Powertrain Controls - ECM/PCM

Code 24:

VSS Circuit:

CIRCUIT DESCRIPTION:

Vehicle speed information is provided to the PCM by the Vehicle Speed Sensor (VSS), in the transaxle. The AC 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 scan tool. 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.

Code E024 will set if vehicle speed signal equals less than 3 mph when:

^ Engine is running.
^ No code 31 is set.
^ When the vehicle is in 4th gear.
^ Engine speed is greater than 3000 rpm.
^ All conditions met for 2.0 seconds.
^ Vehicle speed goes from greater than 18.0 to 0 mph in less than 2.0 seconds, brake not applied.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. The VSS signal generator only produces a signal if drive wheels are turning greater than 3.0 mph.

2. Before replacing the PCM, check the MEM-CAL for correct application.

DIAGNOSTIC AIDS:

The on-board deagnostic/Tech 1 display should indicate a vehicle speed whenever the drive wheels are turning greater than 3.0 mph. Check CKT 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.