DTC 24

DTC 24 Chart (PCM):

VSS Circuit (PCM):

Circuit Description:
The Vehicle Speed Sensor (VSS) circuit consists of a magnetic induction type sensor, Vehicle Speed Signal (VSS) buffer and wiring. Gear teeth pressed on the outside diameter of the output carrier assembly induce an alternating current in the sensor. On two wheel drive vehicles, this current is transmitted to the vehicle speed signal buffer where it is passed on to the PCM. The VSS buffer compensates for various axle ratios and converts the signal to a square wave for use by the speedometer, cruise control and antilock brake system. Since vehicle speed is taken from the transfer case on four wheel drive vehicles, the transmission vehicle speed sensor signal on these units goes directly to the PCM. DTC 24 will set when vehicle speed is less than 250 RPM for 3 seconds while engine speed is greater than 3000 RPM. Park/Neutral Position (PNP) not selected.
If the input speed sensor is not operational at start up, this can cause the vehicle speed sensor to display zero.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Verifies power and ground to VSS buffer module.
2. The first test checks the vehicle speed sensor signal to the PCM.
3. Test two checks the vehicle speed sensor signal to the digital ratio adapter.
4. Test three directly verifies the vehicle speed sensor signal.

Diagnostic Aids:
Check all connections especially at the transmission pass-thru connector. Refer to "DTC 15". Powertrain Controls - ECM/PCM