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Blinking 4 Wheel Drive Light?

haulincats

By haulincats
in Ask A GM Technician

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haulincats Enthusiast

haulincats

Posted
Posted

I have a 1996 GMC 1500 Sierra 4 x 4 Pickup with the

push button 4 wheel drive.

When I push the 4 wheel high or 4 wheel

low button the light on the switch just blinks.

It is not going into 4 wheel drive.

Where do I start looking for the problem?

I don't want to just start swapping parts.

Thanks,

Vance

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

glad your not gonna throw parts at it,get it scanned by a real scanner ,they live at the dealer,get a diag,pay for it and get the part thru a jobber parts store if available or get it fixed while its on the hoist ,your choice.

2COR517 Enthusiast

2COR517

Posted
Posted

It is MOST likely the front axle actuator. And I presume you can hear the case going into 4Lo. But check your 4wd fuses first.

 

Here's how you can test the actuator. Leave the ignition on. With the case in 2Hi, you should be able to spin the front driveshaft. With the case in 4Hi, you should not be able to spin the front driveshaft. Leave the case in 4Hi and jack up the right front tire. You will probably be able to spin the right tire. Now the final test. Turn off the key. Pull the front axle actuator. Its on the pass side of the pumpkin, on the extension housing. Back side, near the top. Has two wires connected to it, and a big hex. Disconnect the wires, and pull the actuator. Hook the wires back up. You can measure the length from the flange to the inside end of the actuator, or just eyeball it. Turn the key on. The actuator is probably not going to move. Test for voltage at the wires. If you have voltage, and the actuator isn't working, it's toast.

haulincats Enthusiast

haulincats

Posted
  • Author
Posted
It is MOST likely the front axle actuator. And I presume you can hear the case going into 4Lo. But check your 4wd fuses first.

 

Here's how you can test the actuator. Leave the ignition on. With the case in 2Hi, you should be able to spin the front driveshaft. With the case in 4Hi, you should not be able to spin the front driveshaft. Leave the case in 4Hi and jack up the right front tire. You will probably be able to spin the right tire. Now the final test. Turn off the key. Pull the front axle actuator. Its on the pass side of the pumpkin, on the extension housing. Back side, near the top. Has two wires connected to it, and a big hex. Disconnect the wires, and pull the actuator. Hook the wires back up. You can measure the length from the flange to the inside end of the actuator, or just eyeball it. Turn the key on. The actuator is probably not going to move. Test for voltage at the wires. If you have voltage, and the actuator isn't working, it's toast.

 

Yes I can hear the case going into 4 lo so does that mean the transfer case motor is

working?

Thanks,

Vance

2COR517 Enthusiast

2COR517

Posted
Posted
Yes I can hear the case going into 4 lo so does that mean the transfer case motor is

working?

Thanks,

Vance

 

 

Yes sir. Do the test I outlined and you should be able to confirm it in less that 30 minutes.

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