What Does C0045 Mean?
This code indicates the Anti-lock Brake System (ABS) control module has detected an abnormal signal or loss of signal from the left rear wheel speed sensor. The wheel speed sensor monitors the rotational speed of the wheel and sends this information to the ABS module for traction control, stability control, and anti-lock braking functions. When the circuit is malfunctioning, the ABS module cannot accurately determine the left rear wheel's speed, causing the system to disable ABS and related safety features.
Common Causes
35%
Damaged or contaminated wheel speed sensor due to road debris, metal shavings, or physical impact
30%
Broken, corroded, or chafed wiring between the wheel speed sensor and ABS module
20%
Excessive air gap between wheel speed sensor and tone ring due to bearing wear or improper installation
10%
Damaged or missing teeth on the tone ring (reluctor ring) mounted to the hub or axle
5%
Failed ABS control module internal circuit or poor ground connection
Diagnostic Steps
1
Step 1: Perform visual inspection of the left rear wheel speed sensor, wiring harness, and connector for physical damage, corrosion, water intrusion, or loose connections. Check for debris or metal shavings accumulated on the sensor tip.
2
Step 2: Measure the resistance of the left rear wheel speed sensor using a digital multimeter across the sensor terminals (typical range 800-1400 ohms for passive sensors, or verify power and ground for active sensors). Compare readings to manufacturer specifications and the right rear sensor for reference.
3
Step 3: Inspect the tone ring for missing, damaged, or bent teeth, and verify proper air gap between sensor and tone ring (typically 0.020-0.050 inches). Rotate the wheel by hand and check for wobble or runout indicating bearing wear.
4
Step 4: Test the sensor signal circuit by back-probing the connector and monitoring AC voltage output while rotating the wheel slowly (passive sensors should produce 50-300mV AC), or verify square wave signal pattern with an oscilloscope for active sensors.
5
Step 5: Check wiring continuity from the sensor connector to the ABS module connector using a multimeter, and verify there is no short to ground or short to power in the circuit. Inspect for chafed wires along the suspension and frame rail.
6
Step 6: Clear the code and road test the vehicle while monitoring live data for the left rear wheel speed sensor signal to verify repair, ensuring the sensor produces consistent speed readings that match other wheels during acceleration and deceleration.
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This code indicates the Anti-lock Brake System (ABS) control module has detected an abnormal signal or loss of signal from the left rear wheel speed sensor. The wheel speed sensor monitors the rotational speed of the wheel and sends this information to the ABS module for traction control, stability ...
The most common cause of C0045 (Left Rear Wheel Speed Circuit Malfunction) is: Damaged or contaminated wheel speed sensor due to road debris, metal shavings, or physical impact
Typical repair costs for C0045 range from $100 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle is drivable but ABS, traction control, and stability control systems will be disabled, increasing stopping distances on slippery surfaces and reducing control during emergency maneuvers. Repair should be completed promptly, especially before driving in adverse weather conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C0045 to identify the root cause.
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Quick Info
Category
Chassis
System
Anti-lock Brake System (ABS) / Vehicle Stability Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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