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  • A faulty wheel speed sensor, wiring issues, a shorted or open harness, and anti-lock braking system (ABS) module problems are most likely to trigger a C0045 code.
  • If left unaddressed, your vehicle’s left rear wheel could slip and eventually lock up.
  • If your vehicle’s computer logs this code, it might exhibit symptoms like an illuminated ABS warning light, activated stability and traction control lights, and a disabled ABS.

The wheel speed sensor is a variable reluctance device usually mounted to the steering knuckle, wheel hub, brake backing plate, transmission tailshaft, or differential housing. It monitors the wheel speed and sends input to the anti-lock control module whenever one wheel starts to slow down at a faster rate than the others. This means that the affected wheel is starting to slip and is at risk of locking up.

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A faulty wheel speed sensor, particularly the one mounted to the left rear wheel, won’t be able to send signals to the control module and can trigger the C0045 code.

What Does the C0045 Code Mean?

Diagnostic trouble code (DTC) C0045 stands for “Left Rear Wheel Speed Circuit Malfunction.”

Wheel speed sensors are typically made up of a magnetic pickup and toothed sensor ring or tone ring.

car wheel speed sensors
A faulty wheel speed sensor, particularly the one mounted to the left rear wheel, won’t be able to send signals to the control module and can trigger the C0045 code.

As the wheel turns, the teeth on the sensor ring move through a magnetic field, producing an alternating current (AC) voltage in the sensor windings. The number of voltage pulses per second induced in the pickup changes frequency, which means that the frequency of the signal is directly proportional to the wheel speed. As the frequency gets higher, the wheel moves faster.

The anti-lock control module counts the pulses from the wheel speed sensor, monitoring the frequency signal and comparing its input with the rest of the sensors. If the control module detects an abrupt change in frequency signal, it will apply the anti-lock braking function to keep the vehicle stabilized.

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Note: The definition of code C0045 might differ depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the C0045 Code?

What are the Common Symptoms of the C0045 Code?

How to Diagnose the C0045 Code

DTC C0045 is an ABS-related code that can be logged in vehicles with on-board diagnostics (OBD). While this might be the case, keep in mind that your vehicle can exhibit symptoms that are different from other makes and models.

If you’re not familiar with the process of diagnosing trouble codes, it’s best to take your vehicle to a certified professional to ensure that all steps are followed correctly. Otherwise, you can go ahead and do the job yourself.

See also  C0040 Code: Right Front Wheel Speed Circuit Malfunction

Before you start, you might want to check out the video below to get an idea of what the process might involve.

How to Fix the C0045 Code

Attempting to fix a C0045 code can be difficult especially if you don’t have the right information. If you’re not confident with your DIY skills yet, it’s a good idea to bring your vehicle to the nearest repair shop and have it checked by a professional. But if you think you have the right tools and know-how, you can begin the repair process by checking out vehicle-specific repair guides like those from Chilton or an ALLDATA subscription for your convenience.

About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Contact Center Manager and Technical Reviewer at

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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