An illuminated brake hydraulic system red warning light means that there is a problem with the brake hydraulic system. If the light is intermittent and seems to come on and off depending on whether the vehicle is turning, it may mean that the brake fluid level is getting low. If the brake hydraulic system red warning light comes on and stays on, this indicates that there is a persistent problematic issue with the brake hydraulic system. The warning light can come on when a change in system hydraulic pressure is detected.
The Bulb Check: Brake Hydraulic System Warning Light
When the ignition key is rotated through the phases of Off, Run, Start, a brake systems bulb check is activated. Both the brake hydraulic systems red light and the parking brake light will illuminate. If there are no problems detected in the brake hydraulic system, the red light will go out after 1 to 2 seconds. If there is a problem detected, then the red light will stay on. The parking brake light will stay on until the parking brake is completely released. On some vehicles, these lights look very similar, so make sure you know where each light is located in the instrument panel and what its purpose is.
It is always a good idea to check your vehicle owner's manual and familiarize yourself with your vehicle's warning lights. Not all vehicles are equipped with this particular warning light.
What to Do: Brake Hydraulic System Warning Light
If the red brake light blinks, or comes on and off intermittently, and there is no change in the feel of the brake pedal, then have the vehicle properly diagnosed by a qualified repair shop as soon as possible. A complete inspection of the brake system should be performed, even if it is discovered that the light was illuminating due to a low brake fluid level. The cause of the brake fluid loss must be thoroughly determined. All sections and components of the brake hydraulic system should be verified for integrity. A properly maintained brake system should not set a red light even if the brake pads or shoes are worn to the replacement point.
If the red brake light remains illuminated, it means that there is a persistent problem in the brake system. When this occurs, the vehicle should not be driven. The vehicle needs to be towed to a qualified repair shop where it can be properly diagnosed and inspected. If the red brake light comes on while driving and stays illuminated, the vehicle should be pulled to the side of the road and towed to a qualified repair shop.
On some vehicles, the anti-lock brake system (ABS) uses some of the service brake hydraulic components to operate. If the yellow ABS light comes on and the red brake light comes on a bit later, this means the service brake system uses some of the ABS components in order to operate.
In all cases, if the red brake light comes on and stays on, there is a serious problem in the brake hydraulics system. Do not drive the vehicle; instead, have it towed immediately.