1990 GMC K1500 4x4 and brake problems

mbarcher · 02-23-2007, 07:53 PM

I have a 1990 GMC K1500 4x4 and have the following problems ...
1- the 4x4 will not engage the front axle .... any suggestions as to why ?
2- my brake light(old abs system) on the dash stays on ... yet parking brake is off and when applies the light gets brighter. Have run a scanner on the truck and removed all the fault codes and light goes out for a while then comes back on ... any way to disconnect the abs and turn the light off ?

gmtech · 02-24-2007, 09:22 AM

Yeh check connect a test light between the 2 wire connector of the actuator on the front axle if it lights up bad actuator. The abs on your truck should just have a black box mounted next to the brake master cylinder just unplug the wires.

mbarcher · 02-24-2007, 03:18 PM

didn't try a test light , but did use a multi tester on the actuator and connected the leads to the 2 wires on unit ... showed there was contenuity between the 2 wires .
As for unplugging the wires at the master cylinder ... will that also disable the fluid level indicator for the resevoir ?

gmtech · 02-24-2007, 07:04 PM

No you need to check to see if you are getting power to the front dif actuator when key is on and in 4x4. The wires you unplug for the abs is a black box alongside of the master cylinder and it has nothing to do with the fluid level indicator

dstrick32 · 02-26-2007, 06:06 PM

Agree with unplugging the back box, it will not affect fluid level light. You will most likely have to replace the front differential activator. These need to to be used regularly to keep them from freezing up.

02-23-2007, 07:53 PM	#1
mbarcher Junior Member Join Date: Apr 2006 Posts: 8	1990 GMC K1500 4x4 and brake problems I have a 1990 GMC K1500 4x4 and have the following problems ... 1- the 4x4 will not engage the front axle .... any suggestions as to why ? 2- my brake light(old abs system) on the dash stays on ... yet parking brake is off and when applies the light gets brighter. Have run a scanner on the truck and removed all the fault codes and light goes out for a while then comes back on ... any way to disconnect the abs and turn the light off ?

02-26-2007, 06:06 PM	#5
dstrick32 Senior Member Join Date: Dec 2006 Location: Hilliard, FL Posts: 101	Agree with unplugging the back box, it will not affect fluid level light. You will most likely have to replace the front differential activator. These need to to be used regularly to keep them from freezing up. __________________ 95 Ford F-150XL 5.0 Automatic 92 Chevy Silverado 5.7 Automatic 94 Toyota Ex-Cab 4X4 3.0 Automatic

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02-24-2007, 09:22 AM	#2
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 342	Yeh check connect a test light between the 2 wire connector of the actuator on the front axle if it lights up bad actuator. The abs on your truck should just have a black box mounted next to the brake master cylinder just unplug the wires.

02-24-2007, 03:18 PM	#3
mbarcher Junior Member Join Date: Apr 2006 Posts: 8	didn't try a test light , but did use a multi tester on the actuator and connected the leads to the 2 wires on unit ... showed there was contenuity between the 2 wires . As for unplugging the wires at the master cylinder ... will that also disable the fluid level indicator for the resevoir ?

02-24-2007, 07:04 PM	#4
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 342	No you need to check to see if you are getting power to the front dif actuator when key is on and in 4x4. The wires you unplug for the abs is a black box alongside of the master cylinder and it has nothing to do with the fluid level indicator