DTC C1260 Steering Angle Sensor-Signal: DTC Detecting Condition

DTC DETECTING CONDITION CHART

Item		Detecting Condition	Possible cause
DTC strategy		Voltage Monitoring	Open or short of steering angle sensor circuit Inoperative steering angle sensor Inoperative HECU
Case 1	Monitoring Period	Continuous
Case 1	Enable Conditions	During normal driving conditions the long time filtered driving direction is straight ahead. The long time filtered SAS-value is equivalent to the offset. If the offset value exceeds a threshold of approximately 15 deg a SAS-fault is determined. Failure detection time depends on the driving distance, vehicle speed and on the amount of failed SAS signal. Within 30 km of symmetrical driving the calculated offset corresponds to the sensor offset.
Case 2	Monitoring Period	Continous (If the following conditions are satisfied) After SAS-initialization and vehicle reference speed > 1.4 m/s No under voltage At least one SAS-message was sent in the current 20 ms-cycle.]
Case 2	Enable Conditions	A SAS-gradient-failure is set, if Signal gradient (steering angle velocity) from one 20 ms-cycle to another is higher than 40° or Change of this gradient (steering angle acceleration) is higher than 15°: \| (LwInK0K1 . LwInK1K2)\| > 15° and \| (LwInK0K1 + LwInK1K2)\| > 15° LwInK0K1: Difference of the SAS-signal between the current 20 ms-cycle and the last 20 ms-cycle. LwInK1K2: Difference of the SAS-signal between the last 20 ms-cycle and 20 ms-cycle before.
Case 3	Monitoring Period	Continuous (After initialization and no under voltage detected)
Case 3	Enable Conditions	If value is higher than 665° + 90° tolerance for more than 300 ms a fault is determined.
Case 4	Monitoring Period	Continuous (during driving)
Case 4	Enable Conditions	Based on a vehicle model a reference SAS signal is build. The difference between measured SAS signal and SAS signal calculated from yaw-rate sensor signal is evaluated for fault detection. Dependent on the driving conditions failures in size of [10 + 60 m/s / vehicle reference speed] deg at steering angle are recognized within 400 ~ 4800 ms through three possible recognition paths: Curve Branch (lateral G > 2 m/s² and left and right curve driving) Stability Branch (no large wheel speed differences and stable acceleration) Straight ahead Branch (lateral G < 0.5 m/s² and yaw rate < 2 deg/s). The recognition time depends on the active branch (the time is shorter in a relation 1.:2.:3.-4:2:1) and the value of the permissible time threshold dependent on the deviation between the compared signals (small deviation → long detection time, large deviation → small detection time).
Case 5	Monitoring Period	Initialization once in every ignition cycle. The monitoring is active until a reset by a change in the SAS signal or until a right and left cornering can be recognized.
Case 5	Enable Conditions	If there is no change in the signal, but a right and left cornering has been recognized, a fault is determined, (lateral G > 2 m/s² in combination with a yaw rate > 6°/s in both directions). At a minimum change of e.g. 5° in the signal, the monitoring is reset.
Case 6	Monitoring Period	Continuous (during driving)
Case 6	Enable Conditions	The measured yaw rate and the yaw rates, calculated from the wheel speed sensor and SAS are compared. If the signals don't fit and forwards driving is detected, a fault is determined.
Case 7	Monitoring Period	Continuous (during driving)
Case 7	Enable Conditions	Under normal conditions, two SAS messages are sent in one 20 ms cycle, which is shown by an increase of the message counter by 2. If the message counter shows an increase higher than 3 or lower than 1 in one 20 ms-cyle, a fault is stored after 160 ms.
Fail Safe		Reduced controller function caused by inoperative SAS signal. ABS/EBD control is available. The ESC warning lamp is activated.