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Test 4 : Fuel Gauge Inaccurate Or Inoperative (Single Tank): Notes

  1. Perform INSTRUMENT PANEL CLUSTER (IPC) DIAGNOSTIC SYSTEM CHECK before proceeding. See INSTRUMENT PANEL CLUSTER (IPC) DIAGNOSTIC SYSTEM CHECK  under SYSTEM TEST. If INSTRUMENT PANEL CLUSTER (IPC) DIAGNOSTIC SYSTEM CHECK has been performed, go to next step.
  2. Disconnect fuel lever sender harness connector. Connect Signal Generator/Instrument Panel Tester (J-33431-C) across fuel level sender connector terminals (Purple wire on 4.3L engine or Dark Blue wire on all other engines, and Orange/Black wire). Turn ignition switch to ON position. While monitoring fuel gauge, adjust tester from 40 ohms to 250 ohms, then back to 40 ohms. At 40 ohms, fuel gauge should be near empty. At 250 ohms, fuel gauge should be near full. If fuel gauge operates properly, go to step  4. If fuel gauge does not operate properly, leave tester connected, and go to next step.
  3. Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select PCM ENHANCED EVAP DATA LIST, then FUEL LEVEL %. While monitoring scan tool, adjust tester from 40 ohms to 250 ohms, then back to 40 ohms. At 40 ohms, scan tool should display 0-14%. At 250 ohms, scan tool should display 93-100%. If scan tool displays correct percentage, go to step  11. If scan tool does not display correct percentage, go to step  5.
  4. Check for deformed fuel tank which could cause fuel level sender float arm to bind. Check for an intermittent problem caused by poor connections, a break in wire insulation, or a broken wire inside insulation. See WIRING DIAGRAMS . Repair problems as necessary. After repair, go to step  13. If no problems are found, go to step  7.
  5. Check fuel level sender signal circuit (Purple wire on 4.3L engine or Dark Blue wire on all other engines) for high resistance. See WIRING DIAGRAMS . Repair Purple wire or Dark Blue wire as necessary. After repair, go to step  13. If Purple wire or Dark Blue wire is okay, go to next step.
  6. Check fuel level sender low reference circuit (Orange/Black wire) for high resistance. See WIRING DIAGRAMS . Repair Orange/Black wire as necessary. After repair, go to step  13. If Orange/Black wire is okay, go to step  9.
  7. Remove fuel level sender. See FUEL PUMP under FUEL SYSTEM (GASOLINE) in REMOVAL, OVERHAUL & INSTALLATION - TRUCKS article. Check for foreign material in fuel tank which could cause fuel level sender float arm to bind. Check for stuck fuel level sender float arm. Repair problems as necessary. After repair, go to step  13. If no problems are found, go to next step.
  8. Check resistance across fuel level sender terminals (component side) while moving fuel level sender float arm. If resistance changes smoothly, go to DIAGNOSTIC AIDS . If resistance does not change smoothly, go to step  10.
  9. Check for poor connection at Vehicle Control Module (VCM). Repair connection as necessary. After repair, go to step  13. If connection is okay, go to step  12.
  10. Replace fuel level sender. See FUEL PUMP under FUEL SYSTEM (GASOLINE) in REMOVAL, OVERHAUL & INSTALLATION - TRUCKS article. After repair, go to step  13.
  11. Replace IPC. See INSTRUMENT PANEL CLUSTER (IPC)  under REMOVAL & INSTALLATION. After repair, go to step  13.
  12. Reprogram VCM using special manufacturer's equipment. After repair, go to next step.
  13. Recheck system operation. If fuel gauge is now operating properly, system is okay. If fuel gauge is not operating properly, return to step  2.
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