My 96 K1500 will not go into 4W High. The 4WD High light keeps blinking. Originally my problem was it would not shift into 4-wheel drive at all. I replaced the 25-amp fuse, front drive actuator and transfer case switch and now it does shift into 4W Lo (light on and front axle engaged), but not 4W Hi. The front axle actuator was upgraded to the new solenoid style (pn26060073) and appropriate wiring harness.
When I select 4W High (from 2W High), I hear a noise from the transfer case encoder motor but the front axle actuator never gets powered to engage. I know the transfer case switch is good as it was replaced and activates during 4W LO selection. Also, I verified the 4WD High selection switch on the dash is good (measured at the TCCM). I checked for error codes and there are no DTC codes stored in the TCCM. I am now focusing my troubleshooting on the transfer case encoder. I have wiring schematics and but they don't indicate what signals levels or "states" I should have out of the transfer case encoder for a 4W High selection. My diagrams show Encoder Channels A, B, C and P.
Can someone tell me what happens inside the transfer case during a 4W High selection and what the transfer case encoder signals should be at that time? Is the encoder assembly servicable without removing the transfer case? Any ideas would be appreciated.