DTC 24

Fig. 018a Chart - Code 24:

Fig. 019 - Wiring Diagram for Code 24 Vehicle Speed Sensor. VIN Z:

CODE 24

VEHICLE SPEED SENSOR (VSS)

4.3L ENGINE

5.0L ENGINE

FUEL INJECTION (TBI)



The ECM supplies a current limited 12 volt signal on CKT 437. The VSS located in the I.P. cluster will sense the speedometer rotating element and furnish this information to the buffer as a "Pulsed" signal, 2 per cable revolutions of 2002 per mile.
The buffer assembly will switch CKT 437 to ground for each pulse received. The ECM uses the time between pulses to determine vehicle speed.
Code 24 is set by the following:
1. Code 24 will set when vehicle speed is 0 MPH and;
a. CKT 437 voltage is constant. No rise and fall of voltage for about 5 seconds.
b. Engine speed between 1500 and 4400 RPM.
c. Low MAP (High Vacuum) indicating an engine decel.
d. TPS is less than 2% (closed throttle).

Disregard a code 24 that sets when the drive wheels are not turning


2. 8 to 12 volts, at the instrument panel connector, shows CKT 437 is open between the VSS and I.P. connector, or the VSS is bad. 1 volt or less at the I.P. connector indicates a short to ground in CKT 437. If the voltage reads above 10 volts after disconnecting the I.P. connector the VSS is bad. If the voltage remains below 8 volts, CKT 437 is grounded. If CKT 437 wire is not shorted to ground there is a faulty connection at the ECM or the ECM is bad.


DIAGNOSTIC AIDS

"SCAN" should indicate a vehicle speed when the drive wheels are turning.
A bad or misadjusted park/neutral switch can set a false code 24. Check for proper signal in drive with a scan tool. For P/N switch diagnosis see C CHARTS, chart C-1A.
If all checks are OK see DIAGNOSIS BY SYMPTOMS.