Powertrain Controls - ECM/PCM

Code 24 Chart:

Code 24 Wiring Diagram:

CIRCUIT DESCRIPTION
Vehicle speed information is provided to the Electronic Control Module (ECM) by the Vehicle speed Sensor (VSS), in the transaxle. The A/C voltage level and the number of pulses increases with vehicle speed. The ECM 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 models years has been incorporated in the ECM. The ECM supplies the necessary signal for the instrument panel (4004 pulses per mile) for operating the speedometer and the odometer.


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

1. Code 24 will set if vehicle speed signal equals less than 3 mph when:
^ Engine is running
^ No Code 29 or 31
^ When the vehicle is in 4th gear
^ All conditions met for 40 seconds

2. Before replacing the ECM, check the Mem-Cal for correct application.

DIAGNOSTIC AIDS
Scan should indicate a vehicle speed whenever the drive wheels are turning greater than 3 mph. Check circuit 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.