C0238: Wheel Speed Mismatch

What it means

This code has no generic meaning assigned by SAE J2012 or ISO 15031-6. Any description for it is manufacturer-specific.

How it works

C0238 has no generic OBD-II definition, so its title must be verified against the vehicle's own brake-control information. If this vehicle uses the title shown, the module compares wheel-speed readings and sets the code when they disagree beyond its monitored limits; the code alone does not identify which reading is wrong.

Common causes

Most likely first.

1. Manufacturer-specific diagnostic definition
2. Vehicle-specific scan-tool decoding

Symptoms

• Symptoms depend on the vehicle-specific meaning

How to diagnose it

1. Use a scan tool that reads the brake control module to confirm the vehicle-specific definition and retrieve any freeze-frame or event data.
2. Compare all four live wheel-speed readings at a steady, cautious low speed to find which reading differs from the others.
3. Check tire sizes, inflation, and obvious tire damage because mismatched rolling circumference can create a wheel-speed difference.
4. Inspect the sensor, wiring, connector, and tone ring or encoder at the wheel identified by the live data.
5. Test that wheel's sensor and circuit using the vehicle wiring diagram and manufacturer's specification, then check for bearing play if the signal remains inconsistent.

Common fixes

• Correct tire size or inflation differences that affect rolling circumference.
• Clean and secure the connector for the wheel with the inconsistent reading.
• Repair damaged sensor wiring or replace a damaged tone ring or encoder.
• Replace the confirmed faulty wheel-speed sensor or bearing.

Can I keep driving?

Drive cautiously because ABS or stability control may be reduced or unavailable while the mismatch is present. Avoid high speeds and slippery roads until the readings agree and the warning is resolved.