4wd System Operation & Help Thread

Your certain all the limit switch voltages are correct when the lights are flashing?

 

with the truck in 2hi and key on. i backprobed all the pins on the list twice and every voltage lines up with expected values. I didnt try switching to 4hi or 4lo and testing those values i only tested the 2hi column. When i had issues with dl2 value earlier i bought a new aisin front add as i thought that indicated faulty add. the add will be here in a few days so i can try swapping that out. to me everything is lined up and the voltages all line up. i dont understand why it wont clear

 

If the voltages are indeed correct the light's shouldn't be flashing, I guess it's possible the 4wd ECU has failed but I've yet to see one go bad.
you don't happen to accidentally have an old copy of the pin chart? The reason I ask is I had a typo on the printable chart that was found and I corrected recently.

Maybe check everything in 4H again and make sure.

 

I think it is the updated chart as i read the comment you made saying you fixed it in the initial post and i printed it off after that. However i will check after work

 

I don't know if you saw it or not but I did recently add pictures of the connectors with labels you can use to verify your on the right wires.

 

Yes the actuator is supposed to show up tomorrow and ill test it out. i believe i have the newest information printed out. the truck is definitely taking longer now to start flashing both lights almost like it passes more checks then before, before it finds a fault. I'll test connect the actuator and then retest all the voltages.

 

Well heres the latest. plugged in new actuator without fully installing it. I did test it with the metal portion touching grounded metal on the truck in case it grounds out that way at all. testing showed it was in 4wd position. powered the motor plug connections. cycled it to 2wd position. retested. test 1 and test 2 were with the old actuator after i retimed it to be correct. test 3 is when before i moved new actuator out of 4wd. test 4 is actuator in 2hi position. All the voltages seem correct but still just instant flashing 4hi and 4lo lights. also upload a copy of chart im using for identifying when to backprobe. all testing done with key on. all actuators plugged in and 4wd ecu plugged in. dash switch in 2hi position truck in park.

 

All the voltages being correct and still having the lights flashing I can't see what it could be besides a failed 4wd ECU, first time I've seen it though.

Any history to when this started like a dead battery, reverse jump start, or possibly lightning?

Maybe pop the 4wd ECU apart and see if there's any apparent damage.

 

I did pull ecu apart a few months back to check. and it seemed fine . no obvious damage. it all started when i pulled front actuator to solder motor connections. 4wd worked before then with no issues. after i soldered front actuator motor pins i pulled transfer case actuator cover in case there was a motor there to solder 2. i left shaft and small gear in place just pulled black plastic cover part and when i did that the gear with the prongs fell out. and no matter what ive tried it, like realigning gear prongs to swapping parts hasnt worked since. that was probably 3 years ago .

 

I can't see any other reason for the light's to be flashing with all the voltages being correct.

 

Well i bought a used 4x4 ecu off ebay. it arrived today. i turned key on with old ecu lights flashed. turned key off. plugged in new ecu and lights were clear immediately and everything functions as its supposed to. So it definitely looks like it actually was the ecu even though it looked fine no damage that i could see anywhere. Thanks again for all the help. Ive been fighting this since at least nov 2021.

 

Glad you got it fixed, it's definitely the first case I've come across of the 4wd ECU failing.

 

Hey again
So i think my front
diff actuator motor is fried.
Am i thinking right that by applying 9v at pin 1&2 at front diff actuator it should move the arm position?
Im trying this with actuator on truck.

 

It should do something, you may have to reverse the polarity to get it to move the right direction but it should move with 9v I would think.

 

Thats what i thought!!
I get nothin i tried reversing too
Damn i didnt want to have to pull that actuator out again..

 

Is there a right up this good for third gens? Our 4wd ecu is different

 

The 3rd gen system can talk to a scan tool that is capable of communicating with it so that would be my first step.

There is a thread on the 3rd gen system, they don't go as in depth on testing as I have though. The operation of the 3rd gen system is almost identical to the 2nd gen system but obviously wire colors, connectors, and locations are different.

3rd Gen 4x4 https://www.tacomaworld.com/threads/4wd-actuator-troubleshooting-transfer-case-and-add.578262/

 

Thanks man. That pdf will help me figure out what wires are what. I’d imagine the voltages are supposed to be the same.

I have replaced ADD, 4wd subharness and at this point I’m about to swap in a buddy’s known good ecu. After that I’m not sure what else to do… error code is p17a4 but I don’t have tech stream to pinpoint anymore than that.

 

Looks like the ADD uses the same configuration as 2nd gens, the Transfer Case Actuator configuration looks a bit different though.

You should be able to look at scan data and see the condition of the switches.

 

Don't need one yet but has there been any discussion of the quality of the various aftermarket transfer case motors?

If these work and last 1/2 as long as OEM then at 1/10 the price they are a bargain.

I have seen prices as low as $140 cdn up to $2000+ from the dealer. To me this seems like a part that wouldn't be that easy to replicate in the aftermarket but that just my opinion. When i used to have a BMW i was able to buy the actual Bosch electrical parts alot cheaper because the didn't come in a BMW box.

And like a lot of parts maybe this is actually made by AISIN or one of these aftermarket companies and just marked up greatly by Toyota.

Just like we all know Toyota Genuine Motor Oil (TGMO) isnt made by toyota...


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