SOLVED! 4WD flashing.

2004 Tundra SR5 4.7L automatic with 4WD 233k miles. The 4WD light flashes when I try to engage 4-HI. The drive shaft to the front differential engages and I can hear and feel the front differential actuator activating when the button is pressed but the light flashes. I'm assuming the both actuators are working. Earlier in the day, 4WD (an 4WD Low once Hi was engaged) started to work. I nonetheless decided to pop the front accuator connector off to insoect for corrosion. It was fine so I reconnected and I can't get in to 4WD Hi but as mentioned, the actuator seems to respond. So my qyestion is...if both actuators are working Ok, what else could cause the flashing 4WD light? Thanks.

 

You'll need to get the truck up on four jack stands so you can verify the front diff actuator is actually engaging. It could be turning but not enough.

It's good that you already verified the transfer case actuator works by confirming the front driveshaft is spinning.

I'm willing to bet the front diff actuator is failing.

 

Nickrick...you could be correct. Originally the front actuator wasnt working at all. I got it moving but maybe not enough as you've stated. Thanks.

 

I will assume you've checked fluids in the transfer case and front diif.

Some have found that simply engaging (in loose conditions) 4HI and throwing in forward and reverse a few times will shake things loose enough to get a good engagement. Toyota recommends driving at least 10 miles per month in 4HI to keep the 4WD system healthy. If you and/or a previous owner haven't been doing that, I'm going to assume things are just jammed up, again assuming fluid is ample and semi-fresh.

A few folks have found the 4WD ECU to be bad when squirrely things are happening. I don't know how to test for that. Apparently neither does the stealership, because at least one guy on here ended up forking out the nose with no results only to replace the 4WD ECU and *poof* things started working. Wish I could find that thread ...

 

Fixing this system can be tricky. Let us know how it goes!

 

Some background info...I changed all the fluids recetly. I used Valvoline 75w90 compatible with the LSD rear differential in the transfer case and front differential. Old fluids look ok. The Tundra get on the beach the warmer months. I engage the 4WD over the winter but probably should do it more often. The 4WD has been finicky since last year. As of last year, it would sometimes work fine and others times I get the flashing 4WD hi light. However, once it started working last year, it was fine the remainder of the season. Seems like a similar situation this year. It's been finicky. It started engagiing earlier in the day yesterday but not at all after I cleaned the contacts. Should have left good enough alone I suppose.

 

Interesting. This has nothing to do with it, but was the rear oil synthetic or standard? I tried running Mobil1 synthetic in my LSD rear and the chatter I was getting out of the rear with it was obnoxious. Others using full syn saw the same.

I'd be tempted to hit a JY to try and get a 4WD ECU, but that would be throwing parts at it. I'm not sure how to diagnose ... that's been an ongoing issue. Some steps you could give a go at are here. Best I could come up with.

Links to the field service manuals can be found in the 4th or 5th paragraph here.

 

Im using the non-synthetic valvoline 75w90. Comes in a 1 quart white bottle. Put it in the rear differential where I got the Tundra 4 years ago and no issues. Now I replaced again and also used it in the transfer case anf front differential.

 

Oil is not likely the issue

 

I'd also recommend doing the 4hi & 4lo actuation on jackstands. Really help troubleshooting if your brakes arent dragging.

 

Totally not, but still worth asking about. If volume of oil was low in the TC, I could see stupid shit happening. And curiosity got the better of me asking about what he dropped in that rear LSD after my fun times...

 

UPDATE: Things got a bit worst. Now if I engage the 4WD-Hi switch, I continue to get the flashing light but if I push the switch back to 2WD, the flashing light continues flashing. Previously, the flashing would stop in the 2WD switch position. If I turn the steering wheel to the full right and move a few feet in reverse, it sometimes stops flashing. That's hit or miss. If I engaged 2WD, and let the vehicle sit for a while (8+ hours), the flashing light usually doesn't resume when I restart the vehicle. When the 4WD-Hi switch is engaged, the front driveshaft to the front differential does not turn. In the 2wd switch position, the front driveshaft can be turned. That seems to be telling me the transfer case actuator is working. As soon as I can, I am going to tap the front actuator a few times with a hammer to see if that at least stops the flashing when the switch is in the 2WD position. I am now certain that I will need to remove the front actuator & open it up to see what it looks like inside. I suspect the actuator isn't working properly, even though I can hear and feel some internal movement when the 4WD-Hi switch is engaged. While the front actuator isn't completely frozen, the inside of the actuator must be corroded enough to be giving me these issues. I'll keep posting my progress and hopefully I'll be able to provide a solution in case someone else runs in to a similar situation. I hate posts like these that never provide the fix.

