Red — stop now
Brake system
Either the handbrake is on, the brake fluid has dropped below the mark, or the control unit has found a fault in the brakes.
A red lamp means you should not keep driving. Pull over, switch the engine off and sort it out there.
What to do now
- Check the obvious first: is the handbrake fully released?
- Look into the brake fluid reservoir. A dropped level means either worn pads or a leak.
- If the pedal has gone soft or sinks to the floor, do not drive at all.
- The fluid level drops without any leak: as the pads wear, it moves into the caliper pistons. So a reservoir topped up to the brim overflows as soon as new pads go in.
Codes usually behind it
The lamp only says that something is wrong. The code says what exactly — read it with an adapter and look it up here.
C0031Left front wheel speed sensor malfunctionC0037Left rear wheel speed sensor malfunctionC0061ABS hydraulic unit valve malfunction
What to read next
A lamp is not a diagnosis. The same symbol lights up for a dozen different reasons, and only the code stored in the car tells them apart.
How the app helps
CarScan reads the codes behind the lamp through an OBD-II adapter, explains them in plain words and puts them into a report you can show to a mechanic.