C0040 on Toyota: How to Diagnose & Fix
Right Front Wheel Speed Sensor Circuit
1 Toyota model · 1 documented issue · $20-$700 repair
C0040 on Toyota by model: symptoms, diagnosis and fix
A very common Yaris electrical fault: the rear wheel speed sensor is integrated into the rear hub/bearing assembly and is not sold separately. The weather seal where the harness plugs into the hub has a gap, so road spray and winter salt wick into the connector, corrode the pins and degrade the signal. The ABS light and the red brake/'!' light come on together, often intermittently at first and worse in wet or winter weather. Dealers routinely quote a complete rear hub assembly (owners report $650-750 CAD per side) when the actual fault is frequently just a dirty, corroded connector.
Common Symptoms
- ABS light and red brake/'!' light on together
- Lights come on intermittently, worse in rain, snow or after driving on salted roads
- ABS unavailable, traction/stability warning
- Speed sensor circuit code stored for one rear wheel
How to Fix
Before buying a hub: unplug the rear speed sensor connector at the hub, clean the corrosion out of both halves with electrical contact cleaner, inspect the pins, repack with dielectric grease and seal the harness gap so spray can't re-enter. Check the harness routing for chafe points along the trailing arm too. If the pins are already eaten away or the sensor reads open/erratic on a scan tool, the rear hub/bearing assembly must be replaced as a unit - the sensor is not serviceable separately.
Sources for this issue (3)
C0040 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does C0040 mean on a Toyota?
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 Toyota it is documented across 1 model: Yaris.
What are the most common causes of C0040?
The most common causes of C0040 are: 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). The specific cause varies by vehicle.
How much does it cost to fix C0040 on a Toyota?
Published repair estimates on Toyota range from $20 to $700 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for C0040 on a different make?
View C0040 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.