P0502
DTC P0502 (3.8L)
Circuit Description
The vehicle speed sensor (VSS) system is a pulse generator consisting of a speed sensor assembly, located in the case extension, and a toothed vehicle speed sensor reluctor wheel, which is pressed onto the final drive carrier assembly. As the vehicle drives forward, the vehicle speed sensor reluctor wheel rotates. This rotation produces a variable AC signal in the pickup coil that is proportional to vehicle speed. The powertrain control module (PCM) uses this signal in order to calculate vehicle speed, shift timing and gear ratios.
If the PCM detects a low vehicle speed with a high engine speed while in a drive range, then 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 DTC P0107 or P0108.
* No ISS DTC P0716 or P0717.
* The engine is running for greater than 5 seconds and not in fuel cut-off.
* The TP indicated angle is 12 percent or greater.
* The engine torque is 68-400 N.m (50-300 lb ft).
* The input shaft speed is 1,500 RPM or greater.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The TCC slip speed is 0 RPM or greater.
Conditions for Setting the DTC
The output shaft speed is 150 RPM or less for 5 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 freezes transmission adaptive functions.
* The PCM calculates vehicle speed from the input speed sensor for shift timing.
* 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 trip 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 ignition switch is OFF long enough in order to power down the PCM.
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.
Step 1 - Step 6:
Step 7 - Step 14:
