'96 k1500 - no 4x4

[Mikebuild]

Trying to diagnose 4x4 problem. '96 k1500 auto trans, push button 4wd.
When I hit the 4H button, it flashes while the 2H stays illuminated and you hear a "click" under the dash (like a relay or something, normal when the 4x is working). The 4H light flashes for ~2-4 seconds then quits. I've bench tested the actuator and it will engage with 12 volts. I check for power at "it's" connector (with the key on) and have no power. I also tried pushing 4H button and still no power at the actuator. I've checked the 4x4 and tc fuses with ohm meter...both ok.

??????

When you hit 4H button, what is the sequence of action that takes place with a properly operating system? (step by step)

I see 3 different electrical connections on the transfer case, what are these for?

I can feel another connection on the front differential, above the actuator, what is this one for?

I see 1 "motor?" on the transfer case, what is this?

Is 4x4 controlled by a computer of any sort?

Is there a good diagnostic website available for this topic? or maybe some other threads on this board?

Also, awhile back, when 4x was still working, it got stuck in 4L. After a day or so, it finally went back into 2H. From then on, the 4x hasn't worked.


Thanks.

[MT-2500]

What engine trans and transfer case?
If a 233/243/ transfer case jumper pin 13 to ground and turn key on and read the codes on shift lights.
Count the flashes on each one and post back>
Mt-2500

[777stickman]

I'll try to answer some of your ?'s. Yes the 4wd system is computer controlled by the "transfer case control module" (tccm) located left of the steering column under the dash. The motor on the t-case is part of the actuator assy (motor encoder assy).

When a selection switch is pressed it sends a signal to the tccm which sends a signal to the t-case actuator and the front axle actuator. When these actuators are in the commanded position the lights stop blinking and remain steady on for the commanded position.

The most common causes for 4wd failures are 1) the t-case actuator, 2) the tccm, 3) the selector switches, 4) wiring.

The best way to diagnose this system is with a scan tool that gets beyond generic codes.

Also there are 4 fuses involved. 1) TCASE, 2) 4WD, 3) GUAGES, 4) ILLUM. Fuses are cheap, don't just check them, replace them, although I don't think that's your problem.

[Mikebuild]

Originally Posted by MT-2500

What engine trans and transfer case?
If a 233/243/ transfer case jumper pin 13 to ground and turn key on and read the codes on shift lights.
Count the flashes on each one and post back>
Mt-2500

Thanks for the help. Pardon my ignorance.
5.7L, 4L60, 243

Where is "pin 13" located? Connector under steering column? If so, they are not numbered, so ... count left to right/top to bottom?

Is this refered to the "OBD"? or something else?

Thanks again.

[2000CAYukon]

Originally Posted by Mikebuild

Thanks for the help. Pardon my ignorance.
5.7L, 4L60, 243

Where is "pin 13" located? Connector under steering column? If so, they are not numbered, so ... count left to right/top to bottom?

Is this refered to the "OBD"? or something else?

Thanks again.

This has a diagram of the pin numbers for the OBD-II connector http://www.obd-codes.com/faq/do-i-ha...ii-vehicle.php

//2000CAYukon

[Mikebuild]

Originally Posted by 2000CAYukon

This has a diagram of the pin numbers for the OBD-II connector http://www.obd-codes.com/faq/do-i-ha...ii-vehicle.php

//2000CAYukon

Thanks Yukon.

I grounded pin 13 and got no response from the lights.
They (all 3 of them) came on for a second when the key was turned to the "on" position, then they went out. When I "ungrounded" pin 13, 2H light came back on (as normal). They never blinked in a pattern.

I came across something about "cold solder joints" on/at the switch assembly. How do you check for that?
Thanks.