Engine Control System
CODE 24 VEHICLE SPEED SENSOR (VSS) CIRCUITCode Chart 24:
Vehicle Speed Sensor Circuit:
CIRCUIT DESCRIPTION:
The Vehicle Speed Sensor (VSS), which is located in the instrument panel is a reed switch type. The ECM provides battery voltage to the switch which will toggle the voltage high and low. This pulsed signal to the ECM is used by the ECM to determine mph/kph.
TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.
1. Code 24 will set if vehicle speed equals 0 mph when:
^ Engine speed is between 1800 and 4400 rpm.
^ TPS is at 0% (closed throttle).
^ Low load condition (low MAP voltage, high manifold vacuum).
^ Not in Park or Neutral.
^ All conditions met for 3 seconds.
These conditions are met during a road load deceleration. Disregard Code 24 that sets when drive wheels are not turning.
DIAGNOSTIC AIDS:
Scan should indicate a vehicle speed whenever the drive wheels are turning greater than 3 mph. Check the WHT wire for proper connection to be sure they are clean and tight and the harness is routed correctly. Testing and Inspection (A/T) A faulty or misadjusted Park/Neutral switch can result in a false Code 24. Use a Scan tool and check for proper signal while in drive. For P/N switch check, Chart C-1A Park/Neutral Switch Diagnosis