C0509Right Front Wheel Speed Sensor A Circuit High
- Generic OBD-II code · Chassis
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- C0509 means the right front sensor line carries more current or voltage than allowed. GM's 2019 tables (19OBDG03D) set it within 100 ms when the high-side current passes 40 mA, or when the Polaris ASIC reports either sensor line shorted to battery or an overcurrent on the low side; it is Type A. That limit sits well above anything a working sensor consumes, so a stuck reading there is a wiring or sensor fault, not a speed signal. Bosch describes its active sensors as working with a two-wire interface that follows an international standard and signals by current; there the brake module feeds the sensor and reads its pulses over the same pair, so one chafed spot affects both supply and signal. Mitsubishi assigns C1063-12, a short in the front right circuit, detected within 1 s and with MIL after one trip.
- What you may notice
- ABS and ESC lamps on immediately, check-engine lamp on some makes
- ABS, EBD and hill start assist suspended
- Likely causes
- LikelySensor line chafed against a battery-voltage wire
- PossibleRight front sensor drawing excess current due to an internal short
- RareSensor supply driver in the ABS module defective
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.