2004.5. have had dyna trac locking hubs for four years now. experienced something new today. first time i had to use 4wd this season. when i put truck into 4wd the dash light for 4wd came on. when i got to work, i noticed it was off but truck was still in 4wd. put truck back into 2wd then back into 4wd but the light would not come back on. on the way home tonight. the light lit up. almost home the light blinked or flickered a couple of times then went back out, but truck was still in 4wd. any ideas? just the light??

 

Check the codes for the 4x4 position switch, or something like that, I think it is P 0857.

My 4x4 light comes on when it is in 2H or N, but it goes off when it is in 4L or 4H, no codes though.

The light stayed on for about 10 miles once last year,after I shifted back to 2H, but then worked ok for the rest of the year. Now it is constantly on, no big deal, but it still kinda makes me wonder.

 

either a loose connector, chaffing wire or loose wire. Going to have to hand over hand your sensor switch to find where the problem is.

 

it is the switch on the transfer case. this is a common problem. they are not very expensive

 

AFAIK, the switch is integrated in the selector motor.

 

mine doesnt work either...truck goes into 4hi and 4lo but the light doesnt come on...

 

^ same here (lever shift) Tried holding the odometer button and turning the key on which is a gauges test and it still doesn't come on. bad cluster ? o well 4WD still works, I dont need a idiot light to remind me that i put it in 4WD.

 

I am having a similar problem with my 05'. Service 4wd light came on about a year ago. Transfer case cannot be shifted. I removed the gear motor that shifts the transfer case and tested with 12 volts. Works fine. The gear motor has an encoder on it as well with a separate 6 pin connector. The encoder probably tells the computer which gear range the transfer case is in. I have no way to test the encoder. Scanned with code reader, no codes. I was told that a special reader is needed to check for transmission codes? Would be interested in hearing other people's experiences.

 

Mine did that too luvdiesel. I replaced the shifter motor and the dash mounted module. Now it shifts, but the 4x4 light stays on in 2x4 and every once in a while, the Service 4x4 comes back on as well. No codes and dealer just scratches his head.

 

after doing what you stated here mine didnt come on either...maybe the light is burnt out...

 

Still have not resolved the problem with my 4wd. Since my last post I have replaced the shift motor/encoder, did not change anything. Recently took it to a mechanic who ordered a used transfer case control module. That did not fix the problem. He drove the truck to another mechanic that has the scan tool to read codes from the transfer case control module. The scanner reported something like: Switch???

Does anyone have experience with this?

 

Have you tried the switch on the dash?, it may have an internal short/ break causing your condition.

 

I opened up the switch and found nothing but a printed circuit board with resistors and LED's. I checked each resister against it's color code value and they all checked out good. All of the LED's light when the switch is plugged in. It goes against my better trouble shooting judgement to replace something that I can't find a problem with but I think I am to the point where I need to try a new switch.

 

I'm having an issue along these lines as well. My dummy light works but......when I put it in 4 hi sometimes the light just blinks and it won't engage. Other times it will shift into 4 hi but not 4lo...when that happens the light is solid in the 4hi position but flashing in the 4lo position and vice versa when it actually does go into 4lo.

Now for the weird part. If it does engage in 4wd it won't disengage until I shut the truck off and unplug the connections at the case, start the truck, plug the connections back in and only then will it unlock.

I've been looking for a solution for a while now but hit a dead end on every forum I've searched. I'm no good at diagnosing electrical issues therefore until I can find a definite cure I'm not just going to start throwing parts at it.

Another thing....I have no codes and the service 4wd light has never come on either.

 

same w/ me, i'm sure its the switch on the transfer case, but with the manual lever i know its engaging.. one day i need to just replace that switch...