 

Thinking out loud here... it sounds like something doesn't know what position it is in. You mentioned that everything seems to be moving. Wondering if either the tcase or front diff isn't giving the signal that it is where it should be. Dirty contact maybe?

 

Yup...this

https://www.tundras.com/threads/4wd-issues.119382/#post-3081795

 

Had some spare time today so I raised the front wheel of the Tundra on stands. With 4WD HI switch in the 2WD position, both wheels spun freely and the front drive shaft would spin if I tried to turn in manually. When I pushed the switch to the 4WD position, the front drive shaft was locked and would not spin if I tried to turn it. However, both front wheels spun. Therefore 4DW is not engaging at the front differential. I believe it's safe to say it is the front actuator is not working. One other point to make is regardless of which position the switch is in (2WD or 4WD-HI), I still get a flashing light. Aside from the front actuator, could the fault be with any 4WD ECU or maybe the 4WD HI sensor switch that's mount on the transfer case actuator? All the wires and connectors seem fine. Thanks!

 

The front actuator my be "hung" in between positions. Some people have success rocking back and forth in D, then R. Others have found that a couple of strategically placed smacks with a hammer can help to loosen the fork. The front actuator is a bitch to remove! (That reminds me, he said parenthetically, I need to remember to drive around in 4wd today).

 

Some progress, but not perfect. I was able to take a better look at the front actuator harness and found the grey wire on the plug that snaps into the actuator was broken. I took the entire harness off to do the repair. It's only about 10 inches long so removal was easy. Further inspection revealed that every wire on the harness was previously spliced/repaired. I repaired the grey wire and checked continuity on both ends of the harness. All checked out OK.

The Good: I reconnected the harness and now I have no flashing light when I push the switch to engage 4WD-Hi. 4WD-Hi is working fine. All four wheels turn when the 4WD-Hi switched is engaged. When I de-active the switch, the Tundra returns to 2WD as it should.

The Bad: When I de-activate the 4WD switch to return to 2WD, it returns to 2WD but I get the green flashing light. I suppose it really doesn't matter since aside from the annoying flashing, the tundra is in 2WD and all else seems OK.

More Bad: While I am able to get into 4WD-Hi, I was only able to get a response only once when I tried to go to 4WD-Lo. I went to low while in 4WD-Hi, green light solid (not flashing), and after I put the transmission in N and Tundra wasn't moving, I pressed for 4WD lo, the amber light lit up and I had low. When I tried to return to 4WD Hi, the Tundra responded weird. I hear a strange & somewhat loud noise. I haven't gotten 4WD-Lo to respond anymore. I took a break and will try it again shortly.

What's next? I'm trying to find the part number for the harness. I don't trust the old one so I will replace it with a new one. I know the part is available and list price is around $67. The VIN is 5TBDT44164S444191. (2004 SR5 DC Tundra 4.7L 4 speed automatic). If any can look up the part number, please include it in a reply. I am hopeful the remaining issues with the 4WD are related to the old harness. While I did the repair as best I could, it's still in questionable condition.

 

Progress Report---I doubt anyone is interested, but in the event someone runs in to same issues as I have, I am going to keep posting updates and hopefully the final fix. I believ I am getting there.
I had to replace the section of wire harness that plugs into the front differential actuator. The found the part I needed (Toyota OEM part #82127-0C010 cost me $38 at the dealer, but purchased from their online site).
To my surprise, the actuator vent tube came with the harness. I thought for sure the actuator was corroded so I pulled the plastic cover off. However it was really clean inside. No corrosion, though the "yellowish" grease was a bit dry in spots. I put a light coat of dielectric grease and reassembled the actuator. I then found the wire on one of the transfer case indicator switches was also broken (cut through, the wire wasn't making contact with the push on connector). I believe that is why the 4HI light flashes when the switch is in the 2WD position (it's a solid green when the 4HI is engaged). In testing how things are working, I am able to go in and out of 4HI to 2WD. Going in to 4LO from neutral once I'm in 4HI isn't working. The amber colored 4LO light flashes and then shuts off and the 4HI green light illuminates without flashing.
The remaining issue with 4LO could be all due to the one wire on the transfer indicator that's broken, at least that's what I am hoping. So now I'll search for the correct push on connector for the transfer switch. If anyone out there might know, of the two transfer switches located by the transfer case actuator, the one with the damaged wire is the one closer to the rear of the Tundra. The adjacent transfer switch, which is closer to the front of vehicle, seems to be OK. I have no idea how that wire got damaged. The electric harness that I had to replace was repaired by someone prior to my owning this Tundra. It was a shoddy repair. Each wire was twisted together, no crimp connectors or solder, and taped up. The bare twisted wires were corroded.

