With PFI

Code 24 - Vehicle Speed Sensor (VSS) Circuit:

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

CODE 24 - VEHICLE SPEED SENSOR (VSS) CIRCUIT

Circuit Description:


The ECM applies and monitors 12 volts on CKT 437. CKT 437 connects to the vehicle speed sensor which alternately grounds CKT 437 when drive wheels are turning. This pulsing action takes place about 2000 times per mile and the ECM will calculate vehicle speed based on the time between "pulses." Disregard a Code 24 set when drive wheels are not turning.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. This test monitors the ECM voltage on CKT 437. With the wheels turning, the pulsing action will 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 at the ECM connector 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 volts, then CKT 437 wire is grounded. Be sure cruise control is "OFF" or disconnected.


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


4. This is normal voltage condition and indicates a possible intermittent condition. See "Intermittents," in Diagnosis By Symptoms - No Trouble Codes Stored.


5. If "Scan" displays vehicle speed, check park/neutral switch CHART C-1A on vehicle with auto trans. If switch is OK, see "Intermittents," in Diagnosis By Symptoms - No Trouble Codes Stored.