4wd and 4Lo lights flashing

When I try to put my truck into 4wd I can hear the 4x4 ecu behind the dash click but nothing engages then the 4wd and 4Lo lights just start blinking. I turned the dial back to 2wd and the 4wd light and 4Lo light continue to blink. I had issues with my transfer case actuator but I replaced that and it worked fine just a month ago. Does anyone know what this issue could be?

 

Not trying to be a dick but theres multiple very detail threads(with pictures, schematics and videos$ pertaining to this issue. I know the search engine on the forum is not the best so I encourage you to type your thread title on Google followed by Tacomaworld you’ll get all the goods. Cheers!

 

https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

I’ve searched endlessly but I cant seem to find a thread that has the same exact issue as me. I’ve seen some that say loose connectors could be the culprit but I haven’t been able find where those connectors would be.

Edit: I read it can also be the switch itself but since I’m hearing clicking in the ecu I’m assuming it’s not that

 

Each case is different, what may fix one truck might not fix the next. There is no silver bullet fix for the 4wd system on 2nd gens.

The easest way to pinpoint the part of the system that is causing the issue aside from a quick visual inspection of the vent hose and wiring at the actuators is to check the limit switch voltages at the 4wd ECU as outlined in the thread I posted above and see which one(s) are out of range.
Do that and report back with your results and we can help you, without doing that anything else is a guess.

 

I’ll try to get to that by this weekend, before today I could turn the truck off and on repetitively and the transfer case actuator would eventually make a sound then the 4wd would work and the flashing lights would go away , same process for getting it out of 4wd. I’ve tried that same process today with no success.

 

That seems to be pretty typical when one or more of the limit switches start getting flaky, sometimes it will shift on a key cycle and other times not.

You may check the vent hoses on the actuators first as it is common for them to crack and come off, then that happens the actuator will fill up with dirt and water and stop working.
If those are in good condition though then it's down to checking limit switch voltages to see which one(s) aren't working properly.

 

Did you try hitting the ADD while a friend engages and disengages the 4hi?

Some love taps won’t hurt.

if the doesn’t work, I’m sure others will chime in.

 

Haven’t tried this yet but I got the lights to turn off a few days ago and now they keep coming back on while driving normally in 2wd without touching the switch? I’m super confused with this whole thing now but it definitely seems electrical

 

I just got this issue fixed about a month ago. My problem was the ADD actuator. The gear had turned to much and got stuck, so when i would select 4wd it would flash just the 4wd light. I took it off and ran it with some jumper wires, then put it back on. It wasn't lined up right and blinked both 4wd and lo lights when in 2wd. I used the jumper wires to cycle it on them off while on the truck and that got the sensor lined back up.

If i was starting again i would try the jumper wires before removing the ADD to see if it would unstick with just the power. If not then pull the ADD and inspect the internals. Could be mucked up with crap.

Also, the vent lines were old and ripped off but luckily its been a while since i went through deep water and there wasn't anything inside. Watch youtube and you will see a few that were filled with mud and trashed. If youve already had to replace your transfer case actuator it might be the ADD now need replaced. What was wrong with the transfer case one? Filled with water and traashed?

 

Yeah my old transfer case one was ruined by water so it is possible that the front one also got ruined by the water I went through. What do you mean by using jumper wires on the front add while it’s on the truck?

 

I lack the knowledge to know entirely, so please correct me or tell me I’m full of shit.
From what I have researched the ADD and its associated components go through a checklist based on voltages, solenoids etc. And not though the ECM. (?)

I heard it’s a pain to diagnose, for example;
if you select 4hi and you turn off the car or the car turns off while it’s in the middle of the operation. When it “wakes up” it has no clue where in that process it previously at. So it just sits there and gives up showing some flashing lights.

Forcing the ADD to not be in the middle of said operation and to be in “A state” 4hi or 4low, “resets” all that so the voltages are back to A state of some kind it recognizes.

That’s what I understood it. I wanted to refrain from speaking about this as I’m not 100% familiar with this operation.

Go to 6min for the “checklist” and it’s specific operation.
source: https://m.youtube.com/watch?v=Lhx-RMhWyaM&pp=ygURY2FyIGNhcmUgbnV0IDR3ZCA=

 

The 4wd ECU alone is responsible for controlling the operation of the 4wd system, it uses 5 limit switches and 3 detection switches to determine the position of the Transfer Case and ADD. If it sees any one of them in an implausible state based on the rest it will halt all operations and flash the 4wd and/or L4 lights.
That's why it's possible if the key is turned off mid-shift for the actuators to stop in an implausible state, when this happens they have to be manually moved to a valid position.

Testing the switch voltages at the 4wd ECU is the easiest way to determine which one(s) are out of range, once that is determined then based on that info further testing/disassembly can be done to find the exact problem.

If you read the thread I linked above I have explained the system operation and sequence the best I can, we have found everything from simply contacts having a poor connection to broken/corroded wires and bad grounds.

Unfortunately Toyota didn't add on board diagnostics to the 4wd system on Tacoma's until 2016 so all prior models have to be tested manually but understanding the operation of the system goes a long way in making it easier to diagnose.

 

I plan on voltage testing the 4x4 ecu asap but I don’t have time for it at the moment. Tonight the lights came on so I restarted the truck and heard a thunk then I tried the 4x4 and it worked flawlessly. So then I thought maybe it had worked itself out but as I was driving home the lights came back on while accelerating. So I pulled over turned the truck off and on then tested the 4x4 switch and nothing but flashing lights again… could this mean it’s just a loose plug somewhere? I’ve already checked on the transfer case actuator but where else could there be a loose plug or bad ground?

 

I used power from a battery i either used a 6v power wheels battery or a jump pack, cant remember. A regular little 9v batter would work too though. jumper wires are the little wires with clips. I put a couple peices of stiff copper wire in the clips to use as probes. With the probes i ran the motor by touching the probes to the terminals on the ADD. Disconnect the plug and the bottom terminal would be terminal #1. Touch the positive power to terminal #1 and negative power to terminal #2 to move the fork into locked position. Reverse positive and negative to run the motor in Reverse which moves the fork out of locked position. Once you know its out of locked position reconnect the plug and start the truck with the 4wd switxh in 2wd position. If the lights are off hopefully it fixes the problem. It did for me.


If dirt and water got inside and it keeps running they will wear the position switch out. So the motor can still work but if those positions connections get dirty or worn out it wont send signals to the computer and you will still get the flashing lights. Then its time to pull the ADD off to inspect inside. Clean if dirty and replace if the position sensor has worn out.


This post tells how to do it and check if position sensor switch is sending the right signals to the computer better than i can.

 

Another update: I took off my transfer case actuator and tried re timing it, I was able to get it all back together so I went into the truck and all the lights were gone. I then tried to put it into 4wd and it worked flawlessly in and out of 4hi. Then about 30 seconds later I tried putting it into 4hi again and the 4wd and 4Lo light started blinking again like they used to. I’m assuming the issue is somewhere on my transfer case actuator but Im not sure if that’s just the timing or maybe a limit switch?