 

Heck yea, keep the updates rollin. It's 10x more help than a buncha folks sitting around playing 20 questions.

 

4LO happens exclusively at the transfer case (once you're in 4HI and Neutral, of course). There are a couple switches that monitor the position of the actuator rod. Another place to check for mangled wires

 

If I am understanding you correctly, the front connector is 4WD and rear is L4.
If you're wanting connector part #'s, this is what 2004 EWD has...

D 3 Detection SW (Transfer 4WD Position)....90980−11250
D 4 Detection SW (Transfer L4 Position)....90980−11025

 

Thank you BubbaW! I ordered the L4 connector 90980-11025.I should have it tomorrow.

 

Update as of 6-13-2023: I replaced the broken wire connector that attaches to the L4 position switch. I also checked the L4 switch with an ohm meter to ensure it was working. It is open when the plunger is not pushed it and it is closed when it's pushed it. So it works. I did the same with the 4WD position sensor and it's fine as well. I was optimistic that this repair would be the final fix but it's not. I still get into 4WD Hi when I press the button but no flashing green light. However, when I disengage 4WD Hi, I get a continuous flashing green but the vehicle returned to 2WD. If I push the 4Lo button while I am in neutral with 4WD engaged, I get a flashing amber 4Lo light and 4Lo is not engaging. After a few seconds, the amber flash stops and the vehicle goes back to 4WD Hi with a solid green light.
Not sure what else to do. I am getting discouraged as I was certain the repair of the L4 wiring would of solved the problem. In fact, it did nothing. The same issue exists before I repaired the L4 wire connector. I need a schematic to trace both wires on the L4 connector to wherever they go. I'm assuming either wire or both is damaged somewhere else down the line. It as though I didn't do the repair. For the past several days the L4 connector was detached and both connector wires weren't connected to anything. The ends were separated and each end protected with a bit of electrical tape. The vehicle is doing the exact same even though the L4 connector was repaired. I'm leaning in the direction of a wiring issue. However, I also noted the rear actuator plastic housing is cracked around each of the housing bolts. However, the front axle is locked when I push in the 4WD Hi button and spins freely when I return to the 2WD position. For this reason I am assuming the rear actuator is OK. The other possibility is the reassembly of the black plastic housing of the front actuator was out of time, but I had the geared wheel rotated as far as it would go counterclockwise when I installed the housing back on. There is a possibility that something is wrong there. I'll continue on this repair but I might take a break for a few days.Very disappointed today's repair didn't solve the mystery. Murphy's Law.

 

The attached is the pages from the 2004 EWD regarding 4WD (DC) circuit schematic.

If you haven't already, I'd suggest downloading the whole 2004 EWD from link below. You then can possibly find all the junction points from point A to Z.

I have also attached 2 Toyota Quick Training Guides I downloaded from TIS that their technicians uses.

Ultimate TUNDRA Wiring Diagrams Collection | Toyota Tundra Forum (tundras.com)

 

I'm still skeptical of the 4WD ECU. I know I always say that, but it seems like every time the rabbithole gets this deep and the same response is being, it's 50/50 the 4WD ECU has gone bad.

You'll see it tucked away in the passenger kickpanel area or under-dash in Bubba's diagram a few replies up.

 

I can't count out the possibility that the 4WD ECU is bad. However, I didnt like that the transfer case actuator black plastic housing is cracked at each bolt hole. I suppose its possible water got in there. I go on the beach often and always hose the entire underside each time. I know the frame is prone to rot so I rinse it off well. What I dont know is whether 4lo is involved with the 4lo function or if that is controlled by the front actuator and ECU. Theres the L4 switch so the TC actuator plays some role. 4WD works fine, just 4lo is a problem. I downloaded the 2004 FSM (thanks for the link)! Im looking at page 627 or so, which details the schematic. I want to confirm each wire of the L4 connector has continuity from the connector end to the opposite end. If there's continuity, I may open the TC actuator. Being cracked can't be a good thing. Besides that, as I mentuoned earlier, I may need to somehow confirm the ADD plastic cover is in tune with the gearing. Sorry if my replies are too long-winded. Just a lot being considered and I still cant say the ECU is good. Wish it were a cheapo part just to get that possibility out of the way. Thanks for all the help.

