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Test W: Fuel Gauge Inaccurate Or Inoperative: Testing

  1. If instrument cluster diagnostic system check was performed, go to next step. If instrument cluster diagnostic system check was not performed, go to INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK  under DIAGNOSTIC SYSTEM CHECKS.
  2. Disconnect 7-pin connector C420. C420 is located under right rear of vehicle, near wheelwell. See Figure. Connect Signal Generator (J33431-C) and Instrument Panel Tester between connector C420 terminals "A" (Purple wire) and "D" (Black/White wire). See Figure. Turn ignition on. Vary resistance on Signal Generator from 40-250 ohms. See FUEL LEVEL SPECIFICATIONS  table to convert from resistance to fuel gauge reading. If fuel gauge does not display correct fuel level, go to next step. If fuel gauge displays correct fuel level, go to step  4.
  3. Turn ignition off. Connect scan tool to Data Link Connector (DLC). See Figure. Turn ignition on. Vary resistance on Signal Generator from 40-250 ohms. See FUEL LEVEL SPECIFICATIONS  table to convert from resistance to fuel level in percent. Turn ignition off between resistance settings to update scan tool display. Using scan tool, select PCM EVAP data list. Observe FUEL LEVEL % parameter. If FUEL LEVEL % parameter does not match conversion, go to step  5. If FUEL LEVEL % parameter matches conversion, go to step  11.
  4. Check for poor connection at fuel level sender connector, high resistance in Purple wire between fuel level sender harness connector terminal "A" and in-line connector C420 terminal "A", White/Black wire between fuel level sender harness connector terminal "D" and in-line connector C420 terminal "D", misaligned fuel level sender or a deformed fuel tank. See Figure and Figure . If connections, circuits and components are okay, go to step  7. If fault was found and repaired, go to step  13.
  5. Check for high resistance in Purple wire between in-line connector C420 terminal "A" and Powertrain Control Module (PCM) harness connector C2 terminal No. 72. See Figure and Figure . If no problem was found, go to next step. If any problems are found and corrected, go to step  13.
  6. Check for high resistance in Black/White wire between in-line connector C420 terminal "D" and PCM harness connector C2 (Clear) terminal No. 13. If no problems are found, go to step  9. If any problems are found and corrected, go to step  13.
  7. Remove fuel level sender. See FUEL LEVEL SENDER  under REMOVAL & INSTALLATION. Check for stuck fuel level sender, fuel strainer interfering with sender float arm ice or other foreign material in fuel tank. If sending unit and fuel tank are okay, go to next step. If fault was found and repaired, go to step  13.
  8. Using DVOM, measure resistance between connector C420 terminals "A" (Purple wire) and "D" (Black/White wire) while moving the float arm. Observe DVOM reading. See Figure. If resistance changes smoothly from 40-250 ohms, go to DIAGNOSTIC AIDS . If resistance does not change smoothly from 40-250 ohms, go to step  10.
  9. Check for poor connections at PCM connector. If no problems are found, go to step  12. If any problems are found and corrected, go to step  13.
  10. Replace fuel level sender. See FUEL LEVEL SENDER  under REMOVAL & INSTALLATION. After repairs, go to step  13.
  11. Replace Instrument Panel Cluster (IPC). See INSTRUMENT PANEL CLUSTER  under REMOVAL & INSTALLATION. After repairs, go to step  13.
  12. Replace PCM. See POWERTRAIN CONTROL MODULE under REMOVAL & INSTALLATION in BODY CONTROL MODULES - DEVILLE article. After repairs, go to next step.
  13. After repairs, recheck operation of fuel gauge. If gauge operates properly, repair is complete. If gauge does not operate properly, return to step  2.
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