C0045 Code: Left Rear Wheel Speed Sensor Circuit Failure

What the C0045 code means

The ABS module (EBCM) controls the anti-lock brakes and, on most modern vehicles, traction control and stability control too. When it detects a fault, it disables those functions and turns on the ABS and stability warning lights. The normal brakes keep working.

Each wheel has a sensor that measures its speed by reading a toothed or magnetic ring on the hub or axle shaft. The C0045 code refers to the left rear wheel. A circuit fault points to a cut wire, a damaged connector, or a sensor that is open or shorted.

Always start with the simplest things: fuse, relay and connector. Then check supply, ground and signal with the component connected (back-probing), and finally the continuity of each wire up to the computer. Only if all of that is good should you replace the component.

Important: many C and B codes are not generic. The definition on this page is the most widespread one, used by General Motors and most generic scan tools, but on other makes the same number can mean something else. Always confirm the code text with a scan tool that reads the right module (ABS, body or airbag).

A quick check: lift the vehicle, turn the wheel by hand with the scan tool connected and see whether a speed shows up for that wheel. If nothing appears, the problem is electrical (sensor or cable). If it appears but drops out now and then, look at the ring and the bearing play.

C0045 code symptoms

• ABS and stability control warning lights on.
• The ABS does not act, or acts at low speed when it is not needed.
• An erratic speedometer on some vehicles.
• Cruise control may be disabled.

Likely causes of the C0045 code

1. Damaged sensor cable. It runs through the suspension and breaks with the movement.
2. Corroded connector exposed to road water and salt.
3. Sensor open or shorted. The coil or the internal electronics of the sensor were damaged, often by impacts or by heat from the brakes.
4. ABS module. Uncommon.

How to diagnose the C0045 code step by step

1. Read the speed of all four wheels on the scan tool while driving slowly in a straight line. They should match.
2. Inspect the cable and connector along their whole length, especially around the suspension.
3. Remove the sensor and clean its tip and its bore.
4. Check the ring for broken teeth, cracks or rust.
5. Passive sensor: measure the resistance. A typical figure is 800 to 2,000 ohms.
6. Active sensor: check the supply from the module and the signal with the scan tool.
7. Turn the wheel by hand with the scan tool connected. A low, steady speed should appear.

How to fix the C0045 code

• Clean the sensor and the ring.
• Repair the cable or the connector.
• Replace the sensor, or the bearing if the ring is built into it.
• Clear the codes and confirm on a road test that the warning light goes out.

Technical reference data

• Passive sensor: 800 to 2,000 ohms.
• Active sensor: current signal of roughly 7 and 14 mA.
• These values are approximate. Check the manufacturer data for your vehicle.

Brand-specific notes

If the C0045 code appeared right after brake or bearing work, suspect a sensor that was knocked or not seated properly before looking at anything else.

C0045 on Toyota, Honda, Hyundai and Chevrolet

On many vehicles from these makes the magnetic ring is built into the wheel bearing. If the bearing is installed backwards, the sensor cannot read it.

Frequently asked questions about C0045