so last year I replaced the dash switch and the module in the kick panel and everything worked dandy.

this is the 4 button version

what happens now is this..........

car is in 2HI - I press 4HI or AWD and the button keep flashing, I hear the kick panel module switching but I do not hear of feel any mechanical engagement of the front wheels. After flashing for a min or so (on AWD or 4HI), the 2HI light comes back on.

When I press 4LO button, it flashes, I do hear and feel transfer case shifting into low gear but still no 4x4 and 4LO button just keeps flashing forever until I hit 2HI and I can hear 4LO disengage and go back to 2HI.

Service 4WD light comes on sometimes randomly and sometimes it does not come on even when I try and fail to engage any sort of 4 wheel action.

what do you guys think? is it he transfercase motor or the vacuum ball under the battery?

------------------UPDATE------------------------

found the problem. it was a broken vacuum hose that goes from the solenoid located on the firewall to the vacuum ball under the battery. bought 6 feet of new hose, replaced the old one and 4x4 is back in action.

In this pic it was the hose which goes to the left side that was damaged (to front Axel)

 

Sounds like a problem with the encoder motor to me, but you should get the TCCM scanned for codes to make sure. There may be some failed shift codes that would give some direction to the diagnosis. A full feature scan tool can be used to monitor the encoder states to see if the motor is even moving the shift sector shaft in the transfer case properly.

 

thanks so much for replying to this thread!!

encoder motor is the actuator motor on the transfercase?

another stupid question - TCCM scanner is not same scanner that read engine codes, is it?

 

The encoder motor is the motor that is on the transfer case.

Scanning the TCCM requires a scanner with Enhanced GM OBD2 diagnostic capabilities. Not all scanners have this feature. I use an AutoEnginuity scantool (PC Based software with an USB to OBD2 dongle), but this option is quite often too expensive for the casual DIYer. Many of the more expensive units that shops use can do this provided the tool has the appropriate programming & the operator knows how to use it. It's sad to say that most shops use their $1000-$2000 scan tools as a generic OBD2 scanners only and use the "throw parts at it" method of troubleshooting, but that is another subject entirely.

One thing you could try is to measure the resistance on the motor + & - feeds at the encoder motor connection in a 'cold' state (after it has sat for a while) and then again in a 'hot' state (just after a failed shift). Basically, this test looks at the motor windings. Since the windings are a continuous loop of wire (or should be), there should be an associated resistance. I have effectively diagnosed quite a few weird acting transfer cases using this method of confirmation after other tests had already pointed me to a bad encoder motor. It is often something that owners understand better than "See there (looking over my shoulder at the computer screen with a bunch of numbers on it), the encoder motor channels didn't change after a commanded shift and they should have".

If the 'hot' state reads an infinite resistance (open connection), then the motor is bad and the encoder motor assembly needs to be replaced.

 

I guess my best bet is dealership, as sad as it is. Living where I am I dont think anyone around here is very knowledgable on this type of thing.

another stupid question - to read TCCM codes, do I use the same harness located under the hand brake on the driver side? or is there a separate harness for the TCCM?

 

A transmission specialty shop is a good option in lieu of a dealership & the codes are read through the same OBD II connector.

 

Check my edit above. I must have been typing that out while you were responding. You can test the encoder motor windings yourself to see if the motor is actually good. In the case of the NV236 encoder motor, you also have a brake winding (electro-magnet) that, when energized, disengages the motor brake assembly. This can be tested in much the same manner.

The thread linked to below (from the Tech Article DIY Index) will give you the appropriate wiring information:
NV236 Wiring & Diagnostic Information

And yes, the same OBD2 connector is used for all scan-tool diagnostics.

 

ok thanks a lot. I will focus on the encoder motor.

I have a chance to just purchase one for $40, do you think I should just do that? How hard is it to replace it?

 

------------------UPDATE------------------------

found the problem. it was a broken vacuum hose that goes from the solenoid located on the firewall to the vacuum ball under the battery. bought 6 feet of new hose, replaced the old one and 4x4 is back in action.

In this pic it was the hose which goes to the left side that was damaged (to front Axel)