Open or Short in Front Speed Sensor LH Circuit — Left-Front ABS Wheel-Speed Sensor (Toyota/Lexus)

C1406 is the left-front wheel speed sensor circuit. On Toyota the usual cause is not the sensor itself but the harness where it runs down to the knuckle - it flexes with the suspension and chafes, and road salt corrodes the connector and the sensor's mounting bore in the steering knuckle. Inspect the connector pins for corrosion, bent or pushed-out terminals before buying anything. Clean the sensor's mounting bore too: rust scale behind the sensor lifts it away from the tone ring and produces the same fault. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.

Same left-front wheel speed sensor circuit, but do not test it the way you would an older sensor: these Lexus models use digital (active) speed sensors, so a simple resistance check across the terminals tells you nothing useful. They need a square-wave signal check with a scope or a scan tool that graphs live wheel speed while the wheel is turned. Plenty of good sensors get replaced on these cars because someone ohmed them and read an open. Check the connector and harness for corrosion first. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.