So here's the deal, I got a 2000 ZR2 5 Speed, 4 button switch. I live in Colorado and use my Auto 4x4 pretty often in the winter. A couple weeks ago I went to switch it back to 2hi and both lights flashed, then both lights stayed lit.

Checked vacuum lines - found dry rot and cracks so I replaced them. Double checking my HVAC vents and everything is working as you'd expect.

Week goes by and I gotta use my Auto 4x4 again, Switches, engages, no problems.

Back to 2hi and it fails again - lights flash then they both go solid.

Replaced the actuator under the battery - probably a waste of money bc the old one seemed fine, except the spring seemed "janky" so no big deal.

Took it out for a test, Auto 4x4 (check) 4hi (check) 4lo (check) Back to 2hi (check)

Tested again the next day,

Engages 4hi, then it doesn't disengage. Turn vehicle off, then on and it works, I am back in 2hi.

Test auto 4x4, it switches, go to switch back....both lights flash then only the auto 4x4 stay solid. And now the switch is unresponsive.

I also have and extra dash switch that I have swapped out for testing.

Just last night I was checking my HVAC again and it seems like air the floor board isn't working, while the other controls do.

I am looking for recommendations on what my next move should be?
T-Case Vacuum switch?
TCCM? Replace? Clean connectors?
Replace cable? it moves freely, not 3/4 inch though witch I have read on the forum.
Tranfer case encoder?
Tranfer case motor?
Are those last 2 the same thing?

I love how the actuator is under the battery so that I can test it while the vehicle is running.

Thanks for any and all of your help!

 

The NV236 Auto 4WD does not have a vacuum switch on the transfer case. It has an electro-vacuum switch located under the hood in the center of the firewall, just below the cowl. If the axle actuator under the battery is working, the switch is working. Check the TCCM connectors for corrosion, and clean if/as necessary. Next step is to retrieve the DTC's with a capable scan tool, then post them in the order they are retrieved. With an intermittent condition like you're experiencing, the encoder motor position sensor, encoder motor itself, or any of their circuits, could have a problem.

 

What if u have no codes?

 

Same thing as with powertrain DTC's: no codes, no problems detected. 1998 and newer have a BCM, (Body Control Module). If the transfer case can't complete, (or doesn't complete), a range or mode shift, C0387 will be set in the BCM. The switch light will blink, and the TCCM will command the encoder back to the original position that it was in before you tried to change it. The only way to retrieve transfer case DTC's is with a scan tool capable of accessing the BCM.

 

The 236 is a fun little animal with known issues with TCCM failures. It is also not unheard of for the encoder motor to get weak and not want to switch either into auto/4wd mode, or out back into 2wd. My suggestion is to pull the TCCM out and clean all the connections, pack with dielectric grease and try again. If that fails, most likely the encoder motor is weak...unfortunately, they are not cheap. Either way, you need to be able to see what codes are stored.

 

If there are codes, a SES light will come in or no? I think I remember seeing something about the indicator lights flashing, am I right?

my issue is 2hi works, if I go to 4hi or auto, they just keep flashing. Btw, 2001 4x4x4 4-button system,.,

 

SES light will not come on, it indicates issues with the engine & transmission only. The lights in the 4WD switch will flash if there's a problem, and then the service 4WD light in the instrument cluster will come on indicating there is a DTC in memory.

 

Hope my problem is simple, dont have the Service 4wd light.

 

Might be a DTC in the pending file and it might give a clue for diagnosis. (DTC's in the pending file do not turn the light on).

 

I've checked pending codes and nothing is there...