((Brake)) light on

[Chooch]

They are a now GMC but was a former GMC/Pontiac dealer. The GM Tech's there I trust. Usually when I bring it in, they let me in the bay, commented on the mods being well done. let me watch. They use the GM scan tools. That is why they are in a way perpelxed, they saw the brake check light come on.

They will find it, just time, they are good. And I do not trust many to work on my car. These guys I do

Was this tech at the dealer and what scan tool did they use? The GM Tech 2 or Tech2Win may be the only device to accurately diagnose. Even the fanciest of generic scan tools will not diagnose beyond the standard SAE powertrain codes.

[jkaetz]

Was this tech at the dealer and what scan tool did they use? The GM Tech 2 or Tech2Win may be the only device to accurately diagnose. Even the fanciest of generic scan tools will not diagnose beyond the standard SAE powertrain codes.

There are now tools that will scan the rest of the modules as well. I have one that will let me communicate with nearly every module, powertrain, transmission, abs, steering, radio, hvac, etc... and see the data in real time. In my G6 convertible it will read all the convertible top data out as well. I was pleasantly surprised with its ability to communicate with more than simply the powertrain.

https://www.amazon.com/DiagLink-Read...words=diaglink

You get the first manufacturer of your selection for free, other manufacturers are $10 each. And yes, GM covers ALL GM vehicles, no divisions between brands.

[Sheffield Steve]

There was a recall on the G8 for this very issue. Not sure if it's relevent to you though.

Vehicle Make / Model: Model Year(s): PONTIAC / G8 2008-2009
Manufacturer: GENERAL MOTORS CORP.
Mfr's Report Date: MAY 20, 2009
NHTSA CAMPAIGN ID Number: 09V172000 N/A
NHTSA Action Number: N/A
Component: TIRES:PRESSURE MONITORING AND REGULATING SYSTEMS
Potential Number of Units Affected: 35038
Summary:
GM IS RECALLING 35,038 MY 2008-2009 PONTIAC G8 VEHICLES FOR FAILING TO COMPLY WITH THE REQUIREMENTS OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 108, "LAMPS, REFLECTIVE DEVICES, AND ASSOCIATED EQUIPMENT" AND FEDERAL MOTOR VEHICLES SAFETY STANDARD NO. 138, "TIRE PRESSURE MONITORING SYSTEMS". THE BRAKE PEDAL POSITION SWITCH MAY HAVE BEEN INCORRECTLY PROGRAMMED. WITH THIS CONDITION, THE BRAKE LAMPS MAY BE CONTINUALLY ILLUMINATED AND FAIL TO WARN A FOLLOWING DRIVER WHEN THE VEHICLE IS BRAKING. ALSO CERTAIN VEHICLES MAY HAVE INCORRECT VALUES PROGRAMMED INTO THE TIRE PRESSURE MONITORING SYSTEM THAT WILL NOT ILLUMINATE THE LOW TIRE PRESSURE TELLTALE UNTIL TIRE PRESSURE FALLS BELOW VALUES REQUIRED BY THE STANDARD. Consequence:
INAPPROPRIATE, NON-STANDARD LIGHTS COULD INCREASE THE RISK OF A CRASH OR DRIVING ON A SIGNIFICANTLY UNDER-INFLATED TIRE CAUSES THE TIRE TO OVERHEAT AND CAN LEAD TO TIRE FAILURE. Remedy:
DEALERS WILL REPROGRAM THE BRAKE POSITION SENSOR AND THE REMOTE CONTROL DOOR LOCK RECEIVER WITH THE CORRECT VALUES FREE OF CHARGE. THE RECALL IS EXPECTED TO BEGIN ON OR BEFORE JUNE 5, 2009. OWNERS MAY CONTACT GM PONTIAC AT 1-800-620-7668. Notes:
GM RECALL NO. 09101 & 09046. OWNERS MAY ALSO CONTACT THE NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION'S VEHICLE SAFETY HOTLINE AT 1-888-327-4236 (TTY 1-800-424-9153), OR GO TO HTTP://WWW.SAFERCAR.GOV .

[Napalm]

I'd put money on the fluid switch from the last report.

[cdnbiker]

I had a brake warning light issue that was very hard to diagnose. My mechanic replaced the fluid reservoir (I had to buy a complete master cylinder assembly) because the usual problem is the brake fluid level sensor in the reservoir. That did not fix it. He took the car to a GM dealer. No luck finding out the problem. My mechanic then speculated that the only thing it could be was a problem in the cluster. So he took the car to an electrical shop who replaced the cluster and that fixed the problem.

[TimothyThure]

Just been out for a while and noticed under heavy braking that the brake light appeared to come on. At least I think it was the brake light, it flashed for a second or so then disappeared.

Is this normal/known ?

[-Ray-]

A brake light should never be considered normal. It's an indication that something is wrong. My first guess is brake fluid is low. The second would be the brake light switch.