ABS & parking brake light always on.

[DennisTheMenace]

Hi guys, I am having an issue with my 03 silverado (extended cab, 4x4, 5.3L, 135k miles) where my parking brake and abs light on the dash are always on.  The braking performance has been fine.  I came across some diagonistics which said the ABS module has a bad ground.  I have recently cleaned up the ground a lot which had no impact on the lights.  I haven't had the codes read yet.  Any ideas what might be causing this?

[Jsdirt]

I don't work on too many GMT-800s, since they don't break as often, but on the 900s, the ABS unit is underneath the driver's side seat bolted to the frame. Thanks to GM's brilliant engineering, it gets peppered with corrosive road salt - what usually happens is, the entire guts of the unit will become a giant green crust, and short circuit internally. You can replace the module separately from the ABS unit itself, but sometimes when they're real bad, it makes better sense to replace the entire thing as one assembly. The tiny bolts will usually break off inside the unit, and make this job a nightmare.

 

Before condemning the unit, check all powers and grounds to the module. Look for any blown fuses. Remember, the ABS motor uses a the large Maxi fuse, usually 60A - I've seen those blow due to short circuiting keeping the motor running non stop, whether the key is on or off.

[riverbanks]

Had a damaged wire to wheel sensor do the same thing,wrong wheel weight on inside of rim clipped the wires,broke the wire bracket, stretched the wires

[davester]

get the codes read and start from there...  Everything else is just throwing parts & time at it and hoping it goes away.