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.
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.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Signal Monitoring | ● External noise ● Faulty steering wheel sensor |
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. | |
Fail Safe | ● Inhibit the ESP control and allow the ABS/EBD control. ● The ESP warning lamp is activated. |
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.
Connect scantool to Data Link Connector(DLC).
Ignition "ON" & Engine "ON".
Turn the steering wheel to the left or right.
Monitor the "STEERING ANGLE SNSR" parameters on the Scantool.
Specification : If the parameters are changed according to wheel position during steering the wheel, it is normal condition.
Fig 1) Test Condition : Ignition "ON" & Engine "ON".
Normal Data
Fig 2) Test Condition : Ignition "ON" & Engine "ON".
Normal Graph
Fig 3) Test Condition : Ignition "ON" & Engine "ON".
Abnormal Graph
Whenever steering wheel is turned, is the steering sensor's scantool data changed?
 | ▶ Fault is intermittent caused by poor connection in steering sensor harness and/or HECU's connector or was repaired and HECU memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure. |
 | ▶ Go to "Terminal and Connector Inspection" procedure. |
Many malfunctions in the electrical system are caused by poor harness(es) and terminal condition. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
| ▶ Repair as necessary and then go to "Verification of Vehicle Repair" procedure. |
| ▶ Go to "Signal Circuit Inspection" procedure. |
Ignition "ON" & Engine "OFF".
Turn the steering wheel to the left or right.
Measure waveform between signal terminal of the HECU harness connector and chassis ground with osciloscope.
Specification : Check the voltage range (HIGH : 2.9±0.1V ~ 4.4±0.1V LOW : 1.2±0.1V ~ 2.1±0.1V) of the sensor signal in case of turning left, turning right, center position. If normal waveforms such as fig1, 2, 3 are detected in each condition, It is normal.
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" → "LOW") is detected when steering wheel is passing by on center position.
※ "LOW" : approx 1.5V, "HIGH" : approx 3.5V.
Is the measured waveform within specifications?
| ▶ Substitute with a known-good HECU and check for proper operation. If problem is corrected, replace HECU and then go to "Verification of Vehicle Repair" procedure. |
| ▶ Repair open or short in signal circuit between the steering angle sensor harness connector and HECU harness connector and then, go to "Verification of vehicle Repair" procedure. If there is no problem in Signal circuit, Substitute with a known-good HECU and check for proper operation. |
Ignition "ON" & Engine "ON".
Turn the steering wheel to the left or right.
Measure waveform between signal terminal of the steering angle sensor harness connector and chassis ground with osciloscope.
Specification : Check the voltage range (HIGH : 2.9±0.1V ~ 4.4±0.1V LOW : 1.2±0.1V ~ ±0.1V) of the sensor signal in case of turning left, turning right, center position. If normal waveforms such as fig1, 2, 3 are detected in each condition, It is normal.
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" → "LOW") is detected when steering wheel is passing by on center position.
※ "LOW" : approx 1.5V, "HIGH" : approx 3.5V.
Is the measured waveform within specifications?
| ▶ Fault is intermittent caused by poor connection in steering sensor harness and/or HECU's connector. Go to "Verification of vehicle Repair" procedure. |
| ▶ If STN signal is HIGH on center position, Check for improper installation of steering angle sensor. Repair as necessary and then go to "Verification of vehicle Repair" procedure. If sensor mounting state is normal, Substitute with a known-good steering angle sensor and check for proper operation. If problem is corrected, replace steering angle sensor and then go to "Verification of Vehicle Repair" procedure. |
After a repair, it is essential to verify that the fault has been corrected.
Connect scantool and select "Diagnostic Trouble Codes(DTCs)" mode
Using a scantool, Clear DTC.
Operate the vehicle within DTC Detecting Condition in General Information.
Using a scantool, Check DTC present.
Are any DTCs present ?
| ▶ Go to the applicable troubleshooting procedure. |
| ▶ System performing to specification at this time. |
