P0720

DTC P0720 Output Speed Sensor Circuit:

Output Speed Sensor Circuit:

CIRCUIT DESCRIPTION

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


DTC DETECTING CONDITIONS

With 4L switch open, no VSS (Transmission) signal is received while 2000 pulses of VSS (Speedometer) signal is received during 2 driving cycles.


ACTION TAKEN

A DTC P0720 is stored and both the "OD/OFF" and "SERVICE ENGINE SOON" indicators are turned "ON."

DTC CHART TEST DESCRIPTION

Numbers below refer to circled numbers on the diagnostic chart.

1. Checks for proper resistance values.

2. Checks for a faulty VSS (Transmission).

3. Checks for an open in ORN wire.

4. Checks for an open in WHT wire.

5. Determines whether this condition is intermittent and not due to a defective TCM.

6. Checks for proper voltage output of the VSS (Transmission).


DIAGNOSTIC AIDS

An intermittent condition may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Inspect the TCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and for poor terminal-to-wire connections. In addition, carefully check the VSS (Transmission) shielding and shield ground for breaks, cuts or opens.