General Information

Automatic Headlamp Leveling System
C1212 Vehicle Speed Sensor Failure - 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 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.

DTC Description

The ECM sets DTC C1212 if the speed signal line carries a higher frequency than defined maximum value(approx. 420Hz) for 2 seconds.

DTC Detecting Condition





Diagnostic Circuit Diagram





Signal Waveform & Data




Fig.1) It shows Signal waveform at driving condition that changes frequncy according to vehicle speed.