Yellow 4 wd service light came on

[Turbo Terry]

Yesterday while running some Christmas errands I heard a bonk like something tippped over then a bong and then the dash light came on . In Alaska we are constantly in and out of 4 wheel drive. Bare roads and slick side streets etc. Transfer case fluid was just changed to Amsoil atf +4 in November. The bonk sound was the transfer case going in or out of 4w drive No grinding. At next stop I shut the truck off and did a restart and light went out.No lights since all seems normal. Thoughts please

 

[Diesel85]

That's not good. I wonder if your transfer case motor is going bad?

Only other thing that I can think of is that the gears were still under a little bit of load and it malfunctioned that time when disengaging.

There has been times on my work 2020 that I've heard that noise. Maybe once or twice a year, but that is after using 4wd a few hundred times. I attribute it to the gears being under a slight amount of load and the system "yanking" on the setup. Never got the 4wd error message/light before though.

Man, I wish I had the AUTO mode like I do on my 1500. Hope the 2025's come out with it. It is so convenient when I don't need full/true 4x4.

 

[Turbo Terry]

Yes my wife’s Lexus is a no brainer just drive

 

[Grumpy8811]

Yesterday while running some Christmas errands I heard a bonk like something tippped over then a bong and then the dash light came on . In Alaska we are constantly in and out of 4 wheel drive. Bare roads and slick side streets etc. Transfer case fluid was just changed to Amsoil atf +4 in November. The bonk sound was the transfer case going in or out of 4w drive No grinding. At next stop I shut the truck off and did a restart and light went out.No lights since all seems normal. Thoughts please

didn't say if you have manual transfer case or the electric version or if it is the Service 4wd or Shift in Progress warning lite but generally problems with the connection on
the front axle disconnect solenoid can show up as a Service 4wd light.. it could have been wet or had a crappy connection for a short period of time and it reset itself when you turned off the ignition..

I used to have issues with the 4wd Shift In progress lite on my truck in damp conditions, never did exactly figure out what it was but it stopped doing it some time back..

 

[Turbo Terry]

Sorry electric on the dash. Drove it today in and out of 4 hi etc no issues. Transfer cases can be finicky beasts

 

[Grumpy8811]

Sorry electric on the dash. Drove it today in and out of 4 hi etc no issues. Transfer cases can be finicky beasts

4wd system itself is simple... there isn't much in a transfer case but a chain, a pump and a planetary gear.. front axle disconnect is simple too..
but the stuff is subject to poor connections and wiring snafus and will illuminate that service stuff .

 

[wyosteve]

Check the front axle disconnect actuator. A fairly common issue either going bad or having electrical connector problems due to moisture, or a bad connection.

 

[Turbo Terry]

Good info thanks. Drove. truck yesterday no yellow lights. I’m on a wait and see approach . I think Max care covers it and I have three years and 30 k miles left if it’s the 4wd actuator. Wait and see