Transmission Code

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The Vehicle Speed Sensor Assembly (VSS Assy.) provides vehicle speed information to the Powertrain Control Module (PCM). The VSS Assy. is a Permanent Magnet (PM) generator. The PM generator produces a pulsing Idle Air Control (IAC) voltage as rotor teeth on the transmission output shaft pass through the sensor's magnetic field. The IAC voltage level and the number of pulses increase as the speed of the vehicle increases. The output voltage varies from a minimum of 0.5 volts IAC at 100 RPM to more than 100 volts at 8000 RPM. The PCM converts the pulsing voltage to vehicle speed. The PCM uses the vehicle speed signal to determine shift timing and Torque Converter Clutch (TCC) scheduling.

When the PCM detects a low vehicle speed when there is a high engine speed in a drive gear range, then DTC P0502 sets. DTC P0502 is a type B DTC.

CONDITIONS FOR SETTING THE DTC

DTC P0502 sets if the following conditions occur two consecutive times:

^ No Manifold Absolute Pressure (MAP) Sensor DTCs P0107 or P0108.

^ No Throttle Position (TP) Sensor DTCs P0122 or P0123.

^ No Transmission Fluid Pressure (TFP) Val. Position Sw. DTC P1810.

^ The transmission is not in Park or Neutral.

^ The TP angle is greater than 20%.

^ The engine speed is greater than 3200 RPM.

^ The engine vacuum is 112-176 kPa.

^ The transmission output speed is less than 150 RPM.

^ All conditions met for 3 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

^ The PCM commands second gear only.

^ The PCM commands maximum line pressure.

^ The PCM inhibits TCC engagement.

^ The PCM freezes shift adapts from being updated.

^ DTC P0502 stores in PCM history.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The PCM turns OFF the MIL after three consecutive trips without a failure reported.

^ A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

DIAGNOSTIC AIDS

^ Inspect the wiring at the PCM, the Vehicle Speed Sensor (VSS) connector and all other circuit connecting points for the following conditions:

- A bent terminal.

- A backed out terminal.

- A damaged terminal.

- Poor terminal tension.

- A chafed wire.

- A broken wire inside the insulation.

- Moisture intrusion.

- Corrosion.

^ When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

TEST DESCRIPTION

The numbers below refer to the step numbers on the diagnostic table.

3. This step tests the VSS Assy. circuit.

5. This step tests the integrity of the VSS Assy.