P0501

DTC P0501 Vehicle Speed Sensor Circuit






Circuit Description

The speed sensor circuit consists of a magnetic induction type sensor, a Digital Ratio Adaptor (DRA) and wiring. Geared teeth pressed on the output shaft induce an alternating current in the sensor. This A/C signal is transmitted to the DRA. The DRA compensates for various axle ratios and converts the signal into a digital signal for use by the speedometer, cruise control, and the PCM. The DRA sends two different signal to the PCM. Circuit 565 sends a signal of 40 pulses per revolution of the output shaft to the PCM. This signal is used to control shift points, line pressure, TCC and diagnostic codes. Circuit 223 sends a signal of 4000 pulses per mile to the PCM. This signal is used to control engine operating functions, cruise control and DTCs. When DTC PO501 or P0723 is set, second gear only at a maximum line pressure will occur. This is a type D DTC.

Conditions for Setting the DTC

^ Vehicle speed greater than 20 m.p.h.
^ Four wheel low not selected.
^ VSS buffer calculated speed is less than half the transmission calculated speed.
^ VSS buffer calculated speed is greater than transmission calculated speed by 20 m.p.h.
^ All conditions met for 2 seconds.

Action Taken When the DTC Sets

No cruise control.

Conditions for Clearing the MIL/DTC

^ A History DTC will clear when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle).
^ Use of a scan.

Diagnostic Aids

Check connections at VSS buffer and PCM. Refer to 4L80E Diagnostic Diagnostic Trouble Codes, Section 10 if DTC P0722 or DTC P0723 is also set.

Test Description

Number(s) below refer to the number(s) on the diagnostic table.

3. This tests for B+ at VSS buffer.

4. This tests for proper ground path for vehicle speed sensor signal buffer.