Cause
Worn wheel bearing
A hub bearing that has developed play or roughness — and a cause that reaches further than most people expect, because on many vehicles the wheel speed sensor is built into the bearing.
That is why it belongs on a list of electrical-sounding faults. Play at the hub changes the gap between sensor and tone ring as the wheel turns, so the signal weakens and strengthens once per revolution. The result reads exactly like a failing sensor, and replacing the sensor changes nothing.
The magnetic encoder ring is usually part of the bearing seal too, so a bearing fitted the wrong way round, or one whose encoder was scratched or wiped during fitting, produces a wheel speed fault on a brand-new part.
The mechanical symptoms are the giveaway when they are present: a droning or rumbling that changes with speed, and often changes as the car is steered — loading the bearing by cornering makes it louder or quieter. Rocking the wheel at twelve and six o'clock with the car raised finds obvious play.
But it can produce the electrical fault with no noise at all, which is the case worth remembering.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (12)
Codes where this is a likely explanation first, rather than merely a possible one.
- C0030 Left Front Tone Wheel Likely for this code Moderate
- C0033 Right Front Tone Wheel Likely for this code Moderate
- C0036 Left Rear Tone Wheel Likely for this code Moderate
- C0039 Right Rear Tone Wheel Likely for this code Moderate
- C003C Rear Tone Wheel Likely for this code Moderate
- C006B Stability System Active Too Long Likely for this code Moderate
- C0031 Left Front Wheel Speed Sensor Moderate
- C0034 Right Front Wheel Speed Sensor Moderate
- C0037 Left Rear Wheel Speed Sensor Moderate
- C003A Right Rear Wheel Speed Sensor Moderate
- C003D Rear Wheel Speed Sensor Moderate
- P2161 Vehicle Speed Sensor B Circuit Intermittent/Erratic/High High
Information, not instruction
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