P0502

DTC P0502





Circuit Description
The vehicle speed sensor (VSS) is a permanent magnet generator attached to the transmission case. The final drive assembly has a toothed wheel, VSS rotor. As the final drive assembly rotates, an AC voltage is induced and transmitted to the powertrain control module (PCM). The PCM converts the AC voltage into a digital signal. The PCM uses the vehicle speed to determine shift timing, torque converter clutch apply and release, and gear ratio.

If the PCM detects a low vehicle speed and a high transmission input shaft 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 MAF DTCs P0101, P0102 or P0103.
^ No MAP DTCs P0106, P0107 or P0108.
^ No TP DTCs P0121, P0122 or P0123.
^ No VSS DTC P0503.
^ No AT ISS DTCs P0716 or P0717.
^ No IMS DTCs P1820, P1822, P1823 or P1825.
^ The engine run time is greater than 5 seconds.
^ The transmission is not in PARK or NEUTRAL.
^ The TP angle is 12 percent or greater.
^ The engine torque is 60 - 395 Nm (44 - 291 ft. lbs.).
^ The transmission input shaft speed is 1,000 - 5,000 RPM.
^ Trans. Temp. is 0°C (32°F) or greater.
^ TCC slip speed is greater than -5 RPM.

Conditions for Setting the DTC
LD8: The transmission output shaft speed is 280 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 commands maximum line pressure.
^ The PCM freezes transmission adaptive functions.
^ The PCM calculates vehicle speed from the automatic transmission input, shaft, speed sensor and commanded gear.
^ The PCM applies the TCC in 3rd gear when in Hot Mode.
^ 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.
2. This step tests for DTCs and for a vehicle speed signal. It is important to record Freeze Frame and Failure Record information before proceeding further.
5. This step tests for a resistance value greater than 1,911 ohms which would indicate an open in the high signal circuit, the low signal circuit or the VSS.