Possible causes
– Faulty Vehicle Speed Sensor
– Vehicle Speed Sensor harness is open or shorted
– Vehicle Speed Sensor circuit poor electrical connection
– Vehicle Speed Sensor harness is open or shorted
– Vehicle Speed Sensor circuit poor electrical connection
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
P1540 SUBARU OBD Code Description
The Vehicle Speed Sensor 1 (Output Shaft Rotation Sensor) is mounted to the extension case (from the outside of the case). the sensor outputs a pulse signal which is transmitted to the Transmission Control Module (TCM) where it is converted to vehicle speed.
The transfer clutch drum is connected directly to the rear wheel driving propeller shaft. Vehicle speed sensor 1 on the AWD model detects rear-wheel speed.