Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Brake Fluid Level Warning Switch
A fluid level switch is incorporated into the reservoir cap.
- With sufficient fluid level the reed contact is closed
- When level drops below allowable limits, switch opens.
Since the normal position is closed, this circuit is monitored for shorts to + and ground.
The ABS ECU monitors the fluid level and issues a low fluid level message on the CAN.
The LCM receives the message and illuminates the warning lamp and generates the low brake fluid message for the message center. If the ground signal is momentary, the LCM signals the Instrument cluster of the condition. The instrument cluster then informs the ABS ECU over the CAN bus. If the signal is received prior to the activation of the pre-charge pump, the pre-charge pump activation is delayed.
If the signal is present for more then 25 seconds, the LCM issues two I BUS messages for the Instrument Cluster:
- Post "Brake Fluid Level "in the Message center
- Notify the ABS via CAN that the Fluid level has been low for more than 25 seconds.
The ABS ECU immediately switches DSC functions off and continuously illuminates the DSC indicator in the cluster.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.