Brake warning light flashing on and then off frequently - Pontiac G8 Forum: G8 Forums - G8Board.com
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post #1 of 12 (permalink) Old 06-25-2018, 05:46 PM Thread Starter
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Brake warning light flashing on and then off frequently

Around every 5 minutes of driving my brake warning light will flash on and off. The brake fluid is good and full, pads and rotors are fairly new. The only effect of this is that my cruise control is disabled on the highway when it happens so I need to reset it (and the annoying ding of course). Has anyone dealt with this before?

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post #2 of 12 (permalink) Old 06-25-2018, 08:43 PM
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There are 3 things that can cause that warning to illuminate. Parking brake, low fluid level, or a problem with the electronic brake distribution circuit within the EBCM. Easy enough to eliminate the parking brake handle by verifying that the light will come on with the first click on pull up, an extinguish when moved back to full off. Also maybe due a little handle wiggling when in the full release position. This to make sure that the switch is not intermittently closing at that full handle stowed position. If OK, disconnect the low level senor connector at the master cylinder reservoir. Go for a type of drive that you know would cause that light to illuminate (as it has been doing). That connector disconnect equals a good level sensor condition. You DON'T want that third condition to be the problem. So I'll stop here to see how things panned out (if you chose to try any of this).
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post #3 of 12 (permalink) Old 06-25-2018, 09:05 PM Thread Starter
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Originally Posted by GOPHERIT View Post
There are 3 things that can cause that warning to illuminate. Parking brake, low fluid level, or a problem with the electronic brake distribution circuit within the EBCM. Easy enough to eliminate the parking brake handle by verifying that the light will come on with the first click on pull up, an extinguish when moved back to full off. Also maybe due a little handle wiggling when in the full release position. This to make sure that the switch is not intermittently closing at that full handle stowed position. If OK, disconnect the low level senor connector at the master cylinder reservoir. Go for a type of drive that you know would cause that light to illuminate (as it has been doing). That connector disconnect equals a good level sensor condition. You DON'T want that third condition to be the problem. So I'll stop here to see how things panned out (if you chose to try any of this).
Thank you so much for posting this! I verified that the light comes on when I pull the ebrake. Not sure what I need to unbolt to be able to pull the sensor from the master cylinder - the bolts seem to be in a tough to reach spot, so will go at that in the next few days and hopefully that is the problem.

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post #4 of 12 (permalink) Old 06-25-2018, 11:15 PM
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The brake fluid low level sensor is located to the lower left of the master cylinder. Simply disconnect the connector and see if the light continues to flash on and off. If the level sensor is determined to be the culprit, drain and refill the master cylinder reservoir with fresh brake fluid to see if contaminated fluid is causing the sensing mechanism(s) to "stick". Good luck

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post #5 of 12 (permalink) Old 07-06-2018, 11:10 AM Thread Starter
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The brake fluid low level sensor is located to the lower left of the master cylinder. Simply disconnect the connector and see if the light continues to flash on and off. If the level sensor is determined to be the culprit, drain and refill the master cylinder reservoir with fresh brake fluid to see if contaminated fluid is causing the sensing mechanism(s) to "stick". Good luck

I unplugged the sensor from the brake master cylinder and the brake light stayed on full time as opposed to turning off and on like before. Hmm. Apparently the sensor is integrated (not removable) from the brake master cylinder so there is no way to replace it without replacing the whole master cylinder. I'm going to try putting a paper clip in the sensor (jumper) to see if that does the trick.

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Last edited by EMax; 07-06-2018 at 01:04 PM. Reason: Added a sentence
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post #6 of 12 (permalink) Old 07-14-2018, 08:16 PM
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Two days ago, disconnected the brake fluid low level sensor on the master cylinder causing the brake light near the speedometer to illuminate, a constant chime, and a symbol with an exclamation point enclosed in a circle with parentheses on the driver's information center. Was merely trying to clarify the preceding statement and pondered its accuracy a few days after commenting. Jumping the leads in the sensor connector is a better way to test the low level sensor. Good luck

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post #7 of 12 (permalink) Old 05-06-2019, 01:34 PM
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Two days ago, disconnected the brake fluid low level sensor on the master cylinder causing the brake light near the speedometer to illuminate, a constant chime, and a symbol with an exclamation point enclosed in a circle with parentheses on the driver's information center. Was merely trying to clarify the preceding statement and pondered its accuracy a few days after commenting. Jumping the leads in the sensor connector is a better way to test the low level sensor. Good luck
I've been having the same issue as the OP. Were you ever able to resolve the problem? I tried disconnecting as Pony Man had mentioned and I got a constant chime. Additionally, I jumped the pins on the connector and still had the constant chime.

I searched on Camaro5 and some people had mentioned that it was based on resistance, OHM. I'm no electrician, but from my experience, disconnecting or jumping the connector will not get rid of the warning light.

