Powertrain Controls - ECM/PCM

DTC 75 Charts:

Vehicle Speed Sensor Circuits:

CIRCUIT DESCRIPTION
The Transaxle Input Speed Sensor (TISS) and the transaxle Vehicle Speed Sensor (VSS) consists of a permanent magnet surrounded by a coil of wire. These sensors create a magnetic field, as the rotor teeth pass through the magnetic field an (AC) voltage is generated. This analog signal is sent to the Powertrain Control Module (PCM) and then changed to a digital signal. These signals are then used by the PCM to control outputs within the control program.

DTC 75 WILL SET WHEN
- No DTCs 21, 22, 27, 56, 90.
- TCC brake switch not applied.
- Traction control not active.
- Two seconds since key "ON."
- Throttle angle 15.7 degrees or greater
- Engine speed 500 RPM or greater.
- Vehicle speed changes 4 mph or more in 12.5 milliseconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
- With a current DTC 75 set, the PCM will illuminate the Malfunction Indicator Lamp (MIL) (Service Engine Soon).
- No Torque Converter Clutch (TCC).
- PCM freezes transaxle in current gear.
- If test and failure are true 10 times within 10 seconds, DTC 75 will remain current for the ignition cycle.

DTC 75 WILL CLEAR WHEN
The fault no longer exists and the ignition switch is cycled "OFF" and "ON."

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

1. This test checks for a Vehicle Speed Sensor (VSS) signal.
2. This test checks for a calibration error.
3. This test checks the VSS wires and connections to the PCM.

DIAGNOSTIC AIDS
This DTC operates on the fact that a substantial change in vehicle speed must always be followed by a substantial change in transaxle input speed. So if a sudden change in vehicle speed is noticed without any accompanying change in turbine speed, then a vehicle speed error condition has occurred.