LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 1999 >> Forward Control 6.5 Y, Standard >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel - Analog - G Series >> System Tests >> Speedometer/Odometer Inoperative

Speedometer/Odometer Inoperative

  1. Check Vehicle Speed Sensor, Vehicle Speed Sensor Buffer and Vehicle Control Module functions. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If problem is resolved, system is operating properly, no further action is required. If problem is not resolved, go to next step.
  2. Disconnect instrument cluster harness connector. Disconnect Vehicle Control Module (VCM) harness connector (gasoline engines) or Vehicle Speed Sensor Buffer (VSSB) at Powertrain Control Module (PCM) harness connector (diesel engines). Connect self-powered test light between instrument harness connector terminal No. B14 (Dark Green wire) and ground. If test does not light, go to next step. If test light lights, repair short to ground in Dark Green wire.
  3. Connect self-powered test light between instrument cluster harness connector terminal No. B14 (Dark Green wire) and VCM or VSSB harness connector Dark Green wire. If test light lights, replace instrument cluster. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION. If test light does not light, repair open in Dark Green wire.
scientia non olet · About LEMON Manuals