SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSGMC1999FORWARD CONTROL 4.3 W, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ELECTRICALGAUGESINSTRUMENT PANEL - ANALOG - G SERIESSYSTEM TESTSFUEL GAUGE IS INACCURATE (GASOLINE ENGINE)
1999 GMC Forward Control 4.3 W, Standard

Fuel Gauge Is Inaccurate (Gasoline Engine)

1999 GMC Forward Control 4.3 W, StandardSECTION Fuel Gauge Is Inaccurate (Gasoline Engine)
  1. With known amount of fuel in tank, check gauge readings. If gauge reads significantly different than known amount, go to next step. If gauge is reasonably accurate, system is okay.
  2. Perform a Powertrain OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. Go to next step.
  3. Turn ignition off. Disconnect fuel pump and sender harness connector on top of fuel tank. Turn ignition to RUN position. Using Tester (J-33431-B), jumper tester leads to Purple and Black wire terminals of harness connector. Set dial to 40 ohms. Slowly rotate dial to 250 ohms. If fuel gauge reads EMPTY, then FULL, replace fuel pump and sender. If gauge does not respond, go to next step.
  4. Turn ignition off. Disconnect Vehicle Control Module (VCM) harness connector C1. Turn ignition switch to RUN position. Using Tester (J-33431-B), connect Red tester lead to VCM harness connector terminal No. 9 (Purple wire) and other lead to ground. Set dial to 40 ohms. Slowly rotate dial to 250 ohms. If fuel gauge reads EMPTY, then FULL, go to step  8. If gauge does not respond, go to next step.
  5. Turn ignition off. Disconnect instrument cluster harness connector. Connect a fused jumper wire between instrument cluster harness connector terminal No. B17 (Pink wire) and instrument cluster connector cavity No. B17. Connect second fused jumper wire between instrument cluster harness connector terminal No. B13 (Black wire) and instrument cluster connector cavity No. B13. Using Tester (J-33431-B), connect Red tester lead to instrument cluster connector cavity B2 (Purple wire) and other lead to ground. Set dial to 40 ohms. Slowly rotate dial to 250 ohms. If fuel gauge reads EMPTY, then FULL, repair open in Purple wire. If gauge does not respond, go to next step.
  6. Connect a fused jumper wire between instrument cluster harness connector terminal No. B17 (Pink wire) and battery power. Connect second fused jumper wire between instrument cluster harness connector terminal No. B13 (Black wire) and instrument cluster connector cavity No. B13. Using Tester (J-33431-B), connect Red tester lead to instrument cluster connector cavity B2 (Purple wire) and other lead to ground. Set dial to 40 ohms. Slowly rotate dial to 250 ohms. If fuel gauge reads EMPTY, then FULL, repair open in Pink wire. If gauge does not respond, go to next step.
  7. Using ohmmeter, measure resistance between instrument cluster harness connector terminal No. B13 (Black/White or Tan/White wire) and ground. If resistance is more than 5 ohms, repair open in Black/White or Tan/White wire. If resistance is less than 5 ohms, replace instrument cluster. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION.
  8. Reconnect VCM harness connector. Turn ignition switch to RUN position. Using voltmeter, measure voltage at fuel sender harness connector Black wire terminal. If voltage is not between 4.5-5.5 volts, go to next step. If voltage is 4.5-5.5 volts, go to step  10.
  9. Turn ignition off. Disconnect Vehicle Control Module (VCM) harness connector C3. Turn ignition switch to RUN position. Measure voltage at VCM harness connector cavity No. 19 (Black wire). If voltage is between 4.5-5.5 volts, repair open in Black wire. If voltage is not between 4.5-5.5 volts, problem is with VCM. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  10. Turn ignition off. Using Tester (J-33431-B), connect Red tester lead to VCM harness connector terminal No. 19 (Black wire) at VCM side of connector. Connect Black lead of tester to VCM harness connector terminal No. 13 (White wire) Turn ignition switch to RUN position. Set dial to 40 ohms. Slowly rotate dial to 250 ohms. If fuel gauge reads EMPTY, then FULL, repair open in White wire. If gauge does not respond, problem is with VCM. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.