Damaged or corroded wiring or connector at the left rear wheel speed sensor; Failed left rear wheel speed sensor; Debris or metallic particles on the sensor tip or tone ring; Damaged or missing teeth on the tone ring (reluctor wheel); Excessive air gap between the sensor and tone ring due to worn hub or bearing; Faulty ABS control module (less common); Electrical interference or poor ground connection

DTC codes / C00xx · Brakes, steering and suspension / C0045

C0045Left Rear Wheel Speed Sensor Circuit Malfunction

Q: What does code C0045 mean?

Left Rear Wheel Speed Sensor Circuit Malfunction. The C0045 code indicates that the anti-lock brake system (ABS) control module has detected a malfunction in the left rear wheel speed sensor circuit, which can include an open circuit, short to ground or power, or an erratic signal. The computer monitors the sensor's output and sets this code when the signal is missing, out of range, or inconsistent with the other wheel speed sensors.

The C0045 code indicates that the anti-lock brake system (ABS) control module has detected a malfunction in the left rear wheel speed sensor circuit, which can include an open circuit, short to ground or power, or an erratic signal. The computer monitors the sensor's output and sets this code when the signal is missing, out of range, or inconsistent with the other wheel speed sensors.

SystemChassis

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaBrakes, steering and suspension

Symptoms you may notice

Illumination of the ABS warning light on the dashboard
Traction control or stability control warning light may also turn on
Often no symptoms besides the warning light
ABS may be disabled, leading to longer stopping distances on slippery surfaces
Possible intermittent or permanent loss of speedometer accuracy if the sensor is used for that function
In some vehicles, the transmission may shift erratically or the cruise control may not engage

Common causes, most likely first

Damaged or corroded wiring or connector at the left rear wheel speed sensor
Failed left rear wheel speed sensor
Debris or metallic particles on the sensor tip or tone ring
Damaged or missing teeth on the tone ring (reluctor wheel)
Excessive air gap between the sensor and tone ring due to worn hub or bearing
Faulty ABS control module (less common)
Electrical interference or poor ground connection

How to diagnose and fix it

Inspect the left rear wheel speed sensor and its wiring for visible damage, corrosion, or loose connections
Clean the sensor tip and tone ring of any debris or metallic particles
Check the tone ring for missing or damaged teeth
Measure the resistance of the wheel speed sensor and compare to specifications
Perform a voltage drop test on the sensor circuit while wiggling the harness to check for intermittent faults
Use a scan tool to monitor live wheel speed data and compare the left rear sensor to the other wheels while driving
If all else checks out, diagnose the ABS control module or replace the sensor as needed

Common misdiagnosis traps for C0045

A dirty or debris-covered sensor tip is a frequent cause that is often overlooked, so cleaning it before replacement can save time and money.
The tone ring may be integrated into the wheel bearing or hub assembly on some vehicles, so a damaged ring might require replacing the entire hub.
Intermittent faults can be caused by a broken wire inside the insulation that only acts up when the suspension moves, so a wiggle test is essential.
The ABS control module rarely fails, but a poor ground connection can mimic a sensor fault, so always check grounds before condemning the module.
This code can be set by a mismatched tire size or uneven tire wear, which affects wheel speed readings and triggers the sensor circuit malfunction.

Can I keep driving with C0045?

You can usually continue driving with the ABS light on, but the anti-lock braking system may be disabled, increasing stopping distances in emergency situations. Avoid driving in slippery conditions or at high speeds until the fault is repaired, and be prepared for reduced braking performance.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.