DTC 24

Vehicle Speed Sensor (VSS) And Park/Neutral Switch Circuit Diagram:

CIRCUIT DESCRIPTION:
Vehicle speed information is provided to the PCM by the vehicle speed sensor in the transaxle. The sensor consists of a permanent magnet, rotating in a stationary induction coil, which generates an A/C voltage signal. The sensor generates 4000 pulses per mile. As the vehicle speed increases, so does the frequency of the signal. The PCM counts the number of pulses in a given time and calculates the vehicle speed. The function of the VSS buffer, used in past models years has been incorporated into the PCM. The PCM supplies the necessary signal for the instrument panel for operating the speedometer and the odometer.

NOTE: The sensor will only produce a signal if the drive wheels are turning faster than 3 mph.

Code 24 will set when:

^ Engine is running.
^ Vehicle speed sensor signal indicates less than 3 mph.
^ MAP sensor signal indicates less than 30kPa manifold absolute pressure.
^ Engine speed is between 2200 and 4400 rpm.
^ TPS signal indicates less than 10% throttle opening.
^ Transmission range switches indicate transmission in a drive gear (not in park or neutral.)
^ Codes 21, 22, 33, or 34 not present.
^ All conditions exist for 3 seconds.

TEST DESCRIPTION

Code 24 Diagnostic Chart:

Numbers below refer to circled numbers on the diagnostic chart.
1. The VSS signal generator only produces a signal if the drive wheels are turning greater than 3 mph.
2. If circuits 400, 401, and 389 are OK, and the speedometer works, then Code 24 is due to an incorrect MEM-CAL, faulty MEM-CAL, or faulty PCM. Before replacing the PCM, 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.
^ A faulty or mis-adjusted park/neutral switch can cause a false Code 24. Use a "SCAN" tool to check for proper signal when in overdrive. Chart C-1A Park/Neutral Switch Diagnosis for park/neutral switch diagnosis.