LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 1998 >> Forward Control 6.5 Y, Automatic >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel - MOTORHOME >> System Tests >> Speedometer Always Reads Zero Or Is Inaccurate

Speedometer Always Reads Zero Or Is Inaccurate

  1. Disconnect instrument cluster harness connector. Disconnect Vehicle Speed Sensor (VSS) buffer harness connector (diesel engine) or Vehicle Control Module (VCM) harness connector (gasoline engine). Using ohmmeter, check for continuity between Dark Green wire terminals of VSS or VCM harness connector and instrument cluster harness connector terminal No. 4. If no continuity is present, repair open in Dark Green wire. If continuity is present, go to next step.
  2. Measure resistance between instrument cluster harness connector terminal No. 14 (Dark Green wire) and ground. If resistance is more than one megohm, go to next step. If resistance is less than one megohm, repair short to ground in Dark Green wire.
  3. Measure voltage between instrument cluster harness connector terminal No. 14 (Dark Green wire) and ground. If voltage is more than one volt, repair short to voltage in Dark Green wire. If voltage is less than one volt, problem is in VSS or VCM. See TESTS W/CODES article in ENGINE PERFORMANCE section.
scientia non olet · About LEMON Manuals