General Information

Engine Control

P0502 Vehicle Speed Sensor 'A' Circuit Low Input - General Information

Component Location





General Description

The Wheel Speed Sensor (WSS) generates a waveform with a frequency proportional to the speed of the vehicle. The signal generated by the WSS informs the ECM not only if the vehicle speed is low or high but also if the vehicle is or is not moving. The ECM uses this signal to control the fuel injection, ignition timing, transaxle shift scheduling and torque converter clutch scheduling. The WSS signal is also used to detect rough road conditions.

DTC Description

If there is no change of vehicle speed signal over 10 sec under driving, ECM sets P0502.

DTC Detecting Condition





Diagnostic Circuit Diagram





Signal Waveform & Data




Fig.1) Normal waveforms of VSS (from ESC (ESP) ECU-5 KM/H)