The previous owner of the car did install an aftermarket brake fluid cap. The fluid does look a bit dirty; I'm assuming because the seal may not be as good as the OEM seal and allowed dust/dirt to get into the master cylinder. I am going to use a syringe to remove the dirty fluid, put new fluid and bleed the brake lines til they run clean. Will report back.
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post #8 of 12 (permalink) Old 05-06-2019, 01:37 PM Thread Starter
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Quote:
Originally Posted by PONY MAN View Post
Two days ago, disconnected the brake fluid low level sensor on the master cylinder causing the brake light near the speedometer to illuminate, a constant chime, and a symbol with an exclamation point enclosed in a circle with parentheses on the driver's information center. Was merely trying to clarify the preceding statement and pondered its accuracy a few days after commenting. Jumping the leads in the sensor connector is a better way to test the low level sensor. Good luck
I've been having the same issue as the OP. Were you ever able to resolve the problem? I tried disconnecting as Pony Man had mentioned and I got a constant chime. Additionally, I jumped the pins on the connector and still had the constant chime.

I searched on Camaro5 and some people had mentioned that it was based on resistance, OHM. I'm no electrician, but from my experience, disconnecting or jumping the connector will not get rid of the warning light.

The previous owner of the car did install an aftermarket brake fluid cap. The fluid does look a bit dirty; I'm assuming because the seal may not be as good as the OEM seal and allowed dust/dirt to get into the master cylinder. I am going to use a syringe to remove the dirty fluid, put new fluid and bleed the brake lines til they run clean. Will report back.
The issue with mine was a bad ground wire from the brake master cylinder. I couldnt figure it out so took it to a shop and thats what they told me, and they regrounded the master cylinder which fixed the issue. Good luck!

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post #9 of 12 (permalink) Old 05-06-2019, 03:09 PM
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The W/D shows an reads that the brake fluid level sensor is a 2 position switch (either open or closed contacts). A normal system would see that switch in an open condition at all times. If the Instrument Panel Cluster see's that the switch contacts are closed, it will turn on the red brake light in a steady state. So technically, when the low level sensor/switch connector is disconnected, it should create the same condition as telling the IPC, that the master cylinder reservoir fluid level is good (switch contacts in an open condition). Having a faulty/intermittent ground actually would assist in *preventing* the red light from coming on (very confusing). If the power wire arriving at the connector had developed a constant or intermittent short to ground, that would cause either a steady or intermittent brake light condition. Even the circuit test procedure (in the service manual) is backwards from the W/D itself. In itself, that would not make any difference to a open/closed switch. If you have a meter, check for 5 volts DC +/- a little from either pin to a good ground source. If OK, the remaining pin must have a next to zero resistance reading to a ground source. If the power wire has developed an intermittent short to ground condition, you (or somebody) might be in for a somewhat long an painful T/S session trying to zero in on it.






Added info>>>>> Reading another section in the service manual, is counter to the above statement on switch position. This is the information from that section of the service manual titled "Brake Warning Indicator Malfunction", It says that the switch is normally closed (when the fluid level is correct). That makes the fix by "EMax" seem more probable. This darn service manual is so screwed up. The ground return wire from the low level switch is joined with at least 10 or 12 other wires going to the same grounding location. It is located on the inside right frame rail approximately below the fuse an ECM modules. Think you need to gain access to that grounding location an carefully check out the condition of the grouped together wires. Its overall condition may affect one or more things attached at that location, or that particular wire is breaking down (as in open at times an connected at times).

Last edited by GOPHERIT; 05-06-2019 at 04:53 PM. Reason: added info
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post #10 of 12 (permalink) Old Today, 11:30 AM
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Is this what everyone else is seeing? Just started on my 2008 a week ago, has ~98k miles. In addition, I also see small "Brake" message in the dash that you normally see when parking brake engaged.

It was actually on the whole day at one point, but lately its only been coming on occasionally.

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post #11 of 12 (permalink) Old Today, 01:35 PM
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If memory is correct, yes when the connector to the brake fluid level sensor was disconnected. If you use the parking brake a lot to keep the weight of the vehicle off the parking prowl, then check the operation of parking brake sensor. Awhile ago, had to replace it due to the very same problem and fortunately they are relatively inexpensive (aftermarket) and easy to fix.

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post #12 of 12 (permalink) Old Today, 03:40 PM
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"drewdog" >>>>> If you know your master cylinder reservoir is full, you could run a test by disconnecting that reservoir low level switch connector. Then fashion up a wire that you would connect to pin #1 (brown/white) in color, with the other end of the wire connected to a known good ground source (like the underhood grounding jump post). That wire (coming from the instrument cluster), is looking for a constant ground condition. If the switch failed open, you'd get a constant brake light condition. If the black ground wire (in pin #2 position) is intermittent, it would then cause a *BRAKE* light on, *BRAKE* light off condition.
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