Diagnostic Aids

Scan tester reading should closely match speedometer reading with drive wheels turning. If vehicle is equipped with an automatic transmission, check park/neutral switch adjustment. If no problem is found while using flow chart, see INTERMITTENTS in the appropriate TESTS W/O CODES article.

Fig 1: Code 24 Schematic (4.3L Turbo) Vehicle Speed Sensor

Fig 2: Code 24 Schematic (Astro, Safari & G, P, R & V W/O 4L80-E Transmission) Vehicle Speed Sensor

Fig 3: Code 24 Flow Chart (Except 3.1L, C & K Series & Models W/O 4L80-E Transmission) Vehicle Speed Sensor

Fig 1: Code 24 Schematic (C & K Series W/O 4L80-E Trans.) Vehicle Speed Sensor

Fig 2: Code 24 Flow Chart (C & K Series W/O 4L80-E Trans.) Vehicle Speed Sensor

Check all connections, especially those at the transmission pass-thru connector. If code is intermittent, see INTERMITTENTS in the TESTS W/O CODES article. While Code 24 is set, Scan tester will display an RPM derived from input speed.

Fig 1: Code 24 Schematic (C & K Series 2WD W/4L80-E Trans.) Vehicle Speed Sensor

Fig 2: Code 24 Flow Chart (C & K Series 2WD W/4L80-E Trans.) Vehicle Speed Sensor

Fig 1: Code 24 Schematic (2WD W/4L80-E Trans. Except C & K Series) Vehicle Speed Sensor

Fig 2: Code 24 Flow Chart (2WD W/4L80-E Trans. Except C & K Series) Vehicle Speed Sensor

Fig 1: Code 24 Schematic (4WD W/4L80-E Trans.) Vehicle Speed Sensor

Fig 2: Code 24 Flow Chart (4WD W/4L80-E Trans.) Vehicle Speed Sensor

A faulty or misadjusted Park/Neutral switch may set a false Code 24. Use Scan tester and check for proper signal in Drive, while wiggling shifter. Scan tester MPH reading should closely match speedometer when vehicle is moving. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article.

Fig 1: Code 24 Schematic (3.1L) Vehicle Speed Sensor

Fig 2: Code 24 Flow Chart (3.1L) Vehicle Speed Sensor