C0040 on Subaru
Right Front Wheel Speed Sensor Circuit
C0040 on Subaru vehicles indicates right front wheel speed sensor circuit. Au7o has documented this code across 1 Subaru model — most commonly on Forester. This is a brake/ABS-system code. The right front wheel speed sensor measures how fast that wheel is rotating and feeds that data to the anti-lock brake, traction control, and stability control systems. C0040 means the ABS module found an electrical problem in the right front wheel speed sensor circuit — for example an open circuit, a short, or a signal that is missing or out of range. You'll normally see the ABS and traction/stability lights come on, and those systems may shut off temporarily while your regular brakes keep working. Typical repair costs on Subaru range from $250 to $600, depending on the specific model and root cause.
Common Causes of C0040
- •Failed right front wheel speed sensor
- •Damaged, corroded or unplugged sensor wiring/connector
- •Damaged or rust-clogged tone/reluctor ring
- •Excessive air gap between sensor and tone ring
- •Wheel bearing wear affecting an integrated sensor
- •Water intrusion or corrosion at the connector
- •Faulty ABS control module (less common)
C0040 on Subaru by Model
Subaru Forester(1 issue)
- Premature Front and Rear Wheel Bearing/Hub Failure (Faulty Backing Plate Design)2009-2018
Forester wheel bearings (both front and rear hub assemblies) fail prematurely, often well before 100,000 miles. The most consistent symptom is a low-pitched grinding, humming or 'airplane' droning noise from the affected corner that grows louder with speed; rear bearing wear is often felt as a vibration under the seats. The noise typically changes pitch or volume during a left/right lane-change maneuver (which distinguishes it from differential whine). Subaru acknowledged a contributing root cause: unevenness/distortion of the bearing backing plate surface affects hub/bearing concentricity after the axle nut is torqued, allowing a 'howling' bearing to develop over time. Water/dirt contamination from failed seals and improper axle-nut torque accelerate the wear. Subaru issued a service bulletin acknowledging the rear bearing/backing-plate concern.
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What does C0040 mean on Subaru?▼
C0040 stands for "Right Front Wheel Speed Sensor Circuit." This is a brake/ABS-system code. The right front wheel speed sensor measures how fast that wheel is rotating and feeds that data to the anti-lock brake, traction control, and stability control systems. C0040 means the ABS module found an electrical problem in the right front wheel speed sensor circuit — for example an open circuit, a short, or a signal that is missing or out of range. You'll normally see the ABS and traction/stability lights come on, and those systems may shut off temporarily while your regular brakes keep working. On Subaru specifically, this code is documented across 1 model.
What causes C0040 on Subaru vehicles?▼
Common causes on Subaru: Failed right front wheel speed sensor, Damaged, corroded or unplugged sensor wiring/connector, Damaged or rust-clogged tone/reluctor ring, Excessive air gap between sensor and tone ring, Wheel bearing wear affecting an integrated sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix C0040 on a Subaru?▼
Repair costs on Subaru range from $250 to $600, depending on the specific model and root cause.
Which Subaru models have C0040 documented?▼
Au7o has documented C0040 on 1 Subaru model: Forester.