How To Trouble Shoot 4x4 Actuator

I took some voltage readings at the 4WD ECU. It is definitely getting power, and most of the voltage readings are in the correct range according to the attached diagnostics document (Pg TF-47).
I started on the top of the list with Terminal 12 to body ground: < 1 Ohm
Terminal 11 to 12: 12.42 volts

For the next two I wasn't sure if I was supposed to apply direct power to front ADD to get it in these positions or not. I did not do this but simply checked to see if the voltage changed when the 4WD dash switch was changed from 2Hi to 4HI position.

terminal 18 to 12: 12.13 volts, did change when switch was changed
terminal 19 to 12: 12.13 volts, did NOT change with switch position

terminal 25 to 12: Dash switch in 4LO (12.25 volts), in 4HI (0.67 volts), in 2HI (0 volts)
terminal 26 to 12: 9.91 volts (did not test while driving)
**terminal 28 to 12: This fluctuated continuously from 3.57 volts to 9.91 volts. When the key is first turned to on position it spikes at 11.5 volts.
**terminal 32 to 12: 4HI (0.67 volts), in 2HI (12.14 volts). Forgot to write down what it did in 4LO, but it is already very low voltage in 4H which does not correlate with diagnostics document.

For what it is worth I went to a salvage yard and swapped out the 4wd ECU to see if it changed anything. The 4WD and 4LO lights still blinked continuously when key was turned to ON position. Not sure if a different ECU would have to be calibrated to the vehicle first or not, any thoughts?

About to take it to the dealer to have them run through everything and see what they come up with. Any further advice before I do?

Thanks!

 

Had the dealer check the ECU and test for shorts in the wire harnesses. Tech said the limit switches for the transfer case actuator are either damaged or need re-timed. Recommended replacing the entire T-case actuator (Estimate around $2k). Any Input on how to ensure the timing on the limit switches is correct? Thanks

 

just ask them for a written guarantee that states if this 2k worth of repairs does not fix the problem you want full reimbursement

 

I have strong doubts that the limit switches are damaged. I want to get everything into the correct position so that the ECU stops causing the flashing 4WD And 4LO lights. But I need to know the best method to do so, and whether to start at the t-case actuator or the ADD actuator. I’m not willing to spend 2K for a potential fix, I would just upgrade to an FJ Tcase at that point.

 

my .02, start at the ADD

all of my issues have seem to have been ADD related

i know how you feel though, this is beyond frustrating to diagnose

 

Update for ECU testing:

I tested the TL1, TL2, and TL3 terminals in the ECU, which should correspond with the limit switch positions in the transfercase actuator. All had readings of 12.6 volts, which contradicts what should be occurring, at least according to the 4wd troubleshooting PDF I posted earlier. I tested the terminals at the transfercase actuator, and they were demonstrating the proper readings for the 2Hi position (continuity for the appropriate pin, no continuity for the other two pins). Does this suggest a problem with the ECU? Starting to bang my head against the wall from this problem, as a dealer tech I spoke with could not give me solid answers. Thanks for the help.

 

TL1 should be reading 0 volts in 2hi. Sounds like your actuator limit switch is toast, you can replace that fairly easy, unfortunately no aftermarket solutions, your best bet is to find a junker and swap it out. Please see attached for some additional references. Should be pretty simple, take all the readings, see what doesn't match. The t-case actuator engages first followed by the front ADD actuator. The 4hi position switch on the t-case is what tells the front ADD to engage, so if that's bad, you won't get the ADD to ever attempt to lock in.

 

That was my first thought, however I just replaced the Tcase actuator with one I found at a salvage yard. I ensured that the limit switches were in the correct position, and I even tested them in multiple positions to make sure they were reading as they should. I tested them at the pins on the Tcase actuator with it out of the truck and also while installed.

Is it possible that either a short is occurring in the wiring harness, or even that the ECU is bad? Any recommendations for testing the ECU? If I install an ECU that I salvaged, does it have to be calibrated?

I am posting from my phone, so if that info is in the attached docs you provided I apologize. Will read them thoroughly after work. Thanks for the info!

 

Interesting, well there is a thought then that a pin on one of the connectors that goes into the t-case actuator and/or 4wd ECU could be loose or disconnected, or the wiring in between the two connectors are frayed somewhere.

No testing procedure for the ECU but if you verify the voltages are all good feeding back to the ECU, then that would be your last failure mode you could replace it. The ECU is readily available and in my experience almost is never the problem. It does not have to be calibrated, if you need one I have one I can sell for cheap. They are a very simple device, a couple relays and transistors that switch on and off the motors.

 

Thanks for the info. Are there different versions of the 4WD ECU and do I have to ensure it is compatible prior to switching out? I'm going to double check the wiring when I have a day off, which is not this week. Depending on the cost I may just buy the ECU from you and replace it to see if that resolves the issue, before crawling around and testing all the wiring harnesses. Let me know a price, thanks again.

