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Test H: Fuel Gauge Inaccurate Or Inoperative

  1. If IPC diagnostic system check was performed, go to next step. If IPC diagnostic system check was not performed, go to INSTRUMENT PANEL CLUSTER DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing IPC diagnostic system check, go to next step.
  2. Raise and support vehicle. Disconnect left (driver's) and right (passenger's) fuel level sensor connectors. Connect jumper wires between left fuel level sensor connector terminal "C" (Dark Blue wire) and right fuel level sensor connector terminal "C" (Light Blue wire). Connect Signal Generator And Instrument Panel Tester (J 33431-C) between left fuel level sensor connector terminals "B" (Gray wire) and "C" (Dark Blue wire). Vary resistance on signal generator and instrument panel tester 40-250 ohms. See FUEL GAUGE RESISTANCE  table to aid in testing. If fuel gauge displays proper level at corresponding resistance, go to step  4 . If fuel gauge does not display proper level at corresponding resistance, go to next step.
  3. Turn ignition on and select PCM ENHANCED EVAP data list and monitor FUEL TANK LEVEL REMAINING percent. Vary resistance on signal generator and instrument panel tester 40-250 ohms. Turn ignition off momentarily between resistance settings to update scan tool display. If scan tool displays proper level at corresponding resistance, go to step  11 . If scan tool does not display proper level at corresponding resistance, go to step  5 .
  4. Check for poor connection at fuel level sensor, high resistance in signal or low reference circuit for fuel level sensor, a misaligned fuel level sensor or deformed fuel tank. When checking for a deformed or warped fuel tank, measure resistance of suspect fuel level sensor at empty, with sensor in fuel tank, and again with sensor removed from fuel tank. Measured resistance values should be same at empty. If measured resistance values are not the same, replace fuel tank. Repair as necessary. After repairs, go to step  13 . If components are okay, go to step  7 .
  5. Check for high resistance in Dark Blue wire between left fuel level sensor connector terminal "C" and PCM connector C2 terminal No. 54. See Figure . Check for high resistance in Light Blue wire between right fuel level sensor connector terminal "C" and PCM connector C2 terminal No. 73. Repair as necessary. After repairs, go to step  13 . If circuit is okay, go to next step.
  6. Check for high resistance in Gray wire between left fuel level sensor connector terminal "B", right fuel level sensor connector terminal "B", and PCM connector C1 terminal No. 23. Repair as necessary. After repairs, go to step  13 . If circuit is okay, go to step  9 .
  7. Turn ignition off. Remove left and right fuel tank sending units. See FUEL TANK SENDING UNITS  under REMOVAL & INSTALLATION. Check for stuck float arm or interference with pump body. Check for ice or other foreign particles. Repair as necessary. After repairs, go to step  13 . If fuel tank sending unit is okay, go to next step.
  8. Using DVOM, measure resistance between both fuel level sensor connector terminals "B" and "C" (component side). Move fuel level sensor float arm from empty to full position, noting any fluctuations in resistance through out float arm range. At empty position, 250 ohms (+/- 2.4 ohms) should be measured. At full position, 40 ohms (+/- one ohm) should be measured. If resistance changes smoothly, ensure fuel level is in same range as customer concern or problem may be intermittent. To diagnose intermittent, go to INTERMITTENT TROUBLE CODE DETERMINATION in BODY CONTROL MODULES - CORVETTE article. If resistance does not change smoothly, go to step  10 .
  9. Check for poor connections at PCM. Repair as necessary. After repairs, go to step  13 . If connections are okay, go to step . 12
  10. Replace faulty fuel tank sending unit. After repairs, go to step  13 .
  11. Replace IPC. See INSTRUMENT PANEL CLUSTER  under REMOVAL & INSTALLATION. After repairs, go to step  13 .
  12. Replace PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. After repairs, go to next step.
  13. Recheck system operation to verify the repair. If system operates properly, repair is complete. If system does not operate properly, go to step  2 .
FUEL GAUGE RESISTANCE

Fuel Gauge Display Resistance (ohms) (1) Fuel Level (%)
E 24 4
1/4 43 30
1/2 57 64
3/4 95 74
F 125 96
Reserve Fuel Indicator On 30 17
(1) Resistance values only reflect specified fuel level when signal circuits for both primary (left) and secondary (right) fuel level senders are jumpered together.
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