4WD light flashing intermittently, doesn't go into 4HI or 4LO

Hello everyone, this is my first post on TacomaWorld and I just want to thank you all in advance for your time and help. I just purchased a 2008 Tacoma, V6 4.0L, 4WD and 6-speed manual and I'm having some issues with the 4WD. It had been sitting for awhile, but previous owner stated that he drove in 4Hi at least once per month. Okay, here are my experiences with it:

At first the 4LO light would blink as soon as the ignition key was in the "ON" position (Engine Off). I would hear two clicks from what I presumed was the 4WD ECU behind the glove compartment, immediately followed by the 4LO light flashing. This would remain on after starting the truck and the entire time I was driving around. Only when I stopped, turned the truck off, and then turned the key back to ON position would it sometimes not re-occur. Sometimes I could drive for two minutes and it wouldn't flash when restarting the truck, other times I would drive for 20 - 30 minutes and it may or may not flash again when restarting.

When the 4LO light wasn't flashing, I would attempt to switch into 4HI. Sometimes it would switch in without problem, and I would hear what I presumed to be the transfer case actuator and front diff ADD actuator clicking. The truck was definitely in 4HI, and I could successfully place it into 4LO as well. Once it was in, I would not have any problem going from 2H to 4H and back again, or from 4H to 4L and back again.

However, sometimes when the 4LO light was not blinking, I would attempt to switch into 4H and the green 4WD dashboard light would simply blink. I could try going forward, reverse, turning the steering wheel, switching from 2H to 4H and back again while driving 20 - 30 mph, but nothing would be successful. After reading on here about the front ADD problems I decided that was the most likely culprit. I pulled the ADD and noticed that the connections were good and there was no corrosion. After cleaning up some hardened lithium grease and soldering the proper connections to prevent problems in the future, I put everything back together and topped up the gear oil. That evening the 4WD light would only blink, and the truck would not go into 4HI even after driving around for awhile and ensuring everything was warmed up. However, the next morning with a completely cold engine I attempted to place into 4HI prior to starting, and it immediately locked into 4HI. It was cold that morning, about 28 degrees Fahrenheit, and this was accomplished prior to starting the engine.

Later that same day the 4LO light was flashing when I turned the key to the ON position. I drove about 10 - 15 miles and stopped to get gas. When restarting, the 4LO light was off, and when I flipped the switch to 4HI the truck immediately went into 4HI. Again, I was able to switch from 2H to 4H multiple times without failure.

However, this is not consistent, and some days the 4LO light still flashes when first turning the key to the ON position. And if it doesn't, I cannot consistently get the truck into 4HI. Some days I can, and other days it just will not go. It does not seem to depend on weather, temperature, whether the truck has been warmed up or not, or if I attempt to switch into 4HI with the engine running or not. When the truck will not go into 4HI, I do not hear any clicking from either the transfer case or front differential ADD.

I visually inspected the ECU behind the glove box, and all of the connections appear clean and without corrosion or loose wiring. I have tried tapping both the transfer case actuator and front diff actuator in case something was stuck. I visually inspecting the wiring for both, and I do not see anything loose, broken, or corroded.

Any ideas on what I should check next? Thank you again for your help!!

 

I have similar issues. Sometimes the 4HI light will flash even though I haven't turned the knob. If I cycle 4HI and back again it stops. I too have also heard the clicking when turning the ignition on from the 4WD ECU. When that happens I see both the 4HI and 4LO lights, flash once, but they have never stayed on. If you find out what is going on I would love to know myself

 

You're not alone. Many things to do, luckily for me it was something like a $15 fix

https://www.tacomaworld.com/threads/how-to-trouble-shoot-4x4-actuator.263525/

 

I ended up taking mine to the dealer for them to run the diagnostics on it. According to the dealer, there was a leak in the fuel or emission system somewhere that caused a check engine code to fire, and this in turn disabled the cruise control and 4WD as a safety measure. I am not completely sold on this, as the check engine light was not on when I posted this issue (the maintenance required light was, but not the check engine light). Anyways, the dealer assured me that the 4WD functioned normally once the code was "resolved."

I will have to wait 3 - 4 weeks to find out, as the frame failed inspection and is covered under the recall/warranty. So I'm getting a new frame, plus whatever issue caused the check engine code will also be fixed. I'll update once I get my truck back in early May.