What exactly is Code C0031 and why does it happen?

Code C0031 is a diagnostic trouble code that indicates a malfunction in the left front wheel speed sensor circuit. This code is set by your vehicle’s ABS Control Module when it detects an abnormal signal, complete loss of signal, or electrical fault in the circuit connected to the left front wheel speed sensor. The sensor’s job is to monitor wheel rotation speed and send this critical data to safety systems like ABS, traction control, and electronic stability control. When the circuit fails, these essential safety systems may disable themselves to prevent unpredictable operation.

How do I know if my vehicle has Code C0031?

Key symptoms include: illuminated ABS warning light, traction control system warning, electronic stability control alert, and potentially multiple dashboard warning lights appearing simultaneously. You may notice loss of anti-lock braking function during hard stops, disabled traction control during acceleration on slippery surfaces, and compromised stability control during cornering. Your diagnostic scanner will show Code C0031 stored in the ABS module, and live data may reveal the left front sensor showing zero speed or erratic readings while other sensors display normal values.

Is this something I can fix myself, or do I need a professional?

DIY suitable if: you have basic mechanical skills, proper tools (socket set, jack, jack stands, multimeter), and understand electrical safety procedures around ABS systems. The repair typically involves sensor replacement with careful attention to mounting specifications and air gap requirements. Call a professional if: you lack experience with automotive electrical systems, don’t have proper diagnostic equipment, need complex wiring repairs, or when multiple related codes appear. Required skill level: Intermediate to advanced due to safety system involvement.

Why is my ABS light on and how serious is this problem?

The ABS light indicates your anti-lock braking system has detected a fault and may have disabled itself. This is serious because you lose critical safety features that prevent wheel lockup during emergency braking, help maintain steering control on slippery surfaces, and provide stability assistance during sudden maneuvers. Immediate risks: increased stopping distances, potential wheel lockup and skidding, loss of directional control during panic stops, and disabled traction/stability control systems. Drive carefully and repair promptly to restore full safety system functionality.

What tools do I need to diagnose and fix this problem?

Essential tools: OBD-II scanner capable of reading ABS codes, socket set (typically 10mm and 12mm), breaker bar with lug nut sockets, hydraulic jack and jack stands, multimeter for electrical testing, wire brush or sandpaper for cleaning, and penetrating oil for stuck sensors. Optional but helpful: oscilloscope for advanced signal analysis, torque wrench for proper reassembly specifications, electrical contact cleaner for connector maintenance. Safety equipment: safety glasses, work gloves, and adequate lighting for proper visibility during repairs.

What safety precautions should I take during this repair?

Critical safety steps: park on level surface with parking brake engaged, disconnect battery negative terminal and wait 10 minutes before starting work, use proper jack points and jack stands (never rely on jack alone), wear safety glasses and work gloves. Electrical safety: avoid short circuits by keeping tools away from live circuits, handle connectors carefully to prevent damage, and ensure proper grounding. Component safety: don’t force stuck sensors, clean mounting surfaces thoroughly, and torque bolts to specification to prevent damage.

What are the risks if I ignore this problem?

Immediate risks: complete loss of ABS function means wheels can lock during hard braking, potentially causing loss of steering control and longer stopping distances. Traction control disability means no automatic wheel spin prevention during acceleration on slippery surfaces. Stability control loss reduces your vehicle’s ability to maintain directional control during emergency maneuvers. Progressive damage: ignoring the problem won’t cause additional mechanical damage, but you remain vulnerable to accidents that these safety systems could help prevent.

C Codes

C codes refer to chassis-related issues within the OBD-II diagnostic system. These codes help pinpoint faults in systems such as the suspension, steering, and braking mechanisms. Although less common than P codes, C codes are critical for ensuring safe vehicle handling and stability.

Quickly look up your code using the search field in the table below:

