C1A10 — Left Rear Wheel Speed Sensor Circuit — Open/Short

Causes

• Broken or chafed wiring in the left rear wheel sensor harness
• Corroded, loose, or damaged sensor connector/terminal
• Failed left rear wheel speed sensor (passive or active sensor)
• Short to ground or short to battery voltage in the signal/return wire
• Poor ground or lost reference supply at sensor
• Intermittent fault from wheel bearing damage or foreign debris affecting sensor air gap

Symptoms

• ABS warning lamp ON and/or traction/stability control lamp ON
• Loss of ABS/traction control functions for the affected wheel (may disable system or enter limp safety mode)
• Inconsistent or missing wheel speed reading for left rear in scan-tool live-data
• Unusual behavior during braking or stability events (reduced anti-lock function)
• Possible sporadic stability/traction interventions or illuminated multiple related fault lamps

What to check

• Read and record ABS/ESC codes and freeze frame using a diagnostic scanner
• Visually inspect left rear sensor, wiring, and connector for damage, corrosion, or contamination
• Check for bent pins, water intrusion, or corrosion in the sensor connector and ABS module connector
• Backprobe the sensor connector with ignition ON (or as the manufacturer specifies) to verify reference voltage, ground, and signal presence
• Measure sensor resistance with the connector unplugged — compare to manufacturer spec (open = infinite; short = near 0 Ω)
• Check for continuity and shorts between the sensor signal wire and chassis ground and between signal wire and battery + with multimeter

Signal parameters

• Passive (magnetic) sensor: typical DC resistance often in the hundreds to low thousands of ohms (vehicle-dependent). Open = infinite Ω; short ≈ 0 Ω.
• Passive sensor output: AC voltage proportional to wheel speed; small mV at low speed up to several volts at higher speed. No AC = open or failed sensor.
• Active (Hall/3‑wire) sensor: reference supply typically 5 V (or vehicle-specific 5–12 V), ground, and signal output. Signal usually a square wave 0–5 V (or 0–Vsupply) with frequency proportional to wheel speed.
• Short to battery: presence of battery voltage on the signal pin (≈ 12 V with ignition on) indicates short to B+.
• Short to ground: signal pin near 0 V with ignition on indicates short to ground.
• Exact resistance/voltage values are vehicle-specific; consult manufacturer specs for precise thresholds.

Similar codes