C0045 – Left Rear Wheel Speed Sensor Circuit

What does C0045 mean?

The left rear wheel speed sensor circuit is malfunctioning. Rear wheel speed sensors feed the same ABS and stability control systems as the front sensors, and on many vehicles also contribute to transmission and traction control decisions.

What causes C0045?

Listed from most to least common:

1. 1Corroded connector — rear sensors sit in an exposed underbody location
2. 2Damaged wiring from road debris or salt
3. 3Failed wheel speed sensor
4. 4Debris on the sensor tip
5. 5Damaged tone ring
6. 6Wheel bearing wear affecting sensor gap

Code breakdown

Common symptoms

• ABS and traction control warning lights on
• Stability control disabled
• Possible transmission shifting differences on some vehicles
• Normal braking retained

How to diagnose

1. 1Inspect the connector for corrosion — this is the leading cause on rear sensors, especially in regions that salt roads.
2. 2Check wiring along the underbody for damage.
3. 3Remove and inspect the sensor tip for debris.
4. 4Compare wheel speed readings across all four wheels in live data.
5. 5Measure sensor resistance.
6. 6Inspect the tone ring for rust damage, which is more common at the rear.

ABS and stability control are typically disabled while this code is active. Base braking is unaffected.

Common fixes and estimated costs

Costs are rough US estimates including parts and labor. Actual pricing varies significantly by vehicle, region, and shop rates.

Good to know

Rear sensors suffer far more corrosion damage than front ones because of their exposed position. Cleaning and dielectric grease on a corroded connector sometimes resolves the fault entirely.

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