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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 107 (Instrument Panel - C/K Series Pickups) >> Component Tests >> Vehicle Speed Sensor Testing & Diagnosis >> Functional Test

Functional Test

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1991 GMC Pickup, 1991 GMC Cab & Chassis, 1991 GMC C3500 HD, 1991 Chevrolet Pickup, and 1991 Chevrolet Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
  1. Lift and support rear of vehicle. Disconnect instrument cluster connector. Start engine, and place transmission in Drive. Using a voltmeter, measure voltage between instrument cluster connector terminals B13 (Purple/White wire) and B16 (Light Green/Black wire) while varying engine speed.
  2. If voltage varies with engine speed, vehicle speed sensor is okay. If no voltage is present, check wires for opens and connectors for tightness. If still no voltage is present, replace vehicle speed sensor.
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