Service 4wd Light

[Blue_Z71]

I was doing some wheeling today for about 4 hours, and as I was heading back towards the road, my 4wd quit working. Then got stuck in 4low after I did some tinkering. I FINALLY got it back to 2high, and made it home. I was going to go back out and do some camping, but now when I started it again, it's somehow back in 4low? And now the selector switch doesn't light up. I visually inspected the solders on it, I wiggled some connectors on the transfer case and front diff, and even changed the fuses, but still nothing. After all this, NOW it won't shift from 2nd gear!!!! I can manually shift from 1st to 2nd in tow haul mode, but in Drive it stays in 1st. When shifted into 3rd, it revs to the moon..... I'm so aggravated....any ideas wether it will be the 4wd switch, the TCCM, or the actuator/sensor? I'd get it scanned, but that's a $50 tow fee that I'd like to avoid.

[bigredmariner]

It sounds like the encoder motor sensor has failed. When it showed in 4LO you probably were only in 2HI but the shift tables were set for 4LO due to mis-information from the encoder motor sensor. It's a fairly easy fix and costs less than $100.

 

mine did the same thing a few months ago, motor lugged down and almost died when I came to a stop. I had to manually shift to low 1 for it to recover.

[Blue_Z71]

Hahahaha I woke up this morning to see if anything had changed, and sure enough, no service 4wd light, the 4wd selector was illuminated, and it switched from 4low to 2hi with ease. Now what??

[gmtech4]

get it scanned and report back with the code

[[email protected]]

It's gonna do it again eventually, that "encoder" cracking overtime and getting water in it is as common on these truck as having to change a battery. Just do a search, you'll find many topics on it.

[bigredmariner]

That's the same thing mine was doing the last time I had the problem. When I changed out the encoder sensor I took it apart and found that it had oil and gunk on the contacts, from what I have read it was causing an error between commanded and actual position because the sensor wasn't telling the TCCM the same position that the switch was calling for. I cleaned up the old one that I took out and will try to install it again if I have another problem.

Hahahaha I woke up this morning to see if anything had changed, and sure enough, no service 4wd light, the 4wd selector was illuminated, and it switched from 4low to 2hi with ease. Now what??

[Blue_Z71]

Thanks for the help guys. I'll hopefully get it scanned tomorrow and see what they say.

[Blue_Z71]

Got it checked....this is the sticky note he gave me.

 

 

He said no code was pulled for the transfer case. FYI, my service 4wd light went away on Saturday. Should I change the selector switch?

[[email protected]]

That sticky note right there has a code and also says to replace the switch. So IDK. I would of thought it was the encoder as that's what it is 9 out of 10 times. coo4o is the rear wheel speed sensor, BTW.

[Blue_Z71]

Yea, I checked out the 0040...don't know why that would be bad, but whatever. The quote at $98.51 for the switch is what killed me. I've seen them wayyyy cheaper. He said they'd have to order it, so I'll probably give them a call on Wednesday if you guys think this will cure my problem.

[[email protected]]

It's usually the encoder, but you can get a switch at auto parts for about 50, if it doesn't fix it, return it and buy the encoder and replace it. It could be either, but like I say, it's usually the encoder on the t-case.

[Blue_Z71]

I'll give Auto Zone a try and report back with my findings. Thanks for the help