 

I have an additional follow up question. So when I tested the TL1, TL2, and TL3 wires at the ECU, I tested them with the wiring harness attached to the ECU. All had voltage readings about 12 volts. I removed the wiring harness from the ECU, but left the other wiring harness attached (the one that supplies the power and ground to the ECU). I tested the appropriate pins in the ECU for TL1, TL2, and TL3 (while the wiring harness was disconnected), and they all read above 12 volts. I repeated both of these tests after unplugging the wiring harness to the Transfer case actuator, and all results were the same. Does this point to a problem in any specific area? Thanks

 

I don't believe that is a valid test. 12V is sent to each of the TL1, TL2, and TL3 pins all the time, once those limit switches make up in the appropriate position (2wd, 4wd, 4lo respectively), they send that 12V to ground, the ground is supplied through the transfer case actuator harness. That in turn signals the 4wd ECU logic that the limit switch has changed position. Doing the test with the harness unplugged will give you erroneous results. You want to do the voltage tests just as the truck is performing normally with all the harnesses connected. Get a DVM with long pointy leads like the one in this picture, or use a paperclip to probe the back of the connector to get a voltage reading while the connector is still in the ECU.

I believe there are differences, for example if you have an elocker or not. Mine is out of a 2010 TRD offroad it's actually still in my truck. I installed an FJ case many moons ago due to my transfer case actuator taking a crap, send me a PM and let me know I can probably get a P/N off it if I remove it from the truck, and you can check to make sure it will work for yours.

 

Hi all-

ive been following along trying to troubleshoot the same symptoms as Heineken:

wont switch out of 2wd, 4hi light on constant, 4lo light blinks constant, beeps if dial is switched out of 2hi

i just had it back from the dealer, they told me the front actuator is bad(i took it in for the frame spray so had them run diagnostics while it was there).
prior to taking it in to the dealer, i pulled the ADD(bench tested) and did the solder fixed that has solved it for many others with no luck

i have now ordered a new ADD to replace it. does anybody know what the OEM part number is?

i am at a loss and i am not convinced a new actuator will fix it.

i will report back once i swap it out, if it doesnt work i will move to the next thing i guess

 

41400-35032

Good luck

 

@6 gearT444E


thanks for your response. i got the new actuator and i was going to solder the leads for some preventative maintenance.
one question i had was we re-assembling the unit...is there any trick to it? there is a little switch opposite the motor...where does that get lined up? can i put it back together incorrectly?


any help would be great

thanks in advance for your time

 

that’s the switch to let the 4wd ECU know the ADD is engaged. It’s actuated by a cam on the gear drive. As long as you take it apart and put it back together without moving the worm gear it shouldn’t require any tinkering with.

 

i think i moved the worm gear (mad at myself!)

if its in 2hi currently... should the arm be all the way to the motor side or to the breather hose side?

looks like i only have clearance to drop the cam below the switch if the fork is halfway through its travel...does that make sense?

 

EDIT***

 

I replaced the front actuator and it did not fix the problem.

now the 4hi and 4lo lights blink simultaneously (and at a higher frequency) as opposed to before when the 4hi light would be on and only the 4lo would blink.
also there is no beeping noise anymore like there was previously when switched to 4hi.

i am at a complete loss as to what could be at fault.

if there is no voltage reading at pins 1 and 2 of the harness to the actuator, where do i look next?


any help would be greatly appreciated and thanks for your time in advance.

 

2008 Tacoma Double Cab TRD Sport. 240,000 miles. US truck but I imported it to Canada in 2009.

4WD has been great, use it every winter, but don't think I've ever used 4Lo ever. Long story short, my son borrowed the truck and went offroad and although he said he only used 4Hi, it's now blinking and stuck in 4Lo.

This thread has been great. I removed my 4WD Actuator, and honestly I think I have the record for the worst condition actuator in the history of this thread. Check this out. The plastic case had a couple mm gap and the screws on the corners had cracks in the case under them:



Don't ask how it possibly got this bad, I don't know. It was under the skid plate and protected from any physical contact so I don't know what split the case.

So I ordered a new unit from RockAuto, and I'm about to install it today. Here's what RockAuto had available at time of order:



I chose the Standard Motor Products, it was $60 cdn more than the Aisin part.

Here's what I received:



Now I'm wondering - did RockAuto screw up, or is the Standard Motor Product version just the Aisin with a longer warranty? If you check RockAuto, the warranty on the Aisin is 12 months, 12,000 miles whereas the Standard Motor Products warranty is 36 months, 36,000 miles.

Figured I'd post this info in case it helped anyone else - certainly seems the two are the same part, in which case you're just paying extra for warranty if you go with the Standard Motor Products p/n.

My truck is currently up on steel ramps in my driveway. If I reach in and try to move the collar that the actuator engages - I can't. It seems stuck pretty good.

Is this normal with the wheels not free to spin? Should I be able to move that collar with it up on ramps to disengage the front diff? I'm curious before I install the new part and refill my fluids that I could be wasting my time if that collar is supposed to be easy to move by hand.

The other question I have is - notice in the RockAuto screenshot above that they list an Aisin replacement part now for the rear diff as well. I haven't seen anyone talking about this. Has anyone tried the Aisin replacement on the rear? I haven't had a look at the rear for mine yet, figured it was obvious my front actuator had to be swapped before I tried anything else.

colins