C0045 Code: Left Rear Wheel Speed Sensor Circuit
The ABS module lost a valid signal from the driver-side rear wheel speed sensor.
Unverified: this manufacturer-specific definition comes from a single source or varies by model. Confirm it with a brand-specific scan tool.
Safety first · Consult a professional
- Braking system affected: ABS may be disabled. Drive carefully and have it checked promptly.
At a glance
Severity: Moderate
- Meaning
- Left Rear Wheel Speed Sensor Circuit
- System
- Brakes, ABS & Chassis · Chassis
- Safe to drive?
- With caution
- Typical repair cost
- $0–$550
- DIY difficulty
- Moderate
On GM and many other vehicles that follow the GM-style list, C0045 points to the left rear (driver-side rear) wheel speed sensor circuit. The rear sensors live in a harsh spot: the lead runs along the axle beam or trailing arm, often through a connector under the car or inside under the rear seat, and on front-wheel-drive cars the sensor frequently reads a magnetic ring in a bolt-on rear hub bearing. When the module loses or distrusts this signal it disables ABS, traction and stability control. Note that the newer SAE list uses C0045 for 'Brake Pressure Sensor B', so check the description your scan tool shows before buying parts.
Can I keep driving? The car brakes normally, but ABS is off and the rear can step out if the left rear wheel locks on a slippery surface. Drive gently, especially in rain or snow, and plan the repair soon.
How to read C0045
- C Chassis
- 0 Generic (SAE)
- 0 Brakes, ABS & Chassis
- 45 Specific fault
Symptoms
- ABS and traction/stability lights on, sometimes only after the first few miles
- ABS pulses at walking pace over rough pavement or manhole covers
- Warning comes and goes with wet weather or after a car wash
- Grinding or humming from the rear left that rises with speed
- Electronic parking brake or hill-hold warnings on some vehicles
- Damp carpet or water in the spare-wheel well on vehicles with an interior sensor connector
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Worn rear hub bearing unit or damaged magnetic encoder ring (typical of front-wheel-drive rear hubs)
- Sensor lead broken or chafed along the axle beam or trailing arm, often where rusted clips let it flap
- Corroded connector under the body or inside the cabin from water leaks
- Failed left rear sensor
- Rust scale under the sensor or a cracked pressed-on tone ring on the hub or drum
- ABS module input fault
Diagnosis step by step
Check the definition and watch the rear signals
Confirm your scan tool describes C0045 as the left rear wheel speed sensor. Watch left rear against right rear on a rough road at 5-15 mph; a signal that jumps on bumps points to loose wiring or a bearing with play.
Tools: OBD-II scanner
Trace the lead to the connector
Follow the sensor cable from the hub along the axle to its connector. Many cars place this connector under the rear seat or behind the trunk trim, so lift the carpet and look for moisture from leaking tail-light gaskets or door seals.
Tools: Flashlight, Screwdriver
Measure a passive sensor
Older rear sensors are often passive two-wire types. Measure resistance at the connector and compare with the right rear; they should be within about 10 percent of each other, and spinning the wheel by hand should give a small AC voltage that rises with speed.
Tools: Multimeter
Inspect the hub and encoder
With the wheel and drum or rotor removed, check the tone ring or magnetic ring for cracks, rust lifting it, or stuck metal debris. On bolt-on hub units the encoder sits inside the bearing seal, so damage there means replacing the hub assembly.
Tools: Flashlight, Soft brush
Check bearing play
Rock the raised wheel at 12 and 6 o'clock and spin it while listening. A rear bearing with play lets the encoder wobble away from the sensor, and a new sensor won't cure that.
Repair and test drive
Clip the lead back along its original route, torque hub bolts to spec, clear codes and drive over mixed surfaces. On cars with an electronic parking brake, use the scan tool's service mode before removing the rear caliper.
Tools: Torque wrench, OBD-II scanner
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Clean sensor bore and tone ring, secure lead | Yes | $0–$120 |
| Replace left rear wheel speed sensor | Yes | $80–$260 |
| Repair connector or wiring and fix water leak | No | $100–$350 |
| Replace rear hub bearing unit | No | $220–$550 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Field data
| Chevrolet | 2 | Equinox, Traverse |
|---|
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Depends
This ABS code doesn't affect an OBD emissions test. In states with a periodic safety inspection, an ABS light that stays on can be grounds for failure.
Frequently asked questions
Is the left rear the driver side?
Yes. Sides are always named from the driver's seat, so left rear is behind the driver on US vehicles. The right rear wheel has its own code, C0050.
My scanner calls C0045 a brake pressure sensor. Why?
The newer SAE list assigned C0045 to brake pressure sensor B, while GM-style numbering uses it for the left rear wheel speed sensor. Trust the description your scan tool shows for your vehicle.
Why does ABS kick in on bumpy roads at low speed?
A weak or intermittent left rear signal looks to the module like a wheel suddenly slowing, so it releases brake pressure. You feel this as pulsing just before you stop, often over potholes or cobbles.
Could a water leak really cause this code?
Yes. On cars where the rear sensor connector sits under the seat or behind the trunk trim, water from a leaking tail light or seal collects there and corrodes the pins. Fix the leak or the code will return.
Sources
- SAE J2012 – Diagnostic Trouble Code Definitions
- Manufacturer public service information (cross-checked)
- NHTSA Complaints API
- Methodology: How We Build Code Pages · Data Sources We Use · Editorial Policy