1999 Chevy Tahoe 4dr 4wd. Brake light comes on when pedal is slightly pressed then off again when pressed in more then on again when fully pressed.. Has a new switch and the problem occured before a new switch was put in..the light boards in the rear were also replaced but problem still persists.... Where do I go from here?

Purge or bleed out all old brake fluid from the system start in the back right rear and then proceed to bleed the left rear then right front and finally the left front ( usually 4 to 5 bleed out cycles for the backs and 3 to 4 bleed out cycles for the front will do it). After bleeding the system out if the problem still persists and you are sure the brake shoes and front brake pads are good and have plenty of brake pad material left in them you should replace the master cylinder, if the pads or shoes are worn down replace them first before the master. Occassionally I have seen master cylinders that have weakened or fatigued cup seals inside that can cause this symptom you describe.

Hi


To start with check the Speed Sensor on the front and rear. Usually the issue is with the rear speed sensor which can be replaced easily and will cost you around $25-$40. There is a sensor at the top of the rear differential for the ABS system. When the ABS sensor on the diff goes bad the Speedo no longer will work, the odometer stops recording mileage and both brake and ABS light comes on. You also loose O/D or "Lock-up" in the torque converter. The sensor is inexpensive and can be changed in about 30 mins.
Replace rear differential speed sensor as follows:
a) Remove parking brake cable bracket (1/2" socket)
b) Remove speed sensor bolt (9/16" deep socket)
c) Remove metal speed sensor cover
d) Remove speed sensor from rear differential housing (use channel lock pliers, twist gently back and forth while applying upward pressure. Once the speed sensor has a small gap between it and the rear differential housing, insert a flat-blade screwdriver and gently apply upward pressure while gently twisting speed sensor back and forth.
e) Disconnect speed sensor from speed sensor cable
f) Lubricate new sensor with WD-40, insert into rear differential housing. It will NOT go in all the way by hand, so do NOT force it nor hit it with anything made out of metal.
g) Replace metal speed sensor cover
h) Insert speed sensor bolt and tighten LIGHTLY until a small amount of pressure is felt. Tap speed sensor with rubber hammer until it pops into housing. Finish tightening of speed sensor bolt.
i) Replace brake cable bracket, replace 1/2" nut and tighten
j) Disconnect positive battery cable for 2 minutes, reconnect positive battery cable

Please do accept the solution if the issue is resolved or else revert for further assistance.


Thanks
Rylee