AHLS provides driver with the best visibility by adjusting vertical direction of the headlamp. It consists of ECM, Linkage and actuator. The ECM detects the vehicle speed to use it a compensation factor for the actuator control. In other words, when the vehicle speed is low the acutator needs to repond slowly though the linkage of height sensor moves quickly (reponse filter value is high). But when the vehicle speed is high, ECM operates the actuator quickly in proportion to the height sensor variation.
The ECM sets DTC C1212 if the speed signal line carries a higher frequency than defined maximum value(approx. 300Hz) for 2 seconds.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Frequency check | 1. Poor connection 2. Faulty vehicle speed sensor 3. AHLS-ECM faulty |
Detecting Mode |
•
IG KEY ON, ENGINE ON, HEAD LAMP ON | |
Threshold Value |
•
Frequency > 300Hz | |
Detecting Time |
•
2 sec. |
Fig.1) It shows signal waveform at driving condition that changes frequency according to vehicle speed.