4L60-E / 4L65-E Automatic Transmission

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The Vehicle Speed Sensor (VSS) assembly provides vehicle speed information to the Vehicle Control Module (VCM). The VSS assembly is a Permanent Magnet (PM) generator. The PM generator produces a pulsing AC voltage as rotor teeth on the transmission output shaft pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The VCM converts the pulsing voltage to vehicle speed. The VCM uses the vehicle speed signal to determine shift timing and Torque Converter Clutch (TCC) scheduling.

When the VCM detects an unrealistically large drop in vehicle speed, then DTC P0503 sets. DTC P0503 is a type B DTC.

CONDITIONS FOR RUNNING THE DTC
^ No TFP manual valve position switch DTC P1810.
^ The engine speed is greater than 450 RPM for 5 seconds.
^ The engine is not in fuel cutoff.
^ The time since the last gear range change is greater than 6 seconds.
^ The transmission output speed rise does not exceed 600 RPM within 6 seconds.

CONDITIONS FOR SETTING THE DTC
The transmission output speed drops by greater than 1300 RPM for 3 seconds when the transmission is not in PARK or NEUTRAL.

ACTION TAKEN WHEN THE DTC SETS
^ The VCM illuminates the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
^ The VCM commands a soft landing to second gear, below 2500 RPM.
^ The VCM commands maximum line pressure.
^ The VCM inhibits TCC engagement.
^ The VCM inhibits fourth gear if the transmission is in hot mode.
^ The VCM freezes shift adapts from being updated.
^ The VCM records the operating conditions when the Conditions for Setting the DTC are met. The VCM stores this information as Freeze Frame and Failure Records.
^ The VCM stores DTC P0503 in VCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The VCM 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 VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
^ The VCM 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 VCM.

DIAGNOSTIC AIDS
^ Inspect the connectors at the VCM the VSS assembly and all other circuit connecting points for an intermittent 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 ABS DTCs. A faulty ABS condition may contribute to setting DTC P0503.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
3. This step tests the VSS assembly circuit.
4. This step tests the integrity of the VSS assembly.
6. This step tests the 5-volt and ground circuits of the VCM.