DTC 24

Fig. 001 - Chart - Code 24 Vehicle Speed Sensor Circuit.:

Chart 24B:

CODE 24 VEHICLE SPEED SENSOR (VSS) (REMOTE BUFFER)

Vehicle speed is sensed by a Vehicle Speed Sensor located behind the I.P. cluster. The VSS is supplied with 12 volts from ignition and ECM. The output from the VSS to the ECM is a "toggling" of the voltage. As the speedometer turns, the 12V signal from the ECM is turned "ON" and "OFF". The faster the vehicle speed, the more rapidly the signal toggles.
Code 24 says that the ECM has seen the following:
a. Vehicle Speed Signal (voltage at Term. "16") not rising and falling.
b. RPM within an upper and lower limit.
c. Engine load (TPS) above a given value.
d. Not in P/N.
e. For more than a given time.
This could keep the Transmission Clutch Converter from applying and affect idle speed control motor operation on deceleration.



1. This step checks to see if there is a VSS signal to the ECM while turning a drive wheel. Normally voltage will vary from under 3 volts to over 6 volts as wheel is turned slowly. The faster the wheel is spun the less the variation. If the voltage varies as the wheel is turned, the problem is not in the VSS circuit, but could be a faulty ECM connection, ECM or TPS setting.
2. By checking voltage at the VSS connector, it can be determined which part of the circuit is at fault. Terminal 'A' is a buffered 12V source from the ECM and Terminal 'C' is a 12V ignition source. Terminal 'B' is ground.