Automobile & Light Truck Certification Test A5 BrakesAnti-lock Brake System (ABS) Diagnosis and RepairMedium
A technician is diagnosing an ABS warning light and a C0070 fault code: 'Steering Angle Sensor (SAS) Circuit'. The vehicle also has an intermittently working stability control (ESC) system. The SAS is a critical input for the ESC system. What information does the SAS primarily provide to the ABS/ESC control module?
- AThe driver's intended direction of travel.
- BThe hydraulic pressure in the power steering system.
- CThe vehicle's lateral acceleration.
- DThe rotational speed of the steering wheel.
Show answer & explanationAnswer & explanation
Correct answer: A. The driver's intended direction of travel.
The steering angle sensor measures the absolute position of the steering wheel and its rate of rotation. This directly tells the ABS/ESC control module the driver's intended direction, which is then compared to the vehicle's actual movement (from yaw rate and lateral acceleration sensors) to detect understeer or oversteer.
Why the other options are wrong
- B. The hydraulic pressure in the power steering system is monitored by different sensors, not the steering angle sensor.
- C. Lateral acceleration is measured by a separate lateral accelerometer, not the steering angle sensor.
- D. While it measures rotation, its primary output for ESC is the absolute angle, indicating the driver's intended path, not just the speed of rotation.
Steering Angle Sensor (SAS)
A sensor that measures the absolute angular position and often the rate of rotation of the steering wheel. It provides the ABS/ESC control module with the driver's intended direction of travel, which is crucial for stability control calculations.
- Measures steering wheel position.
- Indicates driver's intended path.
- Critical input for ESC and traction control.
Memory trick: SAS: ESC's Intent Interpreter!