Aisin AR5 - Manual Transmission
DTC P0502
Circuit Description
The vehicle speed sensor (VSS) assembly provides vehicle speed information to the powertrain control module (PCM). The VSS assembly is a permanent magnet generator. The VSS produces alternating current (AC) as the rotor teeth on the output shaft of the transmission, 2WD, or transfer case, 4WD, pass through the magnetic field of the sensor. The frequency and amplitude of the AC waveform increase as vehicle speed increases.
If the PCM detects no vehicle speed for a specified length of time, while other sensors indicate that the vehicle is moving, DTC P0502 sets. DTC P0502 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Voltage
Conditions for Running the DTC
* No VSS DTC P0503.
* No TP sensor DTCs P0120 or P0121.
* The TP sensor angle is 12 percent or more.
* The engine speed is 1,000-6,800 RPM for 8 seconds.
* The system voltage is 10-18 V.
* Engine torque is 40-300 N.m (30-221 lb ft).
Conditions for Setting the DTC
The transmission output speed is 100 RPM or less for 3 seconds.
Action Taken When the DTC Sets
* The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
* The PCM disables Cruise Control.
* The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
* The PCM stores DTC P0502 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the MIL/DTC
* The PCM turns OFF the MIL during the third consecutive ignition cycles in which the diagnostic test runs and passes.
* A scan tool can clear the MIL/DTC.
* The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
* The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes.
Diagnostic Aids
Ensure the VSS is correctly torqued to the transmission housing.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step tests the ability of the VSS to produce an AC voltage. This step also verifies the integrity of the wiring to the PCM.
4. This step tests the VSS circuit for correct resistance.
