Code 24: Vehicle Speed Sensor (3.1L): Notes

ECM applies and monitors a 12-volt signal on circuit No. 437 to Vehicle Speed Sensor (VSS). VSS alternately grounds and opens circuit No. 437 when wheels are turning. This pulsing action takes place about 2000 times per mile. The voltage level and pulses increase with vehicle speed. The ECM converts the pulsing voltage to MPH. The ECM uses VSS information in calculations to determine vehicle adjustments. A Code 24 will set when MPH reads less than 2 MPH and transmission is not in Park or Neutral, engine speed is greater than 1400 RPM, circuit No. 437 voltage is constant and all of these conditions have been met for 30 seconds.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) Disregard Code 24 that sets with drive wheels not turning. If speedometer is not functioning properly, service speedometer.

Test Number 2) A steady 8-12 volts at ECM connector indicates VSS circuit is open or speed sensor is faulty. A voltage of less than one volt at ECM connector indicates circuit No. 437 wire is shorted to ground. Disconnect wire at vehicle speed sensor. If voltage is now greater than 10 volts, vehicle speed sensor buffer is faulty. If voltage remains less than 8 volts, circuit is grounded. If circuit is not grounded, check for faulty ECM connector or ECM. Before replacing the ECM, PROM should be checked for correct application.