Chassis, generic

C0502 Left Front Wheel Speed Sensor A Circuit Low

Check engine lightOn

EmissionsNot relevant

Drive cycleNot required

Limp modePossible

C0502 reports the left front sensor circuit below its valid level, mostly a grounded wire or a supply that has sagged. In GM's 2019 tables (19OBDG03D) the brake module's Polaris ASIC sets C0502 for three conditions: the low side shorted to ground, tested only at power-up or after clearing codes (100 ms); sensor undervoltage (20 ms); and, unusually, an open sensor drawing under 3.5 mA, which other GM tables file as C0500. All are Type A. Audi bulletin 2061331/1 for 2017–2021 A4, A5, S and RS models stores C050200 as short to ground: a wire was poorly crimped in the front sensor connector, and the remedy is a new speed sensor and pad-wear harness. Mitsubishi's C1061-11 covers short and open circuits and even lights the parking brake warning.

Likely causes

Sensor wire chafed through to ground or poorly crimped in the connector

Sensor supply voltage too low (battery, fuse or module output)

Internal short in the left front sensor

Symptoms

ABS and ESC lamps on right after starting
Parking brake warning or electric parking brake functions restricted on some models

Repair estimate

DifficultyMediumDIY possible

Parts and labour€30–450

Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

wss lfsensor wiring

References: gsi.ext.gm.com, static.nhtsa.gov, mitsubishitechinfo.com.