AHLS provides driver with the best visibility by adjusting vertical direction of the headlamp. It consists of AHLS ECU, Linkage and actuator. The AHLS ECU detects the vehicle speed to use it as a compensation factor for the actuator control. In other words, when the vehicle speed is low the acutator needs to respond slowly though the linkage of height sensor moves quickly (response filter value is high). But when the vehicle speed is high, AHLS ECU operates the actuator quickly in proportion to the height sensor variation.
The AHLS ECU sets DTC C1212 if the speed signal line carries a higher frequency than defined maximum value(approx. 180Hz) for 1.5 ± 0.5 seconds.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Frequency check | 1. Poor connection 2. Faulty Vehicle speed signal line 3. AHLS-ECU faulty |
Detecting mode |
•
When vehicle is driving | |
Threshold Value |
•
Frequency > 180Hz | |
Detecting time |
•
1.5s ± 0.5s | |
Fail Safe |
•
Error detected during power-up : maintain the current status. - none of the AHLS's output(OFF)
•
Error detected during normal operation : maintain the current status. - maintainance of the AHLS's output |
Fig.1) It shows Signal waveform at driving condition that changes frequency according to vehicle speed.
