What Does C0238 Mean?
C0238 indicates the Anti-lock Braking System (ABS) control module has detected a discrepancy between the rotational speeds of one or more wheels that exceeds acceptable parameters. This typically means one wheel speed sensor is reporting a significantly different speed than the others during vehicle operation. The ABS/traction control/stability control systems rely on accurate wheel speed data to function properly, and this mismatch will usually disable these safety systems until the fault is corrected.
Common Causes
35%
Faulty or contaminated wheel speed sensor providing erratic or incorrect signal
30%
Damaged, missing, or contaminated tone ring/reluctor ring on the hub or axle
15%
Incorrect tire size or mismatched tire diameters causing actual speed difference
12%
Damaged wheel speed sensor wiring harness or poor ground connection
8%
Excessive wheel bearing play or damaged hub bearing affecting sensor air gap
Diagnostic Steps
1
Step 1: Monitor live data for all four wheel speed sensors while driving at 15-25 mph on a straight road. Identify which sensor shows significantly different readings or erratic signal compared to the others.
2
Step 2: Perform visual inspection of the identified wheel speed sensor, connector, and wiring harness for physical damage, corrosion, or contamination from brake dust, metal shavings, or road debris. Clean sensor tip and check connector terminals.
3
Step 3: Inspect the tone ring/reluctor ring on the suspected wheel for missing teeth, cracks, damage, or excessive metallic debris buildup. Check sensor-to-tone ring air gap specification (typically 0.020-0.050 inches) using feeler gauge or per manufacturer specifications.
4
Step 4: Check wheel bearing play by raising vehicle and attempting to rock the wheel at 12 and 6 o'clock, then 3 and 9 o'clock positions. Excessive play indicates bearing failure affecting sensor accuracy.
5
Step 5: Measure tire circumferences or verify all four tires are the same size, type, and inflation pressure. Significant differences in tire diameter will cause speed mismatch codes.
6
Step 6: If sensor and tone ring are intact, test sensor resistance (typically 800-1400 ohms for passive sensors) and AC voltage output while spinning wheel by hand. Replace sensor if readings are out of specification or intermittent.
Estimated Repair Cost
$120 - $650
Parts + labor, varies by vehicle and location
C0238 indicates the Anti-lock Braking System (ABS) control module has detected a discrepancy between the rotational speeds of one or more wheels that exceeds acceptable parameters. This typically means one wheel speed sensor is reporting a significantly different speed than the others during vehicle...
The most common cause of C0238 (Wheel Speed Mismatch) is: Faulty or contaminated wheel speed sensor providing erratic or incorrect signal
Typical repair costs for C0238 range from $120 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle is generally safe to drive with normal braking function intact, but ABS, traction control, and stability control systems will be disabled, significantly reducing safety during emergency braking or slippery conditions. Repair should be completed within a few days to restore full safety system functionality.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C0238 to identify the root cause.
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Quick Info
Category
Chassis
System
Anti-lock Braking System (ABS) / Traction Control / Stability Control
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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