DTC C1781/81: Steering Angle Sensor Circuit: Description

WARNING: This page is about a different car, the 2007 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.

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, located facing 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 and shuts and makes the 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 the each output.

And 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.

Fig 1: Identifying Steering Angle Sensor Circuit

DTC DETECTION CONDITION TABLE

DTC No.	DTC Detection Condition	Trouble Area
C1781/81	Steering angle 36° or larger signal does not input	Steering angle sensor Suspension control ECU Wire harness