C0045 — Left Rear Wheel Speed Sensor Circuit

Quick answer

• What the C0045 code means: The vehicle's computer has detected an electrical fault in the circuit connected to the left rear wheel speed sensor.
• Severity: Get it diagnosed soon, but it's generally safe to drive carefully for a short period unless the ABS warning light is on and braking performance is noticeably affected.
• Most common cause: A damaged or corroded left rear wheel speed sensor or its wiring.

What the C0045 code means

The official OBD-II definition for C0045 is "Left Rear Wheel Speed Sensor Circuit." In simpler terms, this code indicates that there's an issue with the electrical circuit responsible for transmitting data from the left rear wheel speed sensor to the Anti-lock Braking System (ABS) control module and other vehicle systems. The wheel speed sensor monitors the rotation of the wheel and sends this information to the car's computer. This data is crucial for the ABS, traction control, stability control, and sometimes even the transmission, speedometer, and cruise control systems to function correctly. When the circuit has an open, short, or an intermittent signal, the C0045 code is triggered.

Common symptoms

• Illuminated ABS warning light on the dashboard.
• Illuminated traction control light on the dashboard.
• Loss of ABS functionality.
• Loss of traction control functionality.
• Inconsistent speedometer readings (rare, but possible if the rear wheel speed sensor also feeds the speedometer).
• Harsh or erratic transmission shifting (in some vehicles where wheel speed data is used for transmission control).
• Loss of cruise control functionality.
• Brake pedal pulsation when braking (if ABS is misfiring due to faulty data).

Common causes

1. Damaged or faulty left rear wheel speed sensor: This is the most frequent culprit. The sensor can be damaged by debris, corrosion, or simply fail due to age and wear.
2. Damaged or corroded wiring/connector: The wires leading to and from the left rear wheel speed sensor can be frayed, cut, or corroded, interrupting the electrical signal. The connector itself can also become corroded or loose.
3. Worn or damaged wheel bearing (with integrated sensor): Some wheel bearings have the wheel speed sensor integrated into them (often a magnetic encoder ring). If the bearing is failing, it can damage the sensor or disrupt its signal.
4. Tone ring/ABS reluctor ring damage: The tone ring is a toothed ring that the wheel speed sensor reads. If it