P1782 Truck Thinks It's In 4LO, but it's in 4HI

[derekdevasia]

Hi folks,

I've read threads of people having the P1782 issue, but I think my issue is a little different. I took a labor day trip and we hit some off road trails, went through some mud, rocks, ect. Nothing out of the usual for this truck. I ran all of this while in 4LO. After the trail turned to just gravel, I put it in Neutral, selected 4HI, and heard the gears engage. The light for 4LO never went off, so I put it in drive after about a minute or two just to get things rolling. (Sometimes this works) Well, it started beeping at me. I went back into N and shifted back into 4LO, and the beeping stopped, but then when going back to 4HI, nothing.

I unplugged the negative cable and let the truck sit for 30 minutes twice, thinking maybe a hard reset would fix it. I then also drove for a little thinking maybe it just needs a second. I also tried to lock the center diff, and the light stayed on solid after a few seconds indicating it was locked, but it does NOT feel like it was locked. I did this numerous times, unlocked, locked, and switched back and forth from 4LO to 4HI about 50 times to try to see if it would free up. I don't hear anything other than an electronic beeping/whine when trying to go into 4HI.

Here's the main issue, the truck THINKS it's in 4lo. It's really in 4hi. How do I know this? I drove home 4 hours in "4lo" while cruising 65mph at 2500 rpm. That just wouldn't be possible in 4lo. It feels like it normally does in 4hi. What the truck has done, is that it looks like it has shut out overdrive because it thinks its in 4lo, as usually at 65mph my rpm's would be around 1900.

Here are my three questions:

1. Can I trick my truck into thinking that it's in 4HI (because it is) so that I can get my overdrive back, the CEL gone, and I can drive my truck like normal until I can decide what I want to do.

2. Do you believe this is the actuator in my truck? I routinely exercise it ever since I've had it (10 years, 160k) Or do you think that maybe this could be a transfer case position switch? I've heard those go bad in 3rd gen but couldn't find any such issues in the 4th gens.

3. If it is the actuator, and I can get the truck to think it's in 4hi again and behave like normal. I'll be attempting the FJ cruiser transfer case swap with the twin sticks so I can get rid of the electronic actuator for good when I have some spare time in the next month or two. For those who have done this, I've read A-Ha's thread, did you all get a new Tacoma/FJ front diff? The only thing holding me back from doing this is the trimming of the oil pan with the new diff.

 

[Trent]

There are 6 switches in the actuator. I can send you information about which switches should be closed or opened in any given mode. Let me know.

 

[Trent]

I think you should start with unplugging the 12 wire connector, clean the contacts good, reconnect, and then visually inspect for other wiring damage. Inspect the a actuator itself for physical damage. Interesting that the problem showed up after you were on some rough terrain.

 

[AuSeeker]

There are 6 switches in the actuator. I can send you information about which switches should be closed or opened in any given mode. Let me know.

It would be useful info for many here if you just posted the information on the forum.

 

[Trent]

It would be useful info for many here if you just posted the information on the forum.

I will try to upload an image of my spreadsheet...

 

[derekdevasia]

I think you should start with unplugging the 12 wire connector, clean the contacts good, reconnect, and then visually inspect for other wiring damage. Inspect the a actuator itself for physical damage. Interesting that the problem showed up after you were on some rough terrain.

The actuator and wiring didn't have any damage, as that was one thing I did check as i slammed down on some rocks. The RCI skids did a good job there. I didn't unplug the 12 wire connector, but I will give that a try, and thank you for the suggestion and for the diagram!

It might be a day or two before I can get under there, we're getting hit by Dorian currently into tomorrow.

 

[derekdevasia]

Well I haven't had much time to work on the 4runner with clean up efforts from Hurricane Dorian and work. For anyone else that ever experiences this issue, I've discovered that disconnecting the two harnesses for the 4wd computer located under the glovebox, will let your truck drive using overdrive. Not only that, it will resolve your check engine light, as well as the 4lo light blinking. You will have the trac and stability control lights on however. Thankfully now at least I can drive on the highway without higher RPM's and truck drives fine. Might be a little bit before I troubleshoot further.

I thought perhaps it was my 4wd computer, and tried a 4wd computer out of a friends 4runner that has the identical part number. That did not work, and the beeping was still there and the truck still thought it was in 4lo. Worth a shot.

 

[sozon]

Well I haven't had much time to work on the 4runner with clean up efforts from Hurricane Dorian and work. For anyone else that ever experiences this issue, I've discovered that disconnecting the two harnesses for the 4wd computer located under the glovebox, will let your truck drive using overdrive. Not only that, it will resolve your check engine light, as well as the 4lo light blinking. You will have the trac and stability control lights on however. Thankfully now at least I can drive on the highway without higher RPM's and truck drives fine. Might be a little bit before I troubleshoot further.

I thought perhaps it was my 4wd computer, and tried a 4wd computer out of a friends 4runner that has the identical part number. That did not work, and the beeping was still there and the truck still thought it was in 4lo. Worth a shot.

I'm having the same exact issue and symptoms after fording water, did you end solving this issue? I have tried disconnecting everything, the battery, the ECU under the glove box, the actuator plug, you name it. no luck.

If anybody can chime in and solve this, I'll be forever grateful.

 

[Jack.T4R]

Well I haven't had much time to work on the 4runner with clean up efforts from Hurricane Dorian and work. For anyone else that ever experiences this issue, I've discovered that disconnecting the two harnesses for the 4wd computer located under the glovebox, will let your truck drive using overdrive. Not only that, it will resolve your check engine light, as well as the 4lo light blinking. You will have the trac and stability control lights on however. Thankfully now at least I can drive on the highway without higher RPM's and truck drives fine. Might be a little bit before I troubleshoot further.

I thought perhaps it was my 4wd computer, and tried a 4wd computer out of a friends 4runner that has the identical part number. That did not work, and the beeping was still there and the truck still thought it was in 4lo. Worth a shot.

Any word on fixing it? I've encountered the exact same issue just recently. If you have any advice at all, I'd love to hear it. As for the 4WD harnesses, I'll give that a shot to get my overdrive back, but I'm curious if you ever figured out the root cause.