P0502

Code P0502/P0502, Vehicle Speed Sensor (VSS) Circuit:

Vehicle Speed Sensor (VSS) Circuit:

CIRCUIT DESCRIPTION
Vehicle speed information is provided to the 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 odometer.

DTC P0501 WILL SET WHEN:
^ Vehicle speed goes from greater than 18 to zero mph in less than 2 seconds, brake not applied.

DTC P0502 WILL SET WHEN:
^ Engine is running.
^ No DTC P0705.
^ Transmission is out of park or neutral for more than 4 seconds.
^ Engine speed is greater than 3250 RPM.
^ Vehicle speed is less than 3 mph.
^ All conditions met for 2 seconds.

ACTION TAKEN (PCM will default to):
Cruise control operation will not be allowed with DTC P0501 or P0502 set. Also, the transaxle will be forced into 3rd gear with a 3-2 downshift available; TCC will not be allowed to engage. Additionally, the cluster speedometer may be inoperative. The MIL (Service Engine Soon) will be illuminated.

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 P0501 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 "DIAGNOSIS BY SYMPTOM/INTERMITTENTS. - Intermittent Malfunctions