looking at TL1-TL3, they are identical to 4HI values. Plus L4 never dropped to 0.0 telling me the TC actuator never fully put the TC yoke arm into 4LO. If fully engage in 4LO, the L4 switch would be fully closed and value would be 0.0 (gnd). Instead, L4 is 13v, telling me the TC rod has not fully extended out of the TC into 4LO position.

Conclusions

1. 2WD appears fine, based on voltages.
2. It appears the truck's TC actuator is in 4HI but the ADD actuator is not engaging, powering the front wheels using the TC.
3. It appears the truck cannot go into 4LO because the TC actuator cannot pull the rod out further to 4LO position. Likewise, the TL1-TL3 values do not change as well as the L4 switch does not close. This tells me the (1) the TC actuator motor stopped working from 4HI to 4LO or (2) The L4 TC switch is broken in the open condition (always at 13v) and the 4WD ECU will not allow the TC actuator to shift the rod further back because L4 never goes to 0.0v

Actions: ?

1. Test 4L switch in the TC actuator. If bad, replace it. Spend $60 on a new L4 switch.
2. If 4L switch is good, remove TC actuator and replace with a new one. Spend $250 on a new TC actuator. Retest
3. If truck is still throwing errors, replace TC with a rebuilt unit. Spend $2.5k

 

Shifting into 4LO cannot occur because it never knew it was in 4HI mode. Given your transfer case detent and limit switches operated SAT, and the news that you have a poorman ADD actuator, that’s all I need to know. The poorman stuff is junk. Put an OEM back in and your problems will be resolved.

 

If it's a Doorman it wouldn't suprise me if it's dead, at the shop we call it dooman because much of their stuff is junk.
You can put a test light across the DM1 and 2 terminals to make sure it's getting power to move when switched to 4wd.

 

I have not gotten a chance to read the whole post. I am in the field working on a fence.

But I will 2nd, don’t buy Doorman.
And if you do, only as a last option. And maybe buy 3. Put the 1st one on. Then immediately remove it. Throw it away. Because it was BAD out of the box. Put 2nd one on. Then save the 3rd one for 6 months to a year later when you have to replace the 2nd one.

 

Yes, I beginning to think my doorman is really a dog-dump.

tomorrow i’m taking it in to the dealer and having the ADD actuator replaced with a factory unit.

 

You might do as @Dm93 said, just to confirm you are getting power to the actuator. While I do agree that OEM actuator is the best. The dealership is definitely gong to be expensive.

If you are just paying them to Remove/Replace it will be expensive.
It will be even more expensive if you have them “diagnose” it too.

Most dealerships in my area will not remove and replace with out first doing a diagnostic. But smaller independent shops will, of course with no guarantees.

 

Yup, I asked my service advisor to measure DM1/2 at the ADD to see if power is there.

 

Follow up:

Replaced the dog-dung (doorman) ADD with a genuine Toyota pn. Replaced the transfer case actuator with a genuine Toyota pn.

Everything works now. Showed the mechanic how to replaced the transfer case actuator by pulling the pinion gear and leaving the shift rod in the case. Saved major $$$.

The transfer case actuator was iffy: I decided to replace it at the same time with the ADD actuator. Failed once, but we couldn't get it to fail again.

I need my 2007 Taco to last another 15 yrs.

 

Just Figured I would mention that all of my 4x4 issues are still around, however I am on deployment so cant work on it. hopefully the 1200 dollars in actuators i ordered from Toyota solve my issues. If it doesnt work Im pretty set on this being the last straw before the truck becomes someone else's project

 

Good luck, keep us posted

 

Sub'd. This accurate, condensed, detailed summary kicks ass. This one post is worth as much or more than 39 pages of random troubleshooting remarks in another 2nd gen 4WD actuator thread. I wish the internet had a button you could push that says "pay the content creator $5 instantly." My 2014 TRD-OR 6sp MT 4WD system is working fine so far (at 63K miles, with very little off road / wet usage) but it's great to understand at maximum detail how the entire system works so I know how to troubleshoot effectively if need be.

