DTC 72

DTC 72:

Vehicle Speed Sensor Circuit:

CIRCUIT DESCRIPTION
The vehicle speed sensor (VSS) circuit consists of a magnetic induction type sensor and wiring. Gear teeth pressed on the output shaft induce an alternating current in the sensor.

The Powertrain Control Module (PCM) compensates for various axle ratios and converts the signal into a square wave for use by the speedometer, cruise control, antilock brakes, and Traction Control (TC) system.


DTC 72 WILL SET WHEN:
Not in P/N, transmission output speed changes greater than 1000 RPM, or in P/N, transmission output speed change greater than 2048 RPM. No DTC 28, and engine speed greater than 200 RPM. All conditions met for 2 seconds.


ACTION TAKEN (PCM will default to):
A delayed (soft) landing to third gear. DTC 72 will be stored in the PCM memory but will not turn "ON" the Malfunction Indicator Lamp (MIL).


DTC 72 WILL CLEAR WHEN:
The fault condition(s) no longer exist, and the ignition switch is cycled "OFF" then "ON."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. The TC system must be disabled when performing this step. Whenever the ignition key is cycled to the "OFF" position and then cycled back "ON," the TC system will default "ON."
2. An intermittent connection at the VSS or PCM may cause a DTC 72 to set. Inspect the harness and all related connectors. Check for damaged or pushed out terminals.
3. Be sure harness is routed away from hot exhaust components.

DIAGNOSTIC AIDS
^ DTC 24 will set when no vehicle speed is detected at start off.
^ DTC 72 will set when vehicle speed has been detected and is lost.