4WD Gremlins. Help a newbie out!

[intrigueing]

I have done a lot of reading but I am at a loss of how to troubleshoot this. This is like nothing I have found on several forums. Sometimes everything works. Sometimes it switches modes without changing the dial.


Here are some of the weird symptoms. Truck is 2004 Envoy XL 115K miles.

1) Ignition on no flashing or illuminated lights on dial. Turn switch from 2hi to auto 4x4 nothing. Turn from auto to 4HI and service 4wd comes on. When this happens there is no noises from under truck.
2) Sometimes everything works normal. When it works - all lights function and no service 4wd light.
3) Sometimes the mode shifts without changing selection on dial - I think including going into 4LO!!!! Not when moving but when truck is turned off and back on.
4) When everything is working and truck is in park - switching modes 2hi-Auto-4hi will work fine for numerous rounds (can hear actuators). Then if I put it in gear and switch from 2hi to auto it is fine, but auto to 4hi will trip dash light and everything will stop working.

Got a used TCCM that someone claimed was good - still acts the same. Could this be ignition switch? I have had intermittent working cruise control, and one time the truck stayed in acc mode with the key out. How would you recommend troubleshooting this? Any ideas?

 

[The_Roadie]

Ignition switches are cheap, and so are 4wd mode switches, even from the dealer.

 

[Matt]

Ignition switches are cheap, and so are 4wd mode switches, even from the dealer.

Get one of each and you should be good to go.

 

[intrigueing]

Ignition switches are cheap, and so are 4wd mode switches, even from the dealer.

Had been dead completely for a while - realized I put #8 back in the wrong slot. Duh!

Had an extra working 4wd switch swapped them but it did not help.

I played around with the connectors on the encoder motor. Turned the ignition on and heard the actuator and encoder come to life. Maybe playing with the plugs was a coincidence? The lights on the switch were on with 4 lo and blinking 2Hi (even though the switch was in 2HI). Put the truck in neutral and went into 2HI. Was able to switch to all modes and everything seemed fine. I had the truck jacked up on the driver side. When in 4hi the wheel would spin forward freely until I spun it back slightly then it would lock. I drove the truck and was working fine for a little bit and dash light came on and all lights went off on the dial. Was in 4wd and eventually I got it back to 2wd (dry street) - but dash light is on and everything is not working again. Could I have two bad tccms that act exactly the same? Wiring issues? Ideas?

 

[intrigueing]

I bit the bullet and went to the dealer and had the codes pulled. P0327 encoder motor shorted. Dealer wanted $560 for repair. I paid for the diagnostic and left. Should I just get a used one? There is no repairing these or easy fixes right?

 

[Enderbygrandpa]

I bit the bullet and went to the dealer and had the codes pulled. P0327 encoder motor shorted. Dealer wanted $560 for repair. I paid for the diagnostic and left. Should I just get a used one? There is no repairing these or easy fixes right?

you should read manual on how to use your 4wd you are not supposed to switch into 4hi while in gear or above 3mph.

 

[hdodd1]

i used a rebuilt one, it had a life time warranty...good thing i replaced within a month but have had no problem with the second one in over two years.

 

[hdodd1]

Shifting Into Four-Wheel High or Automatic
Four-Wheel Drive
Turn the knob to Four-Wheel High or Automatic
Four-Wheel Drive. This can be done at any speed
unless you are shifting out of Four-Wheel Low. The
indicator light will flash while shifting. It will remain on
when the shift is complete.
Shifting Into Two-Wheel High
Turn the knob to Two-Wheel High. This can be
done at any speed unless you are shifting out of
Four-Wheel Low.

This is what my owners manual says about shifting into four high or AWD...into 4 lo you must be moving less then 3mph.

 

[intrigueing]

I got a used encoder motor and everything is back to normal!

 

[IllogicTC]

you should read manual on how to use your 4wd you are not supposed to switch into 4hi while in gear or above 3mph.

That's 4Lo, and it actually won't even (or shouldn't even) try to initiate the switch unless the vehicle's computer determines it's in neutral anyway.

Around here, the general suggestion is to engage A4WD/4HI at low speeds 10MPH maybe(?), but technically it's supposed to be an "on-the-fly" system used anywhere before you hit cruising speed (I'd say 40MPH, lock-in clutch engagement). That's how it's SUPPOSED to have worked, at least, before metallurgy and all that came to play.

But don't trust the manual, man. Trust the experience many have had who are on this forum. It doesn't have to be a crawl, doesn't have to be in neutral, but keep engagement to low speeds just in case.