Code 24 - VSS Circuit: Notes

The ECM applies and monitors 12 volts on circuit No. D8. The Vehicle Speed Sensor (VSS) alternately grounds and opens circuit from ECM terminal No. D8 when vehicle is in motion. This pulsing action takes place about 4096 times per mile. ECM will calculate vehicle speed based on time between pulses. With vehicle in motion, Scan tester reading should closely match speedometer reading.

1. Code 24 will set if vehicle speed equals zero MPH when engine speed is between 1600 and 1825 RPM, MAP reading below 3.0 psi (20.7 kPa), low speed condition (low MAP voltage, high manifold vacuum), vehicle not in Park or Neutral (A/T), all conditions met for 1.5 seconds and Code 33 is not set. These conditions are met during a load deceleration. Disregard Code 24 which sets when vehicle is not in motion.