Service 4wd

[brycetyree702]

Any Ideas? Truck won't go into 4HI. It will however go into Auto 4wd, 2Hi, and 4Lo. I get a service 4wd light on the dash every time I put it in any option but it works perfectly unless I press 4HI. I just put a new transfer case encoder motor in. I put a new front differential actuator in and switch seems to be operating correctly. I can hear the encoder motor trying to shift into 4Hi and the switch blinks, then goes back to Auto 4wd. Goes solid and locks into Auto and 4Lo. 2hi has no issues. 2003 Tahoe

 

[Sam Harris]

I’m wondering if the work you did has something to do with it not functioning 100%. Of course I don’t know what it was doing before you did the work either?

 

[rockola1971]

Pull Tcase shift motor and then cycle dash 4wd pushbuttons and see if the shift motor moves to position.

 

[brycetyree702]

I was forced to use the 4wd yesterday during our storm here in Iowa. Next thing I know the thing is stuck in Auto 4wd now. The service 4wd light is still on and I have no movements from the encoder motor or the actuator. Chances of it being the switch since both those parts are less than a month old? It was working when I put it on and the 4wd was only used twice since.

 

[brycetyree702]

I’m wondering if the work you did has something to do with it not functioning 100%. Of course I don’t know what it was doing before you did the work either?

Before I did the work it was partially engaged and it was blowing the fuse. No lights on the switch. Replaced the actuator on the front diff and the encoder motor on the transfer case. After that the 4Hi didnt work and everything else did. Now its stuck in auto 4wd after the snow storm yesterday.

 

[rockola1971]

Before I did the work it was partially engaged and it was blowing the fuse. No lights on the switch. Replaced the actuator on the front diff and the encoder motor on the transfer case. After that the 4Hi didnt work and everything else did. Now its stuck in auto 4wd after the snow storm yesterday.

Are you sure its actually in Auto 4wd or is the light just lit up showing Auto 4wd? Just because the light says its in X mode, doesnt mean it is actually in that. Ive seen them show 4w Lo while driving 55mph.

 

[brycetyree702]

Honestly I dont think it's actually in auto 4wd. I got stuck yesterday and I managed to get out, but I was spinning the rear tires the entire time. Do you think it's possible that it is just the switch?

 

[rockola1971]

Honestly I dont think it's actually in auto 4wd. I got stuck yesterday and I managed to get out, but I was spinning the rear tires the entire time. Do you think it's possible that it is just the switch?

Honestly since its showing that it is in Auto 4wd but it sounds as if it is not then that tells me that the wrong feedback signal is getting to the switch indicator lights. That signal comes from the commutator (AKA Encoder ring) that is inside the Tcase shift motor.

Your prior fuse blowing on the original shift motor points to internal short to ground and/or wiring harness problem going to the shift motor. Inspect wiring harness for damage, especially at points near the frame or sharp metal on its path forward to the 4wd module.

 

[brycetyree702]

Honestly since its showing that it is in Auto 4wd but it sounds as if it is not then that tells me that the wrong feedback signal is getting to the switch indicator lights. Thats signal comes from the commutator (AKA Encoder ring) that is inside the Tcase shift motor.

Your prior fuse blowing on the original shift motor points to internal short to ground and/or wiring harness problem going to the shift motor. Inspect wiring harness for damage, especially at points near the frame or sharp metal on its path forward to the 4wd module.

Alright yeah, Ill have a look and go from there. Thanks, Ill let you know if I find anything.

 

[George B]

You need a bidirectional scan tool to help you diagnose this.

Or...