Check out the shift motor, that was my culprit, clean connections, check for broken wires, and switch it into 4 hi then tap the motor with something, or listen to see if its tryin to work, you can hear it switching,if not probably bad, it should try at least 3 times; Was the tccm programmed for your transfer case?? got mine from boneyard supposedly a plug and play type deal, it wasn't, dealer fixed it, it was for a 244 not a 233

 

Eric, don't really know about the programming. Supposed to be for my truck but that's a good point. If I start and shut off the truck a number of times, sometimes the shift motor does work. I did check all the connections at the motor and they were fine. Most times I get no lights on the switch when I turn the ignition to on position (Eng, not running) Used to get lights on switch in this position and was able to shift the differential without the truck running. I hate to take anything to a dealer as they usually charge ridiculous prices.

 

Sandman,

Intermittent problems s*ck.

Can you chase some wires? Try to find out why you don't get lights all the time when you turn on the ignition.

At the TCCM: Connector 3 (small 4 pins) the Light Blue with Red tracer should be 12v - constant.

At the Switch: Pin 7 Dark Blue with a white tracer, 12v, switched by ignition switch.

It could be a bad ground as well. All the grounds for the transfer case go back to the center of the instrument panel. The grounds are near the diagnostic junction port, bolted to the instrument panel frame. Make sure they're clean and tight.

 

Dakota Dan thanks....I'll check those areas. I've found something really weird today while trying to figure out what is going on here. If I turn the ignition on....motor off, I get no lights on 4 WD switch. But I do not get a door ajar light even with 2 doors open. The chime goes on for about 5 minutes or so then stops, the door ajar light comes on and now so does the 4 WD switch. I can then cycle the motor into 4wd hi and low. Now if I turn the ignition switch to off and back on again....no 4 wd. If I leave it on...once again in 5 minutes or so the same thing happens and I have the 4 wd switch working again. I've had on and off issues with door ajar not going off when doors are closed. Also, recently the dome light didn't shut off and killed my battery. I know some have said Central Timer has nothing to do with it but I found some threads on another forum which say different and changing it out solved the 4 WD switching issue. I do not put anything past modern cars as if I unplug the mirror on my chevy S10, it runs like crap....go figure?

 

Sandman,

We might be on to something here.

The central timer AND the TCCM use the same ground. The one I told you near the diagnostic port.

If you follow the harness the ABS module plugs into you'll find two ground locations. Make sure they're clean and tight.

Disconnect the battery before you do anything here.

 

Dan, thanks

I'll check the grounds today and report back. This one has really got me scratching my head.....I long for the days of the mechanical transfer case shift.

 

Dan

I checked the grounds and were clean and tight. I cleaned the connections at the central timer also....still no difference. Not really sure what to do next.

 

I'm running out of ideas Sandman.

I see no connections between the CTM and the TCCM except, like everything, they are on the PCI bus.

Everything else works when this happens?

Might be time for the dealer. They can plug the DRB into it and see if what's going on with the TCCM and CTM.

I'll keep thinking about it. Good luck.

 

The weird part is you can get different results by turning the ignition on and off. It will work one time and continue to work until I turn the igntion off then it won't work. If I wait awhile with the switch on, the chime goes on for about 5 minutes and then stops....then the 4 wheel drive switch comes on and works.... I did find water on the floor directly under the CTM so the truck has a water leak somewhere on that side. So things I've tried so far:

* Replaced TCCM
* Checked switch connections and wires
* Checked and cleaned mode sensor and shift motor connections.
* Unplugged CTM and cleaned connections.
* Checked and cleaned ground wires.
* Unplugged Battery for 1/2 hour and reconnected. (Some have claimed this resets CTM??)

Nothing, nada.....same results. If I had any hair I'd be ripping it out by now!

 

Time to check the ignition switch. There is a set of contacts that feeds part of the CTM and the TCCM. It also does things like the overhead console and auto day/night mirror if you have those.

Can you check, it should be fuse 11, a 10 amp in the JB for the TCCM. Make sure it has power when all this stuff is happening with the chimes/transfer case.

Use a test light if you can, not a meter.