Stuck in 4WD. Any help?

[TheEnder53]

It is the same shape. The issue is that the encoder motor makes the same sound as the old one, and doesn’t change positions when i try to select it via the dash selector, and the vehicle will only shift into 4lo/4hi with a crescent wrench.

Thing that stumps me is that both old and new encoders were at the same location of the female end of the shift shaft on the encoder. Yet I now cannot get either back on with the TC in the original position (4HI). So I am a bit stumped with that.

Forgot to mention. Selecting 4HI with the new shift motor resulted in just the same 2 buzzes and it never moved.

 

[rockola1971]

Need year and trim level so I can dig up schematic of the 4wd for your ride. What does the RPO code show for your TCASE? NP8?

 

[TheEnder53]

Need year and trim level so I can dig up schematic of the 4wd for your ride. What does the RPO code show for your TCASE? NP8?

Yes.

It is a 2001 Tahoe LS 4X4.

 

[TheEnder53]

Got the new encoder in. Cleared all fault codes, no Service 4X4 on dash anymore. Tried to shift into 2HI and it failed immediately, and threw C0324 again.

What gives?

 

[Fless]

I don't know that the values in the link below are correct for your year, but you might pull the dash switch and clean the contacts, or replace the dash switch with a new one for your model year and T/C. A good bi-directional scanner would help you see what's being commanded vs. actual.

“Service 4WD” message

Switch measurement procedure here, starting at about 2:10 into it. Auto4WD = 61.7-68.1 ohms 4HI = 656-760 ohms 2HI = 1.50-1.53 K ohms 4LO = 2.32-2.37 K ohms Neutral = 1.015-1.035 K ohms Pics of switch internals. On the last pic, reflow the solder on the pins in the rectangles, and clean the...

www.tahoeyukonforum.com

Are you able to freely move the transfer case shaft to the different positions with a wrench or channel-lock pliers? I assume your T/C shaft has the two flats, and not the newer "star" end.

 

[TheEnder53]

I don't know that the values in the link below are correct for your year, but you might pull the dash switch and clean the contacts, or replace the dash switch with a new one for your model year and T/C. A good bi-directional scanner would help you see what's being commanded vs. actual.

“Service 4WD” message

Switch measurement procedure here, starting at about 2:10 into it. Auto4WD = 61.7-68.1 ohms 4HI = 656-760 ohms 2HI = 1.50-1.53 K ohms 4LO = 2.32-2.37 K ohms Neutral = 1.015-1.035 K ohms Pics of switch internals. On the last pic, reflow the solder on the pins in the rectangles, and clean the...

www.tahoeyukonforum.com

Are you able to freely move the transfer case shaft to the different positions with a wrench or channel-lock pliers? I assume your T/C shaft has the two flats, and not the newer "star" end.

Yes, it has the 2 flats.

I can freely get it into 4hi or 4lo. I’m not sure which way i’m supposed to move it to get it into 2hi, but either way i spin it results in it not spinning anymore. Just gets stuck. I will test it out more. For right now, it drives fine without the front driveshaft.

 

[TheEnder53]

Followed the instructions on the service manual. Disconnected the TCCM & Encoder and hooked up a test light connected to ground.

Probed encoder motor lock solenoid control wire (Pin D, Connector C1) for short to voltage - did not light up. Pin D lit up, just to be sure it was getting constant voltage.

To make sure I was getting the correct reading, I probed connector E1 (Tan, Lock solenoid control) on the orange connector for the TCCM. Again showed up nothing. So that rules out wiring.

New TCCM on the way. Will be in in around 12 hours.

 

[TheEnder53]

I don't know that the values in the link below are correct for your year, but you might pull the dash switch and clean the contacts, or replace the dash switch with a new one for your model year and T/C. A good bi-directional scanner would help you see what's being commanded vs. actual.

“Service 4WD” message

Switch measurement procedure here, starting at about 2:10 into it. Auto4WD = 61.7-68.1 ohms 4HI = 656-760 ohms 2HI = 1.50-1.53 K ohms 4LO = 2.32-2.37 K ohms Neutral = 1.015-1.035 K ohms Pics of switch internals. On the last pic, reflow the solder on the pins in the rectangles, and clean the...

www.tahoeyukonforum.com

Are you able to freely move the transfer case shaft to the different positions with a wrench or channel-lock pliers? I assume your T/C shaft has the two flats, and not the newer "star" end.

I got the new encoder both hooked up to the TC and hooked up electrically.

New TCCM is installed as i tested wiring integrity to verify it was good.

Now, the issue is that the new TCCM is throwing code U1000. It takes a good 5 minutes from the time i turn the key to RUN for all of the lights to go out on the 4WD switch. Getting farther, but still, stuck.

It shifts beautifully between whatever gear I select after it eventually works. No issues.

 

[HardyHoe]

Correct me if any of this isn’t the case:
>you drove in auto 4WD
>couldn’t disengage & return to 2WD
>4 Hi became engaged (or at least the indicator light) after driving for a couple days in Auto 4WD?

Do you have the heat driven 4WD Actuator that locks the hubs? I’m not sure what year you said you had.

 

[Fless]

Do you have the heat driven 4WD Actuator that locks the hubs? I’m not sure what year you said you had.

He said 2001 Tahoe LS 4X4 in post #13.

@TheEnder53 what TCCM did you get? I know the later Tahoes need to have them programmed, or be purchased as not needing to be programmed. Not quite sure about yours.