Code Parameters

Code 21 sets if left front speed signal is less than 50 percent of other wheel speeds. This code may set any time vehicle is moving faster than 5 MPH (8 km/h) and is not in ABS braking. This code may be set together with Code 25. Failure may first appear to be an intermittent short or open which sets Code 25. Subsequent complete failure may then set Code 21. Drive vehicle faster than 40 MPH (64 km/h) to check for reappearance of failure.