P0503

DTC P0503

Schematic:

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 PCM. The PCM converts the AC voltage into a digital signal. The PCM uses vehicle speed to determine shift timing, torque converter clutch apply and release and gear ratio.
If the PCM detects a loss of vehicle speed while the vehicle is in motion, then DTC P0503 sets. DTC P0503 is a type B DTC.

Conditions for Running the DTC
- No AT ISS DTCs P0716 or P0717.
- No IMS DTCs P1820, P1822, P1823, or P1825.
- No 1-2 shift solenoid valve electrical DTC P1843.
- The engine run time is greater than 5 seconds.
- The transmission is not in PARK or NEUTRAL.
- The time since the gear select lever change is greater than 6 seconds.
- The transmission input shaft speed has not changed by 500 RPM or greater for at least 4.8 seconds.
- LD8: The transmission output shaft speed is greater than 1,244 RPM and has not increased by 500 RPM or greater for at least 2 seconds.
- L37: The transmission output shaft speed is greater than 1,484 RPM and has not increased by 500 RPM or greater for at least 2 seconds.

Conditions for Setting the DTC
- LD8: The transmission output shaft speed drops 1,089 RPM or greater for at least 1 second.
- L37: The transmission output shaft speed drops 1,299 RPM or greater for at least 1 second.

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 adapt 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 P0503 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

Steps 1-8:

Steps 9-15:

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 1,950 ohms which would indicate an open in the high signal circuit, the low signal circuit or the VSS.