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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
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Experience:  GM Grand Master Technician 2007. 14 years experience.
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1996 Chevy: z71..4wd..I shift to 4H or 4L the indicator doesnt come

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I have a 1996 Chevy k1500 z71 with manual 4wd on the floor. When I shift to 4H or 4L the indicator doesnt come on and the truck definately doesnt go in to 4wd. What could be the issue? Please be specific as I just bought this truck and it is my first 4wd ever.

Welcome. There are a few possible causes. The first is the switch on the transfer case just above the shift lever. This sends power to the front diff actuator to engage the diff.

Check the 4wd fuse in the left dash fuse block. If that is blown, then the front axle actuator is likely damaged. Once they short out, they pop that fuse. This actuator is threaded in the front right of the diff housing.

Customer: replied 6 years ago.
there is no "guts" in the place where the transfer case fuse is supposed to be. I checked the fuse first.

How about the 4wd fuse in position 24?

Customer: replied 6 years ago.
all fuses checked and good with proper fuses installed

OK, do you have a test light?


Customer: replied 6 years ago.
I dont think I do, but I do have a Fluke digital multimeter
That will work. Test for 12v with the key on at the brown wire at the connector on the top of the transfer case. If there is power there, put it in 4wd and check the front diff for power on the light blue wire. If there is power, then replace the actuator. No power, replace the switch.
Customer: replied 6 years ago. the brown will be the switch and the blue the actuator? or vice versa? Sorry I am being difficult, I just have no clue and dont want to make things worse
Brown is power and the switch sends power to the blue when in 4wd.
Customer: replied 6 years ago.
ok, I will check it first thing in the morning as it is almost 1AM here. Thank you for your help

OK, its late here as well. Sleep well.


Customer: replied 6 years ago.
as far as I can tell I have power to the connector on top of the transfer case, not sure which color wire though, it is the middle connection. There is no power at the front diff on the light blue wire however.
OK, I would replace that switch. If you had the key on, the shifter in 4 and there is power on the brown, then that or a bad wire is likely the issue.
Customer: replied 6 years ago.
yes, key on, transfer case in 4H and power to the center terminal on the switch on top of the transfer case. I just remove the upper switch, replace and check all again?
Tell you what, use a small section of wire and jump the brown to the blue and see if the front axle engaged.
Customer: replied 6 years ago.
are they on that same switch connector?

again, my apologies, I cant tell what color is what on the switch connector.......
Yes, these are in the same switch. Middle is the blue so jump the power one to the middle one.
Customer: replied 6 years ago.
the middle is where I have power with the key 2wd and 4wd
OK, hold on. I misread the schematic. You have no power elsewhere? That is the 4lo indicator. We need to go back to the power. IF you have a section of wire, try running a power wire from the battery to the brown wire. You will need to use light to make sure you go to the proper wire.
Customer: replied 6 years ago.
the only power is on the middle terminal of the three terminals in the connector. I will try to find what color each is
The 3 colours are brown, which is power, light blue which is to get power in 4wd and grey black which sends a signal to the PCM for 4lo to change the shifting.
Customer: replied 6 years ago.
yes, and brown is the center terminal, that is where I am getting voltage

Ok, that does not make sense. Center, terminal B is grey black.

Look at the lower left of the schematic.

Object Number: 484577  Size: FS

Customer: replied 6 years ago.
it isnt making sense to me either, I have thoroughly cleaned the wires and the center is the gray/black(not brow as originally state, my apologies) which per your schematic is incorrect as well........

It may be that a repair was done, and honestly if the schematics were always correct, my job would be easier.

Try jumping the power wire to the blue and see.

Customer: replied 6 years ago.
ok, I will definitely be giving EXCELLENT feedback for your time and patience with me, I am 4wd stupid as this is my first 4wd ever. Do I need to leave the connector attached to the switch when I do this? Or can I unhook and jump it from there?
Unhook it and jump it.
Customer: replied 6 years ago.
ok, be back shortly.....
Customer: replied 6 years ago.
ok, after further check, brown is hot and gray/black is hot, I will now jump from brown to blue......

yes Brown to Blue.


Customer: replied 6 years ago.
sorry for the delay, brown to blue produced no results
OK, with them jumped, check the blue at the front axle actuator for power.
Customer: replied 6 years ago.
there is power to the blue at the actuator
Then you need the front axle actuator of there is power and it does nto engage the front diff.
Customer: replied 6 years ago.
okay, is it a dealer only item or can I get it at a parts store?
Any parts store should have this.
GM Tech (Cam) and 4 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
okay, thank you very much for your time and patience with me through this.

My pleasure. To get me directly the next time, in the title line put "For BlueGorilla Only" and I will get it as soon as I am able.

Customer: replied 6 years ago.
awesome, thanks again
Customer: replied 6 years ago.
where do I find the axle code? there are 2 diff. actuators for my truck...... =o )
The 2 types are the thermal actuator that has a pigtail and 2 wires going out if it or the updated one that has a motorized actautor and a plug that goes into it. They should be able to find it using this information.
Customer: replied 6 years ago.
AutoZone is stupid, they told me I had to have the axle code.....hahaha

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