Diagnostic Aids

Ensure all connectors are good. Very carefully check the pass-through connector at transmission. If input sensor is not working at start-up, output sensor will read zero. If code 24 is set in computer memory, "Scan" tool will read engine RPM (input sensor signal).

Fig 1: Output Speed Sensor Diagnostic Flow Chart (1991 - 2WD "C" & "K" Series)

Courtesy of GENERAL MOTORS CORP.