C5 Corvette - Brake Warning Light On
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2nd Gear
Joined: Feb 2024
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C5 Corvette - Brake Warning Light On
I purchased my C5 about 6 months ago, one of my dream cars my whole life. Since I bought it, it's had the brake warning light on on the instrument panel as well as displaying "LOW BRAKE FLUID" on the dash, despite the reservoir being filled past the maximum line. The previous owner tried to remedy this by changing out the master with an OEM AC Delco unit and flushing the system, done by a shop. Last weekend I flushed the system myself and instead had the system filled to right at the maximum line, no change. I checked the ground to the connector and it was good. I replaced the sensor with another OE GM unit just in case the one that came with the master was defective. Still no change. I even pulled the sensor out of the reservoir to see if maybe the float was stuck on the bottom of the reservoir and still no change. I've put about 50 miles on it since. I'm at a bit of a loss, per a wiring diagram I saw, the light is on with a closed circuit, so a break in the wires or fuse would make the light go off, right? Do I have to clear the code off the PCM? Is there a way to disable the brake monitoring system entirely? I should mention my car has a big cam and a tune, I don't think this would effect this. Any insight is greatly appreciated.
Pro
Joined: Aug 2010
Posts: 622
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From: Montgomery Texas
The previous owner replaced the master cylinder in order to fix the low fluid warning lamp?!?!?!
The low fluid level sensor provides a ground to the warning light, via ground 113. If the warning light is illuminated all of the time, regardless of the float position of the level switch, then the warning lamp is being supplied with an alternative ground.
But, before you get too deep into that circuit, notice that within the IP, there is a splice that allows the brake warning lamp to do double duty for both the fluid level input as well as the hand brake input (see attached).
The low fluid level sensor provides a ground to the warning light, via ground 113. If the warning light is illuminated all of the time, regardless of the float position of the level switch, then the warning lamp is being supplied with an alternative ground.
But, before you get too deep into that circuit, notice that within the IP, there is a splice that allows the brake warning lamp to do double duty for both the fluid level input as well as the hand brake input (see attached).
Melting Slicks
Joined: Nov 2014
Posts: 3,399
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From: Havre de Grace Maryland
Welcome to CF and the C5 electrical anomolies. Just a thought like when our computers do stupid things and a reboot fixes, try disconnecting the battery for a few minutes. Maybe a reboot will fix it.
Thread Starter
2nd Gear
Joined: Feb 2024
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Yes, they replaced the master cylinder. I don't think they knew what they were doing because they also replaced an airbag resistor to mitigate an airbag warning light that is obviously due to the fact that the car has an aftermarket steering wheel with no airbag.
On my IPC I'm getting a message displaying "Low Brake Fluid" as well as the warning light which is what lead me to believe it didn't have anything to do with the parking brake. Is this an incorrect assumption?
I tested continuity between the sensor connector and ground 113 and I had continuity. So the wire must be shorting somewhere on it's way to the IPC, correct? Where do you guys get all of these diagrams? I bought a Haynes manual and it barely has anything useful. Thanks a lot for your help.
On my IPC I'm getting a message displaying "Low Brake Fluid" as well as the warning light which is what lead me to believe it didn't have anything to do with the parking brake. Is this an incorrect assumption?
I tested continuity between the sensor connector and ground 113 and I had continuity. So the wire must be shorting somewhere on it's way to the IPC, correct? Where do you guys get all of these diagrams? I bought a Haynes manual and it barely has anything useful. Thanks a lot for your help.
Pro
Joined: Aug 2010
Posts: 622
Likes: 169
From: Montgomery Texas
Yes, they replaced the master cylinder. I don't think they knew what they were doing because they also replaced an airbag resistor to mitigate an airbag warning light that is obviously due to the fact that the car has an aftermarket steering wheel with no airbag.
On my IPC I'm getting a message displaying "Low Brake Fluid" as well as the warning light which is what lead me to believe it didn't have anything to do with the parking brake. Is this an incorrect assumption?
I tested continuity between the sensor connector and ground 113 and I had continuity. So the wire must be shorting somewhere on it's way to the IPC, correct? Where do you guys get all of these diagrams? I bought a Haynes manual and it barely has anything useful. Thanks a lot for your help.
On my IPC I'm getting a message displaying "Low Brake Fluid" as well as the warning light which is what lead me to believe it didn't have anything to do with the parking brake. Is this an incorrect assumption?
I tested continuity between the sensor connector and ground 113 and I had continuity. So the wire must be shorting somewhere on it's way to the IPC, correct? Where do you guys get all of these diagrams? I bought a Haynes manual and it barely has anything useful. Thanks a lot for your help.
The circuit, as drawn, would not permit the IPC to differentiate between a low brake fluid level situation and a parking brake situation. While it is possible that the circuit is incorrectly drawn, it would take far less time to check the hand brake lever switch than to track down issues with the schematic.
And yes, the warning light is getting a ground from somewhere, so if it's not via the level sensor, it must be via the hand brake switch. Failing that, one of the wires in the aforementioned circuits is most likely pinched somewhere.
Melting Slicks
Joined: Sep 2021
Posts: 2,555
Likes: 1,213
I bought a physical copy for my 2000.
The electronic versions are better than nothing and they have data from multiple years. I find them rather difficult to use compared to my books.
Note that the diagram I posted is from a 2000 manual, yours may be different. But I'm happy to look around if you need something different.
The electronic versions are better than nothing and they have data from multiple years. I find them rather difficult to use compared to my books.
Note that the diagram I posted is from a 2000 manual, yours may be different. But I'm happy to look around if you need something different.
