With 3 Speed Automatic

Circuit Description
The vehicle speed sensor (VSS) assembly provides vehicle speed information to the powertrain control module (PCM). The VSS assembly is a permanent magnet (PM) generator. The PM generator produces a pulsing AC voltage as the speed sensor rotor teeth on the transmission governor assembly pass through the sensor's magnetic field. The AC voltage level and the number of pulses increases as the speed of the vehicle increases. The output voltage varies from a minimum of 0.5 volts AC at 25 RPM to more than 100 volts at 200 RPM. The PCM convents the pulsing voltage to vehicle speed. The PCM uses the vehicle speed signal to calculate torque converter clutch (TCC) scheduling. When the PCM detects a low vehicle speed and there is a high engine speed in a drive range, then DTC P0503 sets. DTC P0503 is a type B DTC.

Conditions for Running the DTC
^ Engine is running.
^ Transmission output speed is greater than 500 RPM.
^ Last gear range change has been more than 6 seconds.

Conditions for Setting the DTC
DTC P0503 sets during the second consecutive trip in which the following condition occurs:
Transmission output speed drops more than 1200 RPM in a drive range for 4 seconds.

Action Taken When the DTC Sets
^ The PCM illuminates the malfunction indicator lamp (MIL).
^ TCC will not apply.
^ DTC P0503 stores in PCM history.

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 clears the DTC from PCM history.
^ The PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related fault occurring.

Diagnostic Aids
^ Inspect for electromagnetic interferences (EMI) induced on circuit 400 and circuit 401 by an improperly routed harness.
^ Inspect the wiring at the PCM, the vehicle speed sensor (VSS) assembly connector and all other circuit connecting points for the following conditions:
- A backed out terminal.
- A damaged terminal.
- Reduced 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.
2. This step tests for a vehicle speed signal.
3. This step checks for the VSS assembly ability to produce an AC voltage.
4. This step checks for correct circuit resistance.
7. When the VSS assembly is disconnected, the circuit resistance should be infinite.
10. This step checks for improper voltage in the circuit.
15. This step inspects for possible mechanical problems.
17. Replace the PCM only after you have completed the preceding diagnostic steps.