C0045 and C0046: Left Rear Wheel Speed Circuit Malfunction

C0045 and C0046 are diagnostic trouble codes (DTCs) that indicate a problem with the left rear wheel speed sensor or its circuit. The wheel speed sensor is a device that measures the rotational speed of the wheel and sends a signal to the electronic brake control module (EBCM).

The EBCM uses this information to adjust the brake pressure and prevent the wheels from locking up during braking.

The wheel speed sensor circuit consists of the sensor itself, the wiring, and the connectors. If any of these components are damaged, loose, corroded, or shorted, the circuit may malfunction and trigger the code C0045 or C0046. The code may also be set if there is a mismatch between the left rear wheel speed and the other wheels, which could indicate a faulty sensor or a mechanical problem with the wheel.

The codes C0045 and C0046 have different meanings depending on the type of malfunction detected by the EBCM:

• C0045: Left Rear Wheel Speed Circuit Malfunction
• C0046: Left Rear Wheel Speed Sensor Circuit Range/Performance (EBCM)

What causes C0045 and C0046 codes?

There are many possible causes for these codes, but some of the most common ones are:

• A faulty left rear wheel speed sensor
• A damaged or broken wire in the left rear wheel speed sensor circuit
• A bad ABS reluctor ring
• A loose or corroded connector in the left rear wheel speed sensor circuit
• A blown fuse or a bad relay in the left rear wheel speed sensor circuit
• A mismatched tire size or pressure on the left rear wheel
• A worn or damaged wheel bearing or hub on the left rear wheel
• A faulty EBCM

What symptoms may C0045 and C0046 codes produce?

Depending on the severity of the problem, these codes may cause one or more of the following symptoms:

• The anti-lock brake system (ABS) warning light may illuminate on the dashboard
• The traction control system (TCS) or the stability control system (SCS) may be disabled or malfunctioning
• The vehicle may pull to one side during braking
• The braking performance may be reduced or uneven
• The vehicle may experience vibrations or noises from the left rear wheel area

How to troubleshoot and fix C0045 and C0046 codes?

To diagnose and fix these codes, you will need some basic tools and equipment, such as:

1. A scan tool that can read and clear DTCs
2. A digital multimeter that can measure voltage and resistance
3. A jack and jack stands that can safely lift and support the vehicle
4. A visual inspection mirror and a flashlight that can help you inspect hard-to-reach areas

The following steps will guide you through a basic troubleshooting procedure for these codes:

• Scan the vehicle with your scan tool and retrieve any stored DTCs. Note down any other codes that may be related to these codes, such as C0035 (Left Front Wheel Speed Sensor Circuit), C0036 (Right Front Wheel Speed Sensor Circuit), or C0040 (Right Rear Wheel Speed Sensor Circuit). Clear all codes and test-drive the vehicle to see if these codes return.
• If these codes return, inspect the left rear wheel speed sensor visually. Look for any signs of physical damage, such as cracks, breaks, or corrosion. Check the mounting bolts and make sure they are tight and secure. Check the wiring harness and connectors for any signs of damage, such as cuts, abrasions, burns, or corrosion. Repair or replace any damaged components as needed.
• If the visual inspection does not reveal any obvious problems, test the left rear wheel speed sensor electrically. Disconnect the sensor connector and measure the resistance across the two terminals with your multimeter. Compare your reading with the specifications from your vehicle’s service manual. If the resistance is out of range, replace the sensor.
• If the resistance is within range, reconnect the sensor connector and measure the voltage across the two terminals with your multimeter. Spin the left rear wheel by hand and observe your reading. You should see an alternating current (AC) voltage that varies with the wheel speed. If you do not see any voltage or a constant voltage, replace the sensor.
• If you see a normal voltage from the sensor, test the wiring and connectors in the left rear wheel speed sensor circuit. Disconnect both ends of each wire in the circuit and measure the resistance with your multimeter. Compare your readings with the specifications from your vehicle’s service manual. If any wire shows an open circuit (infinite resistance) or a short circuit (zero resistance), repair or replace it.
• If all wires show normal resistance, test each connector in the circuit for continuity and corrosion. Clean any corroded terminals with electrical contact cleaner and a wire brush. Replace any damaged connectors as needed.
• If the wiring and connectors are good, test the fuse and the relay in the left rear wheel speed sensor circuit. Locate the fuse and the relay in the fuse box and check their condition. Replace any blown fuse or bad relay as needed.
• If the fuse and the relay are good, test the EBCM for proper operation. Connect your scan tool to the vehicle and access the live data from the EBCM. Monitor the left rear wheel speed sensor signal and compare it with the other wheel speed sensors. If the signal is erratic, missing, or incorrect, replace the EBCM.

Conclusion

C0045 and C0046 are common DTCs that indicate a problem with the left rear wheel speed sensor or its circuit. They can cause various symptoms, such as reduced braking performance, disabled traction or stability control, or dashboard warning lights. To diagnose and fix these codes, you will need to follow a systematic troubleshooting procedure that involves visual inspection, electrical testing, and component replacement. By following this article, you should be able to diagnose and solve these codes with ease.

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