Hallo,
my 03 Tahoe started showing the red Brake Warning light. But it doesn´t come up with full brightness (like it does when I just turned the Ignition on). The Warning Light only illuminates a little bit. When I apply the parking Brake it illuminates full, after release of parking brake it is slightly on again. After removing the Battery Power for a minute the light seems to be reset and it stays normal for about 1 week. Does anybody have an Idea what tis means ?

Check brake fluid level. Top off to full mark if low.
I think there is a low fluid level switch on bottom or underside of master cylinder.
For a test on switch unplug it but do not drive it with it unplugged.
MT

Thanks for the help. I checked the reservoir and it is at the FULL Mark. When I remove the electrical connector under the Master Cylinder nothing changes. I just wonder why the Warning Light is illuminating with a very low intensity. I assume this Light is either ON or OFF completely but not somewhere between ? Or am I wrong ?

Thanks for the help. I checked the reservoir and it is at the FULL Mark. When I remove the electrical connector under the Master Cylinder nothing changes. I just wonder why the Warning Light is illuminating with a very low intensity. I assume this Light is either ON or OFF completely but not somewhere between ? Or am I wrong ?

They have several britness to them.
Depending on what is tripping it.
A emg brake switch test is to step on emg brake and if light gets brighter the emg brake light switch is working.
You might try unpluging you abs control unit to clear codes or pulling fuse.
Also check for any abs codes or brake light switch codes.
Good luck
MT

Just an Update: It turned out to the Instrument Cluster had a failure. I got a new one from the dealer and the Brake light stayed off (Certainly it comes on when ignition is on and during apply of Parking Brake). So my brakes are OK.

Thanks for posting back the fix and how it went.
Glad you got it figured out.
Did the dealer tie on any on it?
MT