General Information

Head Lamp

Automatic Headlamp Leveling System - C1212 Vehicle Speed Sensor - General Information

Component Location





General Description

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 actuator needs to repond slowly though the linkage of height sensor moves quickly (response filter value is high). But when the vehicle speed is high, ECM operates the actuator quickly in proportion to the height sensor variation.

DTC Description

The ECM sets DTC C1212 if the speed signal line carries a higher frequency than defined maximum value (approx. 300 Hz) for 2 seconds

DTC Detecting Condition





Schematic Diagram





Signal Waveform




Fig.1) The waveform of speed signal at 28 MPH
Fig.2) The waveform of speed signal at 57 MPH