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Tachometer Control Circuit Diagnosis (Hombre 4.3L)

  1. Start engine. Vary engine speed. Observe tachometer. Turn ignition off. If tachometer indicated varying engine speed, go to step  11 . If tachometer did not vary, go to next step.
  2. Disconnect Ignition coil connector. Using ohmmeter, measure resistance between ignition coil terminal "B" (White wire) and ground. Resistance should be 1.2 ohms. If resistance is less than specified, go to next step. If resistance is higher than specified, go to step  6 .
  3. Disconnect instrument cluster. Using an ohmmeter, measure resistance between instrument cluster pins No. 8 and No. 11. Resistance should be 1.2 ohms. If resistance is less than specified, go to step  5 . If resistance is greater than specified, go to next step.
  4. Locate and repair short to ground on White wire between ignition coil and instrument cluster. Reconnect ignition coil connector. Reconnect instrument cluster. Start engine and recheck tachometer operation.
  5. Replace instrument cluster. Reconnect ignition coil connector. Start engine and recheck tachometer operation.
  6. Disconnect instrument cluster. Connect a self-powered test light between instrument cluster connector terminal No. 8 and ignition coil connector terminal "B" for White wire. If test light illuminates, go to step  8 . If light does not illuminate, go to next step.
  7. Locate and repair open circuit in White wire between ignition coil and instrument cluster. Reconnect instrument cluster and ignition coil. Start engine and recheck tachometer operation.
  8. Reconnect ignition coil connector and instrument cluster. Using a voltmeter, backprobe terminal No. 8 (White wire) of instrument cluster and ground. Start engine. Observe voltage indication. Turn ignition off. If signal voltage was present, go to next step. If signal voltage was not present, go to step  10 .
  9. Replace instrument cluster. Start engine and recheck tachometer operation.
  10. Replace ignition coil. Start engine and recheck tachometer operation.
  11. Connect scan tool to DLC. Start engine. Monitor engine speed with scan tool and instrument cluster. Instrument tachometer reading should be within 100 RPM of actual engine speed. If not as specified, go to next step.
  12. Replace instrument cluster. Start engine and recheck tachometer operation.
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