OBD-II trouble code
C0045: Left Rear Wheel Speed Sensor Circuit
The ABS module detected a fault in the left rear wheel speed sensor or its circuit. The ABS and traction/stability warning lights typically come on and those systems are disabled, but normal (base) braking still works.
Quick facts
- System
- Chassis
- Category
- ABS / Wheel Speed
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $400
- DIY difficulty
- Intermediate DIY
What does C0045 mean?
Each wheel has a speed sensor that reports how fast that wheel is turning to the anti-lock brake system (ABS) module. The module compares all four wheel speeds to detect a wheel about to lock under braking (ABS), a wheel that is spinning (traction control), or a vehicle that is sliding (stability control). C0045 sets when the module sees a fault in the left rear wheel speed sensor circuit — the signal is missing, out of range, erratic, or electrically shorted or open — so it can no longer trust that wheel's speed reading.
Because the safety systems need a reliable speed signal from every wheel, losing one input causes the module to disable ABS, traction control, and stability control and turn on the associated dash warning lights. Your ordinary hydraulic brakes are not affected — the car stops normally — but the anti-lock and traction/stability functions that help in a hard stop or on slippery roads are switched off until the fault is repaired. On vehicles with electronic parking brakes or hill-hold, a rear wheel-speed fault can occasionally disable those convenience features too.
The most common causes are a failed wheel speed sensor and damage at the sensor's exposed location. Rear sensors run along the underbody and through the rear suspension, where they are exposed to road spray, salt, and debris, so corroded or broken connectors and chafed wiring are frequent culprits; the harness routing over the rear axle is a common spot for chafing. A damaged or contaminated tone ring (the toothed reluctor the sensor reads) can also produce an erratic signal that mimics a bad sensor. Note that C0045 is the SAE-generic designation for the left rear wheel speed sensor circuit; some manufacturers — General Motors in particular — assign wheel-speed faults to different C-code numbers or use C0045 with a sub-code, so always confirm the exact definition against service data for your specific vehicle before replacing parts.
Common causes
- Failed left rear wheel speed sensor
- Corroded, broken, or loose connector at the sensor
- Chafed, cut, or open wiring in the rear harness (road/salt exposure, axle routing)
- Damaged, cracked, or contaminated tone/reluctor ring
- Excessive air gap from a loose sensor or hub/bearing play
- ABS module fault (less common)
Symptoms
- ABS warning light on
- Traction control and stability control (ESC) warning lights on
- ABS, traction, and stability features disabled
- Normal (base) braking still works
- Possible loss of hill-hold or electronic parking brake features on some vehicles
Diagnostic steps
- 1.Scan the ABS module and record all C-codes and any sub-codes to confirm which wheel and what type of fault (low/open, erratic).
- 2.Inspect the left rear wheel speed sensor, its connector, and the harness routing over the rear axle for corrosion, chafing, or damage.
- 3.Check the tone/reluctor ring for cracks, missing teeth, rust, or debris packed into the teeth.
- 4.Measure the sensor's resistance or output and compare wheel-speed live data across all four wheels while turning the wheel.
- 5.Verify the sensor air gap and that the sensor is seated properly with no hub-bearing play.
- 6.Repair or replace the sensor or wiring, clear the codes, and road-test to confirm all four wheel-speed signals track correctly.
Repair cost
$100 – $400
A wheel speed sensor is a common, moderate-cost repair: parts often run $30-$150 with about an hour of labor, so many C0045 repairs land around $100-$300. Wiring or connector repairs vary. On vehicles where the sensor is integrated into the wheel hub/bearing assembly, replacing the hub raises the cost. The sensor and its wiring are the most likely fix and should be checked first.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with wheel speed sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
Related repairs
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.