Component Location
General Description
The Steering wheel angle sensor uses two sensors ( A-sensor and B-sensor ) to determine the direction of the rotation.
The main components of each sensor are LED, photo transistor and slit plate.
The slit plate, which has 45 holes, is installed between LED and photo transistor, and generates signals if slit plate rotates according to the steering wheel rotation.
The sensor signals are generated by photo transistor which is driven whenever the light passes through the holes. The HECU detects operating speed and direction of the steering wheel by this input signal, and the signal is used to input signal for anti-roll control.
DTC Description
This monitoring function monitors the changing point of N-signal with measured steering angle from ST1 and ST2.
If N-signal changing point differs more than predefined degree, the failure is detected.
If there is no variation of the steering wheel angle for predefined time ECU detect the failure.
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
DTC Strategy | Signal Monitoring
| External noise Faulty steering wheel sensor
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Enable Conditions | The STN is low more than ±20 degrees for 70msec. When the steering wheel is turned more than 370±5 degrees, if center is not detected, ECU detects the failure. When the steering wheel angle is higher than 700 degrees ECU detects the failure. During straight driving, if the steering wheel angle is larger than 55±5 degree ECU detects the failure. When the curve is detected after driving straight, if there is no variation of the steering wheel angle for 3sec, ECU detect the failure. While the vehicle drive 60±5 degree ? -60±5 degree, if STN is not detected low, ECU detect the failure. While steering angle sensor wheel through center, if steering angle sensor is against specification three times, ECU detect the failure.
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Fail Safe | Inhibit the ESP control and allow the ABS/EBD control. The ESP warning lamp is activated.
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Diagnostic Circuit Diagram
Signal Waveform & Data
Fig 1) Normal waveform of steering angle sensor with turning left after ENG "ON" : Output signal change ("LOW" ? "HIGH") is detected first in ST1.
Fig 2) Normal waveform of steering angle sensor with turning right after ENG "ON" : Output signal change ("LOW" ? "HIGH") is detected first in ST2.
Fig 3) Normal waveform of steering angle sensor being center position after ENG "ON" : Output signal change ("HIGH (approx 3.5V)" ? "LOW") is detected when steering wheel is passing by on center position.
? "LOW" : approx 1.5V, "HIGH" : approx 3.5V.