 

Hi Everyone, I am new to this forum but have lived with my 2005 Limited DC since it was new.. Now have 128K on it and am experiencing very similar issues as seachunk2.. RIght now I drained the front Differential, rebuilt the little stepper motor on the Front axle ADD, because one of the field magnets had come loose and motor would not turn.. The issue with the flashing 4wh HI and LOW lites is all most identical to seachunk2 's situation, even as to both hi and low lights continously flashing regarddles of button engagement and ceasing after sitting for several days. They will stay off untill I press the 4 wh hi button, then scenario starts all over My front drive shaft will not turn, but have not jacked up wheels to check if the front axle is engaged. I reinstalled the base of the ADD without the cap and gear and slid the collar over to the side closest to the axle carrier housing( pax side) I assume that my transfer case has engaged the 4 wheel hi, since others in this forum have said that if you can not turn the front drive shaft then that indicates it is in 4 wh hi as far as the transfer case is concerned.
SOoo, here is where I am at. When I probe the 6 pin plug that goes into the Front ADD, I can not get any pin showing power.. I believe that power oscillates between pin 2 and pin 6 to cause the motor to run in both directions.. I have tested the ADD motor after I restored it and it runs strong when I had it off the axle. I will try to remove the harness that feeds that ADD plug and check it for continuity.. I will also plan on putting my front tires up in the air and check if the Axle is engaged.
Now my other problem is that I did not note the position of the gear in the ADD after I removes it and dissasembled it, so I have no way of making sure that the contacts will be aligned properly when I get power restored to the ADD harness plug. I have the service manual and it does not offer any help in any of these issues except the description of the pins in the ADD harness. Any comments , suggestions etc, will be greatly appreciated.. a detailed wiring diagram would help, especially to show where the power to the front ADD comes from would also very helpful. I have checked the fuse in the cabin for 4 wh drive. Not sure if there are any relays the system Thank You, John R in Auburn, NY

 

Stupid question, but you said 'no power', did you check the 4WD fuse in the dash? Not sure it would cause this, but my '06 has one, and it's the first thing I'd be checking. Have you been engaging the 4WD at least 10 miles per month per the Owner's manual recommendation? Have you tried the following steps, just for sanity check?

 

HI shifty, Yes I did check that cabin fuse and it was good. I have not found any relays under the hood that are labled 4wh drive.. As far as using the 4 wh drive, I have had this flashing issue and no front wheel engagement since last summer. To answer specifically your question, I do not regularly practice the engagement procedure, since I have had this truck for 18 years and have not had any problems with getting 4 wh drive when I needed it.. The only thing that I have experienced for the past 7 years would be a flashing green light on the 4 wh hi button when I tried to engage the 4 wh hi after the truck had been running for some time. Never happened in the winter, just during the summer months, say when I would attempt to take our boat to the local water ramp. If I drove to the ramp in 2wh, I would always get the flashing light and no engagement.. If I engaged it just after starting four wheel engagement would be normal. If I disengaged it, it would not re-engage till the truck was off for several hours.. I was told that the heat from the rear cat was causing the actuator not to operate.. I lived with that issue because I used the 4wh drive very little in the summer, and it worked fine in the winter.. I have not done any testing regarding the transfer case and its actuator.. I will take a look at " the following steps".. thanks for you rapid response.. john R Shalom

 

Got it. On the actuator topic, if memory serves me right, the video in the reply I linked to covers what to check in the actuator itself, making sure the contacts aren't corroded. You can ignore all the fancy wiring and crap he's hooking up to the actuator. He goes into great detail on the actuator itself, how it works, and diagnosing it.

There's also a breather tube on the actuator that, in most cases, eventually becomes brittle, cracks, and breaks which allows elements inside, dirt, water, salt, humidity. While I had the actuator cap off to check the contacts with a fine tooth comb, I'd also be verifying the state of that tube.

The fact it has issues in summer, when humidity is typically high up and down our coast, I think it's an important symptom.