Here's what I mean by check all the fuses!

For the 3-button transfer case
https://blazerforum.com/forum/2nd-ge...-blazer-89670/

TCCM has one connector
Switch Panel has 2 connectors

ATC fuse (hot at all times) feeds TCCM at connector pins D14 and D15 (wire is orange)
Crank fuse (hot while cranking) feeds TCCM at connector pin D16 (wire is purple)
BTSI fuse (hot in park/neutral) feeds TCCM at connector pin D2 (wire is light green/black)
4WD fuse (hot in run) feeds TCCM at connector pin C8 (wire is brown)
Courtesy fuse (hot all the time) feeds TCCM at connector pin C6 (wire is orange)

4WD fuse (hot in run) feeds Switch Panel at C2 connector pin C (wire is brown)
Illumination Fuse feeds Switch Panel at C1 connector pin H (wire is grey)


For the 4-button (auto) transfer case
https://blazerforum.com/forum/2nd-ge...-blazer-89044/

TCCM has two connectors C1=orange C2=black
Switch Panel has two connectors

ATC Fuse (hot at all times) feeds TCCM at C2 pin D (wire is orange)
Crank fuse (hot while cranking) feeds TCCM at C1 pin E11 (wire is purple)
4WD fuse (hot in run) feeds TCCM at C1 pin E10 (wire is brown)

4WD fuse (hot in run) feeds Switch Panel at C2 connector pin C (wire is brown)
Illumination Fuse feeds Switch Panel at C1 connector pin H (wire is grey)

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Just start by pulling the connectors off of the TCCM and the Switch Panel and making sure you have power to all the right pins at all the right times.

 

Thanks Les,

2005 Jimmy, 3 button system ( no auto button) no LED,s light up. Runs in 2hi. I have pulled battery tray and cleaned two wires connected to the body, one parallel to the other. I have cleaned the wire harness going to the TCCM using the small paper clip and electrical contact cleaner to rid any corrosion. There was a slight green film on the back of harness where wires go in but I cleaned it all off. The abs has stopped as well and I wonder if the somehow related issue. All fuses checked and good. It just passed the emissions test.

The front hub was replaced by a mechanic a couple years (10,000 miles) ago. Im not sure if sensor that affectws the abs on the wheel hub has also affected the 4x4 mode(switch and TCCM)

 

great info... i will try to follow diagrams.Been a long time sincve trying to go over schematics. I was unable to get any lights to light up after following instructions and grounding out pin 13. Thats why im trying to figure what feeds those lights. Could be switch?

 

The status lights in the buttons are controlled by the TCCM. I suspect that you have no power at the TCCM from the ATC fuse or the 4WD fuse. Yes, ABS shares some circuits with the 4WD IIRC. I'll look it up.

OK, the 4WD fuse supplies voltage through SP200 and the front axle switch to tell the Electronic Brake Control Module when the vehicle is in 4WD. That's the only connection I can find between the two. But check the voltage from the 4WD fuse at both the TCCM and the Switch Panel connectors.

You can also do most of the testing with a simple test light hooked to a ground (if you prefer that).

 

Will do. Thank you. One more rookie question. The ground lead from volt meter goes to the connector ground as I test each pin or to some chasis ground (frame or bracket) that will allow reading? Thank you.

 

Just hook the ground lead to a good clean chassis ground somewhere - at least for now. Good luck.

p.s. you should be able to read the numbers on the connectors themselves, in addition to the wire color being correct.

 

Checked all pins on tccm harness. All good. Dont have a wire at c2 though.

I short out pin 13 on the DTC to see if any codes disply by flashing LED,s on switch. No lights light up. Could all thios be my dash switch? Would that be enough to keep it locked into 2hi?

 

took off dash switch. engine off. 6v across all led,s. Engine on-12volts across all LED,s but won't light up. Only the white illumination led lights up. None of the 3 that show what drive mode im in light up. Switch is good then ? Why is the led not working? Is the used TCCM I picked up junk too?

 

Only A2 had power 12v going to it.(blue 8 pin ) harness

 

yes. I checked it twice with power on and off