P0502

DTC P0501/P0502:

Vehicle Speed Sensor Wiring Schematic:

CIRCUIT DESCRIPTION
Vehicle speed information is provided to the Powertrain Control Module (PCM) by the Vehicle Speed Sensor (VSS) in the transaxle. The voltage level and the number of pulses increases with vehicle speed. The PCM converts the pulsing voltage to mph, and the mph can be displayed with a Tech 1.

The function of the VSS buffer, used in past model years, has been incorporated into the PCM. The PCM supplies the necessary signal for the instrument panel (4004 pulses per mile) for operating the speedometer and the odometer.

DIAGNOSTIC TROUBLE CODE (DTC) PO501 WILL SET WHEN
^ Engine is running.
^ No DTC P0703.
^ Transmission is out of park or neutral for more than 4 seconds.
^ Vehicle speed is greater than 18 mph.
^ Brake not applied.
^ All conditions met for 2 seconds.

DIAGNOSTIC TROUBLE CODE (DTC) P0502 WILL SET WHEN
^ Vehicle speed goes from less than 3 to 0 mph in less than 2 seconds, brake not applied.
^ Engine is running.
^ Engine speed is greater than 3000 RPM.
^ Transmission is out of park or neutral for more than 4 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
Cruise control operation will not be allowed with DTC P0501 or P0502 set. Also, DTC will remain set for rest of that ignition cycle and the PCM will command only 2nd and 3rd gear based on RPM and Throttle Position (TP) Sensor. Torque Converter Clutch (TCC) will not be allowed to engage. Additionally, the cluster speedometer may be inoperative. The Malfunction Indicator Lamp (MIL) (Service Engine Soon) will be illuminated.

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

1. The VSS signal generator only produces a signal if drive wheels are turning greater then 3 mph.
2. Before replacing the PCM, check the PROM for correct application.

DIAGNOSTIC AIDS
Tech 1 should indicate a vehicle speed whenever the vehicle is moving greater than 3 mph.

DTC P0502 indicates an intermittent problem and may not set immediately or under all conditions. Check CKTs 400 and 401 for proper connections to be sure they are clean and tight and the harness is routed correctly.
Refer to "Intermittents," in "Diagnosis by Symptom". - Intermittent Malfunctions