 

Thanks for the comment, I did the best I could with the information I could dig up and by testing things on my own truck although I have never personally gotten the opportunity to diagnose one myself.

I have the exact same truck and I'm at 66K, no issues yet either.
Keep an eye on those vent hoses, they are the source of many of the 4wd problems encountered on our trucks.
Also engage it from time to time whether you need it or not to keep everything working.
Here's to many more trouble free miles

 

Good day, I'm new here and I love all the information on Tacoma World and Taco lover!

I do have a similar problem with my TRD OffRoad 2006 Automatic (170K miles), the 4wd and Lo flashing on display. I followed most of the info here, very well documented! I did remove the ADD, cleaned and inspected, well lubricated with dielectric grease, and it worked for about a week. Then the flashing started again.

Now, the interesting part is that I had a Check Engine (not related to the 4WD problem or the ADD, as I found out and with your information thank for the info that it cannot be read with a OBD) but other snags came up (Misfire, MAF sensor, And VSS Malfunction, TR Sensor, and Speed Sensor Unit) BUT !! when I plug in the OBDII in the slot the 4WD/Lo light went away! then plug out the Innova, and lights came back, then hook up again light off. Even with the Innova computer NOT hooked on. Just the OBDII Connector cord plug in !? Light went off !?

I am wondering if the OBDII Connector on the Truck side side, would cancelled (ByPass with just the connector) one of the signal that would prevent the ECU to give the command to the ADD.

I had codes (P0500, 705, 717 and 722) which I deleted. But the 4WD Lo Lights are still flashing on normal configuration

Wonder if the PCM should be reloaded at the Dealer after those codes being deleted?

My best regards

Steph

 

Based on what you described I suspect you have a bad/loose/corroded grounds at ground point EE (rear of passenger side cylinder head).
What happens when you plug a scan tool into the DLC is most scan tools jump pin 4 (Chassis Ground) to Pin 5 (Sensor Ground) thus in your case providing another path to ground for all the affected sensors.
I would take a good look at all the ground wires on the back of the cylinder head and also give them the tug test if you don't see anything visually.

 

Thanks man for your swift response! The ground was already removed, been cleaned with scotch write and gave a crimp on terminal (with plier) to make sure of contact. I could maybe put a jumper cable on terminal with alligator clip, just to make sure.
Maybe I should try to check Voltage on the ECM with the OBDII connector plugged in.. to see If I have same voltage from the switch (B12-13 and 26)?

 

Have you check the grounds on the DLC?
That would be where I’d start. Just to be certain your are in fact missing a ground.

 

Some branches of that ground tree also go through the passenger side interior junction box and engine harness to dash harness connector on the passenger side IIRC, I don't have time to track down pin numbers and locations right now.
You could check pins 4 & 5 of the DLC in reference to battery ground with the key on and see what kind of voltage drop you have (I suspect there will be quite a large voltage drop between pin 5 and battery ground).
The key info for me is that you say everything works properly with a scan tool connected, that makes me suspect a bad ground.

 

What are you calling “B”?
This?

 

Good day to all,
The "B" is the Pin number on the ECU Pinout
DL1, DL2 and ADD. for the switches

as for the DLC

Battery stand at 12.2 V
Pin 4: 11.26 V
Pin 5: 10.56 V

You are right, might be one of the grounds. I did check the EE one and cleaned it up. Will have to go and check others one by one and clean them. I wonder if they would be a common gnd from the Speed sensors or the TR sensor with that circuit? It might lead me to another ground? Would have to check out wiring manual.
I live in the country side, lot of snow and mud, also, my Taco got a new frame a year ago (Toyota warranty is amazing), and since then, always had a "cluck" when going to 2WD to 4WD to 2WD. Rust is building up under both access door rocker panel too.. Need to take care of it, she's good to me!

 

When I said check the pins in reference to battery ground I meant one end of the meter on battery ground and the other on each pin 1 at a time but nonetheless it looks like you do have a bad ground somewhere.
Since you said the frame has been changed I would do the same test for the main grounds, engine running 1 end of the meter to battery ground and the other one at a time to the engine block, body, and frame and see what your results are there. You should see no more than about 0.3v.