DTC 24

Code 24 - Vehicle Speed Sensor (VSS):

Wiring Diagram For Code 24 - Vehicle Speed Sensor (VSS):

CODE 24 - VEHICLE SPEED SENSOR (VSS)




Circuit Description:

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:

^ CKT 437 voltage is constant. No rise and fall of voltage for about 5 seconds.
^ Engine speed between 1500 and 4400 RPM.
^ Park/Neutral switch indicates transmission selector is in drive range.
^ Low MAP (High Vacuum) indicating an engine decel. Loss of VSS will affect:
^ Transmission Converter Clutch
^ Idle Air Control



Test Description:

1. With the wheels turning, the pulsing action wilt result in a varying voltage. The variation will be greater at low wheel speeds to an average of 4-6 volts at about 20 mph (32 Km/h).

2. A voltage of less than 1 volt indicates that the CKT 437 wire is shorted to ground. Disconnect CKT 437 at the vehicle speed sensor. If voltage now reads above 10 volts, the Vehicle Speed Sensor is faulty. If voltage remains less than 10 volt, then CKT 437 wire is grounded. If 437 is not grounded, check for a faulty ECM connector or ECM.

3. A steady 8-12 volts indicates CKT 437 is open or a faulty vehicle speed sensor.

4. This is a normal voltage condition.

5. If "SCAN" displays vehicle speed, check park/neutral switch Chart C-1A on vehicle with auto. trans. If switch is OK, check for intermittents.