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Home >> GMC >> 1998 >> Forward Control 6.5 F >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing - 4.3L >> Engine Sensors & Switches >> Engine Controls - System & Component Testing - 4.3L >> Engine Oil Level Sensor/Switch Diagnosis

Engine Oil Level Sensor/Switch Diagnosis

  1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in TESTS W/CODES article.
  2. Using scan tool, observe engine oil level display. If scan tool does not display OK, go to next step. If scan tool displays OK, check for poor connections at sensor and PCM. If poor connection exists, repair as necessary. If poor connection does not exist, perform warning light diagnosis. See PCM CONTROLLED WARNING LIGHTS & GAUGES under MISCELLANEOUS PCM/VCM CONTROLS .
  3. Turn ignition switch to LOCK position. Disconnect PCM harness connectors. Using a test light connected to battery voltage, probe oil level switch signal (Brown wire) at PCM harness connector. If test light does not illuminate, go to next step. If test light illuminates, go to step 7).
  4. Ensure ignition switch is in LOCK position. Connect PCM harness connectors. Turn ignition switch to RUN position. Raise and support vehicle. Disconnect oil level switch harness connector. Measure voltage between oil level switch harness connector terminals. If battery voltage does not exist, go to next step. If battery voltage exists, go to step 8).
  5. Measure voltage at oil level signal circuit (Brown wire) at oil level switch harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 9).
  6. Check oil level switch signal circuit (Brown wire) for open, between PCM and oil level switch harness connectors. If open exists, repair as necessary and go to step 12). If open does not exist, check for poor connections at sensor and PCM. If poor connection exists, repair as necessary. If poor connection does not exist, perform warning light diagnosis. See PCM CONTROLLED WARNING LIGHTS & GAUGES under MISCELLANEOUS PCM/VCM CONTROLS .
  7. Check for poor connections at PCM. If poor connection exists, repair as necessary and go to step 12). If poor connection does not exist, go to step 11).
  8. Check for poor connections at oil level sensor. If poor connection exists, repair as necessary and go to step 12). If poor connection does not exist, go to step 10).
  9. Locate and repair open in oil level sensor ground circuit (Black/White wire). After repair are complete, go to step 12).
  10. Replace oil level switch and go to step 12).
  11. Replace PCM and go to next step.
  12. Start engine and allow to warm to normal operating temperature. Turn ignition switch to LOCK position. Allow engine to cool for 15 minutes. Turn ignition switch to RUN position. Using scan tool, observe oil level display. If scan tool does not display OK, go to step 3). If scan tool displays OK, system is okay at this time.
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