Most wheel speed sensors (except for the latest generation of “active” WSS sensors) won’t generate a readable signal until a vehicle is traveling 3 to 5 mph or faster. The scan tool will display a speed input in miles per hour (mph) for each wheel speed sensor. Most scan tools will allow you to not only read and clear the ABS codes that have turned on the ABS warning light, but to also look at the individual WSS inputs (Performance Information Data or PIDs). On some newer vehicles, “plausibility” codes may also be set if the speed reading of any WSS sensor differs from the vehicle speed sensor by more than 3 to 5 mph. On older ABS systems, a fault code is typically set if there is a loss of a signal in a WSS circuit (shorted or open), or the reading from one WSS sensor differs significantly from the rest. This might be the result of an intermittent signal or a noisy signal that is confusing the system control module. In some situations, it is also possible that the signal from a WSS may not be bad enough to set a fault code, but may be off enough to upset the normal operation of the ABS, traction control or stability control systems.
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