Automatic Transmission

Diagnostic Chart:

Wiring Diagram:

Circuit Description

Vehicle speed information is provided to the Powertrain Control Module (PCM) by the Vehicle Speed Sensor (VSS). The VSS is a magnet generator that is mounted in the transaxle and produces a pulsating AC voltage. The AC voltage level and the number of pulses increase with vehicle speed.


Conditions for Setting the DTC

No vehicle speed sensor signal, in fuel shut off mode for more than 4 seconds.


Action Taken When the DTC Sets

^ The Malfunction Indicator Lamp (MIL) will illuminate.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

^ The PCM will enter the Fail-Safe Function and stop Idle Speed (ISC) control.


Conditions for Clearing the MIL/DTC

^ The MIL will turn OFF after three consecutively passing cycles without a fault present.

^ A History DTC will clear after 40 consecutive warm-up cycles without a fault.

^ DTCs can be cleared by using a scan tool or by disconnecting the PCM battery teed.


Diagnostic Aids

Check for any of the following conditions:

^ A poor connection at the PCM. Inspect the harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal to wire connection.

^ A damaged wiring harness. Inspect the wiring harness for damage and repair as necessary.

^ A faulty speedometer cable. If the speedometer cable is binding, a false DTC P0500 can be set. Make sure that the speedometer cable is free from any restrictions and that it has a secure connection to the I/P cluster assembly.

If a DTC P0500 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

If any wiring repairs need to be made, Refer to Repair Procedures in Electrical Diagrams.


Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Determine if fault is present.

3. Review Freeze Frame data to determine when the DTC set. Always record this information.

4. Measure the resistance of the VSS.