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Home >> GMC >> 1989 >> Forward Control 3.9 L, Standard >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel - Standard & Electronic >> Testing >> Vehicle Speed Sensor Test >> "C" & "K" Series

"C" & "K" Series

  1. Disconnect vehicle speed sensor at transmission and check sensor resistance. If resistance is between 900-2000 ohms, reconnect harness and go to step 2). If resistance is incorrect, replace vehicle speed sensor and retest speedometer/odometer operation.
  2. Raise and support rear of vehicle. Disconnect instrument cluster connector. Start engine and place transmission in Drive. Using a digital volt/ohmmeter, check for AC voltage between Yellow wire (terminal "B13") and Purple wire (terminal "B16").
  3. If AC voltage varies with driveshaft RPM, vehicle speed sensor is okay. If no AC voltage is detected, check wires for open circuits and connectors for tightness. If wiring and connectors are okay, replace vehicle speed sensor.