P0720

Diagnostic Chart 1 Of 2:

Diagnostic Chart 2 Of 2:

Schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) receives an AC voltage input from the Vehicle Speed Sensor (VSS) when the drive wheels are rotating. Because the frequency of the AC voltage signal increases with the wheel speed, the PCM can calculate vehicle speed from the frequency of the AC signal. The PCM uses this information in order to determine shift points.

CONDITIONS FOR SETTING THE DTC
DTC P0720 will set if the following conditions are met:
^ No VSS signal is inputted while the vehicle is running in the Drive (D) gear or in the Second (2) gear.
^ One driving cycle detection logic.

ACTION TAKEN WHEN THE DTC SETS
A DTC P0720 is stored, and the Malfunction Indicator Lamp (MIL) is turned ON.

DIAGNOSTIC AIDS
Check for the following conditions:
^ An open VSS or A shorted VSS
^ Faulty electrical circuits between the VSS and the PCM
^ A faulty PCM

An intermittent may be caused by the following conditions: a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
^ A poor connection
^ Rubbed-through wire insulation
^ A broken wire inside the insulation

Inspect the PCM harness connectors for the following conditions:
^ Backed out terminals
^ Incorrect mating
^ Broken locks
^ Incorrectly formed terminals or damaged terminals
^ Poor terminal-to-wire connections

Perform the following steps if DTC P0720 cannot be duplicated:
^ Read the information in the freeze frame data.
^ Use the data in order to determine the vehicle operating conditions when the DTC was set.

Inspect the wiring. If any wiring repairs are necessary, Refer to Wiring Repairs in Diagrams.

DTC CONFIRMATION PROCEDURE
1. Turn the ignition switch to the LOCK position.
2. Connect the scan tool to Data Link Connector (DLC).
3. Turn the ignition switch to ON.
4. Use the scan tool in order to clear the following items from the PCM memory:
^ The DTC
^ The pending DTC
^ The freeze frame data
5. Start the engine.
6. Operate the vehicle in (2) Range. Obtain a engine speed of at least 3500 RPM for at least 10 seconds.
7. Stop the vehicle.
8. Use the scan tool in order to inspect for DTC P0720.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and to store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information is stored in the scan tool for later reference.
3. This step inspects for internal resistance of the VSS.
4. This step inspects for a faulty VSS.
5. This step inspects for an open in the LT GRN wire.
6. This step inspects for an open in the PPL wire.
7. This step inspects for a faulty PCM.
8. This step inspects the voltage output of the VSS.