With Manual Transmission

DTC P0502






Circuit Description

Vehicle speed information is provided to the engine control module (ECM) by the vehicle speed sensor (VSS). The Hall-Effect sensor contains a permanent magnet and a semiconductor plate to which ignition voltage is applied. As the output shaft spins, the rotor directs the field of the permanent magnet either toward or away from the plate. When the ignition is ON and the magnetic field is directed away from the plate, electrons are evenly distributed across the plate. When the rotor directs the field toward the plate, the electrons are redistributed unevenly across the front and back of the plate. The uneven distribution causes a voltage to be produced across the plate. The VSS produces a frequency signal that is proportional to vehicle speed. The ECM converts the VSS signal to vehicle speed, displayed on the scan tool in miles per hour and kilometers per hour. The ECM also uses the VSS signal to generate the 4,000 pulses per mile vehicle speed signal used by the instrument cluster.

When the ECM detects a very low vehicle speed, while the vehicle is in motion, DTC P0502 sets. DTC P0502 is a type B DTC.

Conditions for Running the DTC

- Engine speed is 1,900-3,800 RPM.
- The throttle position angle is less than 1 percent.
- MAP sensor is 70-80 kPa.

Conditions for Setting the DTC

The vehicle speed sensor indicates a speed of less than 5 km/h (3 mph) for a total of 3 seconds.

Action Taken When the DTC Sets

- The ECM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The ECM disables Cruise Control.
- The ECM records the operating conditions at the time when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
- The ECM stores P0502 in PCM history.

Conditions for Clearing the MIL/DTC

- The ECM turns OFF the MIL during the third consecutive trip in which the diagnostic runs and passes.
- The ECM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the ECM.
- The ECM clears the DTC from ECM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
- A scan tool can clear the MIL/DTC.