4LO light still flashing 4HI or Low won’t engage

I would like to start with I am definitely not a mechanic.
My 4 hi & 4 lo lights were flashing and 4x4 would not engage at all. Worked great all last winter going in and out 4HI and 4LO . Mechanic said new 4x4 actuator was needed. He replaced that still would not engage and same issue persisted. Said it was the front differential then. We replaced that and now both 4HI and 4LO lights are solid and neither will engage. Checked the fuses and replaced the 4X4 one in the Kick panel within the cab. Now 4Lo light ONLY flashes with no sounds of it trying to engage just in 2WD. I’m at a loss my mechanic is now saying maybe it’s an Evap issue . Anyone else had the same issue ? I love my truck it’s perfect for my job but I live in a heavy snow town and absolutely have to have reliable 4x4 any insight on this issue ? I don’t see any reason it would not work still with a new actuator and front diff

 

Sounds like your mechanic just fucked you out of a couple grand, to his benefit. That’s unfortunate. It may just be the 4WD ECU is shot, honestly. Did the mechanic bother to perform any diagnostics? Sounds like they just threw parts at the problem.

 

About 800$ including labor now …. Not horrible but still sucks but has been dependable before this and although I’m not with him when he diagnoses I would in the past trust what he does …. But feel like the problem would be diagnosed by now nice guy getting fucked probably you’re right haha . With more research I’ve had some friends tell me it may need a wheel speed sensor

 

Are you seeing any other symptoms indicative of WSS? Speedo reading off, ABS codes, anything like that? I’m spitballing because I can never remember which models gauge speed off trans versus WSS or whatever. I always need to look it up, and others typically correct me when I’m wrong.

 

Tire pressure light on , 4LO flashing & MAINTENANCE REQUIRED light no codes thrown gauge speed works no ABS light

 

Does your truck have a cold air intake? Have you fiddled with or cleaned the MAF lately?

 

Maintenance light takes 30 seconds to reset.

TPMS light for tire pressure is an easy enough fix - if solid, you’ve got a low tire, if flashing, you’ve got a bad/missing sensor, both can be remediated without buying new sensors/hardware but it’s not causing this problem.

EVAP issue is emissions system; what logical conclusion would draw your mechanic to thinking something in an emissions system would stop 4WD from engaging? That sounds like a load of BS with no logical grounding but I’m pre-coffee right now so maybe I’m just slow.

I openly admit: I’m not the guy to talk to about 4WD on these trucks or any other. There are better minds than me on here for that. But I also find it interesting the behavior you’re witnessing changed after swapping fuses.

I hate to play “parts cannon” like the mechanic is but have you considered the 4WD ECU in the passenger kick panel is bad? It’s a plug-and-play test/solution that doesn’t require a mechanic. It falls under “parts cannon” because I personally don’t know how to test it, but replacing it has been a fix for a couple of other folks who were seeing truly bizarre illogical ass shit from their 1st gen 4WD. I can’t recall whether the FSM includes debugging info for 4WD or its ECU, but links to the FSM are in the top of the sticky mega thread (“So you just bought a Tundra eh?”)

 

My next step is replacing the ECU , I really appreciate the time and advice I have gotten from this thread. .scrambling to get this fixed before it snows and appreciate any help I can get

 

No cold air intake I believe and no cleaning or fiddling with MAF

 

Did you bother to check if the front driveshaft wasn’t spinning when placed into 4wd HI? Sounds like your tech didn’t if he went ahead and replaced the front actuator.

I would go ahead and put a piece of masking tape on your shaft and see if it spins when you attempt to put it in 4wd HI before you go the ECU route. Also drive back & forth in forward and reverse to see if that engages it.

 

Ask the mechanic if he disassembled the transfer-case to replace the actuator, or took the triangle cover off and pulled the little gear. I’m doubting he pulled the case, as that is a huge project, so, I’m guessing he used the short cut method, and maybe the gears in the actuator are not clocked properly.

It shouldn’t be hurting anything. The truck is probably picking up its in the wrong position, and not functioning.

I haven’t done this on mine, as my actuator was replaced by the dealer right before I bought my truck.

Either that, or it’s none OEM parts, and could be faulty.

You could have someone turn the key to “on” crawl under the truck and have them press the 4x4 button, you should be able to hear the motor run and the gears shift in the case if it’s running properly.

Edit: Also, this is a very expensive repair at Toyota like $3,000+

 

4spd goes off trans, 5spd goes off wss.

 

Did your mechanic open up your transfer case to replace that actuator?

I disassembled and serviced both my front diff, and transfer case actuators. The front diff is fairly simple. The transfer case though is another story. This is my understanding, you can do it two ways. split the transfer case and take the whole actuator out (with the shift rod) as one and replace it.
Or do like I did and remove the small gear that locks it in place and remove just the actuator. Problem is after you clean up the traces and reassemble it you need to "clock" it perfectly or the truck may be in 2H, and the actuator in 4Lo/4Hi. I managed to get 4Hi to work, but not 4Lo.
I sat and stared at that mechanism for a long time trying to decipher what I was doing wrong.... after 3-4 attempts I settled for 4Hi only. For now anyway.

 

So the front is pretty easy? I pulled the add tube to the clamshell and plan on using my ADD tube on the donor diff. I’m hoping I can just add some silicone gasket and slap mine on

 

Yes, not bad at all. Thing is you can actuate it (just hanging there) and tell if its engaging or disengaging. If you parked in 2H, then set it disengaged and slap it on, and vise-versa.

They do get crusty in there, green is bad

 

I didn’t even want to go that far, just swap the entire tube, my thing, I know for a fact mine works without issue, I don’t know about the donor diff.