Tremec 6-Speed Manual Transmission
DTC P0502
Circuit Description
Vehicle speed information is provided to the engine control module (ECM) by the vehicle speed sensor (VSS). The VSS is a permanent magnet generator that is mounted on the transmission and produces a pulsing voltage. The AC voltage amplitude and frequency increases with vehicle speed. The ECM converts the pulsing voltage into km/h (mph). The ECM supplies the necessary signal to the instrument panel for speedometer, odometer operation, and to the cruise control module. The ECM also supplies the signal to the body control module (BCM), and the electronic suspension control module, if equipped.
If the ECM detects no vehicle speed for 50 seconds, 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 MAP sensor DTCs P0106 or P0107.
* No ECT sensor DTCs P0117 or P0118.
* No idle control system DTC P0506 or P0507.
* No TP sensor DTCs P0120 or P0220.
* The ECT is 35°C (95°F) or greater.
* The engine speed is greater than 1,000 RPM.
* The TP angle is 5-100 percent.
* The MAP is 40-100 kPa when the A/C is OFF.
* The MAP is 45-100 kPa when the A/C is ON.
* All conditions are met for more than 2 seconds.
Conditions for Setting the DTC
The ECM detects no vehicle speed (0 km/h (0 mph)) for 50 seconds.
Action Taken When the DTC Sets
* The ECM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
* The ECM disables Cruise Control.
* The ECM commands the coolant fan ON.
* The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
* The ECM stores DTC P0502 in ECM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the MIL/DTC
* The ECM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
* A scan tool can clear the MIL/DTC.
* The ECM clears the DTC from ECM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
* The ECM 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 ECM.
4. This step tests the VSS circuit for correct resistance.
