P0503
Circuit Description with 4T80-E Automatic TransaxleSchematic:
The Vehicle Speed Sensor (VSS) is a Permanent Magnet (PM) 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 (TCC) apply and release and gear ratio. VSS voltage will vary from 0.5 volts AC at 100 RPM to more than 100 volts AC at 8000 RPM. VSS resistance value is between 1300-1950 ohms.
If the PCM detects a large change in vehicle speed, 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 engine is not in fuel cut off.
^ The transmission is not in PARK or NEUTRAL.
^ The time since the gear select lever change is greater than 6 seconds.
^ The transmission output shaft speed is greater than 1484 RPM and does not increase by greater than 500 RPM for 2 seconds.
CONDITIONS FOR SETTING THE DTC
The transmission output shaft speed drops greater than 1299 RPM for greater than 1 second and the input shaft speed has not changed by greater than 500 RPM for greater than 4.8 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 adapt functions.
^ The PCM calculates vehicle speed from the automatic transmission input (shaft) speed sensor and commanded gear.
^ 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 fault no longer exists and/or the ignition switch is OFF long enough in order to power down the PCM.
DIAGNOSTIC AIDS
^ Inspect the connectors at the PCM, the VSS and all other circuit connecting points for an intermiffent condition. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Diagrams.
^ Inspect for Electromagnetic Interference (EMI) induced on the signal and ground circuits by a misrouted wiring harness along spark plug wires.
^ Ensure that the VSS is tightened securely into the transmission case extension.
TEST DESCRIPTION
Steps 1 - 6:
Steps 7 - 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 1950 ohms which would indicate a possible open in the signal circuit or the ground circuit.