Diagnostic Aids

Scan tester should indicate a vehicle speed whenever drive wheels are turning at speeds greater than 3 MPH. A faulty or misadjusted Park/Neutral switch can result in a false Code 24. Use scan tester to check for properly adjusted Park/Neutral switch in "D", "P" and "N". For additional information and testing of Park/Neutral switch, see ENGINE SENSORS & SWITCHES in I - SYS/COMP TESTS article in this section. If Code 24 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.

Fig 1: Code 24 Schematic - Vehicle Speed Sensor

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 24 Flow Chart - Vehicle Speed Sensor

Courtesy of GENERAL MOTORS CORP.