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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, measure resistance between Dark Green wire terminals of VSS or VCM harness connector and instrument cluster harness connector terminal No. 14. If resistance is more than one ohm, repair open in Dark Green wire. If resistance is less than .5 ohm, 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.
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