# Brake light on dash comes on.....



## JRT (Jan 17, 2011)

2002gmc sierra 2500hd 4x4. While driving the parking brake light will occasionally turn on. Master Cylinder is full and not leaking. Replaced sensor in master Cylinder. Parking pedal is not engaged.. It will come on at random times. What could be the issue?


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## Brian Young (Aug 13, 2005)

Look under the dash at the brake pedal and see if there is a brake light switch near the top of the pedal.


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## theholycow (Nov 29, 2002)

If the parking brake is not adjusted properly, I imagine the parking brake pedal can sink just enough to trigger the light. Did you try pulling the pedal up, or merely operating the brake release (thereby depending on tension in the system to pull the pedal up)?

It's supposed to go "Ding!" if it detects that the parking brake is engaged while you're driving, but I'm not sure if it only does that if you start driving from a stop, or if it does it any time the brake is engaged while driving. Let's assume, for diagnostic purposes, the former. Is the light ever on immediately after starting the truck with the brake disengaged? If so, when you start driving does it go "Ding!"?


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## theholycow (Nov 29, 2002)

Ah, found it. Here's the "Brake Warning Indicator Always On" troubleshooting chart from the GM OEM service manual.
http://www.justanswer.com/chevy/1kheb-park-brake-warning-light-2nd-time-truck-started.html
It is rather dependent on a scan tool that can pull brake codes, but there's still useful stuff in there that you can try without such a tool.


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## JRT (Jan 17, 2011)

The light is not on when the truck is started. It comes on while driving. That's why I don't think it's the parking pedal. When the light comes on it makes no noise, no ding. I always make sure the parking brake pedal is up by pulling up with my hand. While holding the parking brake release. I did notice some brake fluid dripping down from the upper rod on the brake pedal. I have a new parking brake switch to replace but need time to remove and replace it. I'm beginning to wonder if there may be a wiring problem as the truck has 310,000kms on it. But it is perfect other than that... I'm gonna review the notes from gm now that was posted above. I have a obd2reader but it won't read the brake system.
input greatly appreciated..Thumbs UpThumbs Up


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## theholycow (Nov 29, 2002)

Brake fluid dripping down the pedal sounds like a Bad Thing.


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## JRT (Jan 17, 2011)

I think it's the power steering fluid leaking from the pedal assembly as both systems are tied together. It's a leaky seal. I'm going to replace the booster this spring. I am trying to hunt down a code reader for the brake system. That will be my best bet I think.


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## leolkfrm (Mar 11, 2010)

forget teh code reader...have it put on a scanner...gives more information and more accurate info


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