Hi All,

I have a 99 GMC Sierra Z71 4X4, 5.3L, Auto, Short box

My ABS unit is activating prematurely, meaning when I depress the brake
pedal, the ABS unit thinks I am really laying on the brakes and the unit
should activate, I took it in to get it scanned, nothing abnormal came up
on the computer for codes, the mechanic determined that the wheel sensors
probably need cleaning (and\or) replacing

My question is...

Is this an expensive job? He told me that some trucks have the sensors
built into the hub and if it can't be cleaned, the hub has to be replaced,
he wasn't sure whether my truck was this type

Has anyone experienced this before? its going in next Tuesday to get fixed

PS, I already had replaced the whole ABS unit once on this truck in 2003,
about 40K ago (very expensive)

Thanks in advance for your help (comments)

Brian

99 GMC Z71 wrote:
Rust between the sensor and the hub. VERY common problem.

Yep, BTDT more than once.


its going in next Tuesday to get fixed
You can DIY if you have a few tools.
All you need to do is pull the wheel/tire off. Then turn the wheel so
the sensor is out some. Then go in with a wire brush and clean around it
REAL well. Now you remove the bolt that retains the sensor, Then GENTLY
stick a plug in the hole (make one out of a sharpie marker) Then clean
off the rust and crud from the sensor and around the hole. Be GENTLE
with the sensor, the wires are not that hard to break. Clean the tip off
with some cleaner and once you have it all clean put a THIN coat of
silicone grease on the Oring and slip it back in place. Tighten the
retainer bolt down and then spray some paint around the sensor to seal
it some. I also take an acid brush and coat around the sensor with some
RTV. Keeps the water/dirt out to slow the rusting.


--
Steve W.