C1781 Code: Meaning, Causes, and Symptoms | OBD2 Codes

C1781 – Steering Angle Sensor Circuit


C1781 Possible Symptoms


Anti-Lock Brake System (ABS) Warning Light ON,Engine Light ON (or Service Engine Soon Warning Light)


C1781 Possible Causes


Faulty Steering Angle Sensor,Steering Angle Sensor harness is open or shorted,Steering Angle Sensor circuit poor electrical connection,Faulty Suspension ECU


C1781 Description


The Steering Angle Sensor is fitted to the turn signal switch assembly and detects the steering rotating direction and angle. The sensor consists of a slit disc that rotates with the steering wheel as a unit, and a pair of photo interrupters. Each photo interrupter consists of an LED (Light Emitting Diode) and a photo transistor, which face each other. It converts the change in the light irradiation between the 2 elements to the on/off signals. The slit disc rotates between the LED and the photo transistor of the pair of photo interrupters. As the steering wheel is operated, the slit disc rotates with the wheel as a unit to stop and allow light transmission between the 2 elements. The pair of photo interrupters have phases and the suspension ECU detects the steering direction and angle based on the changes of each output. When it is judged that the steering wheel’s turning angle is large and the speed is greater than a set value, the ECU causes the damping force to increase.