OBD II C Codes Table with Search

DTC Number	DTC Naming	Location
C0000	ISO/SAE Reserved
C0001	TCS Control Channel "A" Valve 1 (Subfault)
C0002	TCS Control Channel "A" Valve 2 (Subfault)
C0003	TCS Control Channel "B" Valve 1 (Subfault)
C0004	TCS Control Channel "B" Valve 2 (Subfault)
C0005	ISO/SAE Reserved
C0006	ISO/SAE Reserved
C0007	ISO/SAE Reserved
C0008	ISO/SAE Reserved
C0009	ISO/SAE Reserved
C000A	ISO/SAE Reserved
C000B	ISO/SAE Reserved
C000C	ISO/SAE Reserved
C000D	ISO/SAE Reserved
C000E	ISO/SAE Reserved
C000F	ISO/SAE Reserved
C0010	Left Front Inlet Control (Subfault)
C0011	Left Front Outlet Control (Subfault)
C0012	Left Front Hydraulic Release Too Long (Subfault)
C0013	ISO/SAE Reserved
C0014	Right Front Inlet Control (Subfault)
C0015	Right Front Outlet Control (Subfault)
C0016	Right Front Hydraulic Release Too Long (Subfault)
C0017	ISO/SAE Reserved
C0018	Left Rear Inlet Control (Subfault)
C0019	Left Rear Outlet Control (Subfault)
C001A	Left Rear Hydraulic Release Too Long (Subfault)
C001B	ISO/SAE Reserved
C001C	Right Rear Inlet Control (Subfault)
C001D	Right Rear Outlet Control (Subfault)
C001E	Right Rear Hydraulic Release Too Long (Subfault)
C001F	ISO/SAE Reserved
C0020	ABS Pump Motor Control (Subfault)
C0021	Brake Booster Performance (Subfault)
C0022	Brake Booster Solenoid (Subfault)
C0023	Stop Lamp Control (Subfault)
C0024	ISO/SAE Reserved
C0025	ISO/SAE Reserved
C002E	ISO/SAE Reserved
C002F	ISO/SAE Reserved
C0030	Left Front Tone Wheel (Subfault)
C0031	Left Front Wheel Speed Sensor (Subfault)
C0032	Left Front Wheel Speed Sensor Supply (Subfault)
C0033	Right Front Tone Wheel (Subfault)
C0034	Right Front Wheel Speed Sensor (Subfault)
C0035	Right Front Wheel Speed Sensor Supply (Subfault)
C0036	Left Rear Tone Wheel (Subfault)
C0037	Left Rear Wheel Speed Sensor (Subfault)
C0038	Left Rear Wheel Speed Sensor Supply (Subfault)
C0039	Right Rear Tone Wheel (Subfault)
C003A	Right Rear Wheel Speed Sensor (Subfault)
C003B	Right Rear Wheel Speed Sensor Supply (Subfault)
C003C	Rear Tone Wheel (Subfault)
C003D	Rear Wheel Speed Sensor (Subfault)
C003E	Rear Wheel Speed Sensor Supply (Subfault)
C003F	ISO/SAE Reserved
C0040	Brake Pedal Switch "A" (Subfault)
C0041	Brake Pedal Switch "B" (Subfault)
C0042	Brake Pedal Position Sensor "Circuit A" (Subfault)
C0043	Brake Pedal Position Sensor "Circuit B" (Subfault)
C0044	Brake Pressure Sensor "A" (Subfault)
C0045	Brake Pressure Sensor "B" (Subfault)
C0046	Brake Pressure Sensor "A"/"B" (Subfault)
C0047	Brake Booster Pressure Sensor (Subfault)
C0048	Brake Booster Travel Sensor (Subfault)
C0049	Brake Fluid (Subfault)
C004A	Brake Lining Wear Sensor (Subfault)
C004B	ISO/SAE Reserved
C004C	ISO/SAE Reserved
C004D	ISO/SAE Reserved
C004E	ISO/SAE Reserved
C004F	ISO/SAE Reserved
C0050	ISO/SAE Reserved
C0051	Steering Wheel Position Sensor (Subfault)
C0052	Steering Wheel Position Sensor "Signal A" (Subfault)
C0053	Steering Wheel Position Sensor "Signal B" (Subfault)
C0054	Steering Wheel Position Sensor "Signal C" (Subfault)
C0055	Steering Wheel Position Sensor "Signal D" (Subfault)
C0056	ISO/SAE Reserved
C0057	ISO/SAE Reserved
C0058	ISO/SAE Reserved
C0059	ISO/SAE Reserved
C005A	ISO/SAE Reserved
C005B	ISO/SAE Reserved
C005C	ISO/SAE Reserved
C005D	ISO/SAE Reserved
C005E	ISO/SAE Reserved
C005F	ISO/SAE Reserved
C0060	ISO/SAE Reserved
C0061	Lateral Acceleration Sensor (Subfault)
C0062	Longitudinal Acceleration Sensor (Subfault)
C0063	Yaw Rate Sensor (Subfault)
C0064	Roll Rate Sensor
C0065	ISO/SAE Reserved
C0066	ISO/SAE Reserved
C0067	ISO/SAE Reserved
C0068	ISO/SAE Reserved
C0069	Yaw Rate/Longitude Sensors (Subfault)
C006A	Multi-axis Acceleration Sensor (Subfault)
C006B	Stability System Active Too Long (Subfault)
C006C	Stability System
C006D	ISO/SAE Reserved
C006E	ISO/SAE Reserved
C006F	ISO/SAE Reserved
C0070	ISO/SAE Reserved
C0071	2/4 Wheel Drive Status Input (Subfault)
C0072	Brake Temperature Too High (Subfault)
C0073	Delivered Driving Torque (Subfault)
C0074	Requested Driving Torque (Subfault)
C0075	Extended Brake Pedal Travel, output to PCM (Subfault)
C0076	PWM for Traction Control (Subfault)
C0077	Low Tire Pressure (Subfault)
C0078	Tire Diameter (Subfault)
C0079	Variable Effort Steering (Subfault)
C007A	ISO/SAE Reserved
C007B	ISO/SAE Reserved
C007C	ISO/SAE Reserved
C007D	ISO/SAE Reserved
C007E	ISO/SAE Reserved
C007F	ISO/SAE Reserved
C0080	ISO/SAE Reserved
C0081	ABS Malfunction Indicator (Subfault)
C0082	Brake System Malfunction Indicator (Subfault)
C0083	Tire Pressure Monitor Malfunction Indicator (Subfault)
C0084	Traction Active Indicator (Subfault)
C0085	Traction Disable Indicator (Subfault)
C0086	Vehicle Dynamics Indicator (Subfault)
C0087	ISO/SAE Reserved
C0088	ISO/SAE Reserved
C0089	TCS Disable Switch (Subfault)
C008A	TCS Mode Control (Subfault)
C008B – C0FFF	ISO/SAE Reserved
C1000	Manufacturer Controlled DTC
C2000	Manufacturer Controlled DTC
C3000	ISO/SAE Reserved
Code not found