C0027 Code – ABS Rear Left Wheel Speed Sensor Circuit Fault

The C0027 Diagnostic Trouble Code (DTC) is a manufacturer-specific chassis code related to the Anti-lock Braking System (ABS). On many Subaru models, it indicates a Rear Left ABS Wheel Speed Sensor Circuit Open or Short. Other manufacturers may use this code for different wheel speed sensor faults or ABS circuit problems. 0

Common Symptoms

• ABS warning light ON.
• Traction Control (TCS) or Stability Control (ESC/VDC) disabled.
• Brake warning light illuminated.
• ABS system becomes inoperative.

Possible Causes

• Faulty rear left ABS wheel speed sensor.
• Open or short circuit in the sensor wiring.
• Corroded or loose electrical connector.
• Damaged tone ring (reluctor ring).
• Faulty wheel bearing affecting sensor signal.
• ABS control module malfunction.

How to Diagnose

1. Scan the ABS module for stored DTCs.
2. View Live Data and compare all four wheel speed sensors.
3. Inspect the rear left sensor wiring and connector.
4. Check the tone ring for cracks, rust, or missing teeth.
5. Measure sensor resistance and AC output while rotating the wheel.
6. Repair the fault, clear the code, and perform a road test.

C0027 Code Meaning by Vehicle Brand

Vehicle Brand	Typical Meaning
Subaru	Rear Left ABS Wheel Speed Sensor Circuit Open or Short.
GM (Chevrolet, GMC, Cadillac, Buick)	Left Front or Left Rear Wheel Speed Sensor Signal Fault (varies by model and year).
Chrysler / Dodge / Jeep / RAM	Manufacturer-specific ABS system fault.
Toyota / Lexus	Manufacturer-specific ABS sensor or actuator fault.
Ford / Lincoln	Manufacturer-specific ABS diagnostic code.
Honda / Acura	Manufacturer-specific ABS system fault.
Hyundai / Kia	Manufacturer-specific brake control system fault.
Volkswagen / Audi / Skoda / SEAT	Manufacturer-specific ABS electronics fault.

Related DTCs

• C0025
• C0026
• C0028
• C0035
• C0040

Important: The meaning of C0027 varies by manufacturer. Subaru commonly defines it as a Rear Left ABS Wheel Speed Sensor Circuit Open or Short, while other brands may assign a different ABS-related definition. Always verify the vehicle-specific service information before replacing parts.