General Information

Auto 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 The AHLS ECU, Linkage and actuator. The The AHLS ECU 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, The AHLS ECU operates the actuator quickly in proportion to the height sensor variation.

DTC Description

The The AHLS ECU sets DTC C1212 if the speed signal line carries a higher frequency than defined maximum value (approx. 180 Hz) for 1.5±0.5 seconds.

DTC Detecting Condition





Diagnostic Circuit Diagram










Signal Waveform & Data




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