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HOMESERVICE MANUALSCHEVROLET2001SUBURBAN C1500REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 15 (ENGINE CONTROLS - 6.5L - TROUBLESHOOTING)POOR FUEL ECONOMY
2001 Chevrolet Suburban C1500

Poor Fuel Economy

2001 Chevrolet Suburban C1500SECTION Poor Fuel Economy
WARNING: This page is about a different car, the 2001 GMC C3500 HD and 2001 Chevrolet C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
Poor Fuel Economy

Checks Action
DEFINITION: Fuel economy, as measured by actual road tests and several tanks of fuel, is noticeably lower than expected. Also, the economy is noticeably lower than it was on this vehicle at one time, as previously shown by actual road tests.
Preliminary Checks
  • Refer to Symptoms - Engine Controls .
  • Check air cleaner filter for dirt or being plugged.
  • Visually and physically check: vacuum hoses for splits, kinks, and proper connections.
  • Perform the Diagnostic System Check - Engine Controls .
  • Check the driving habits of the owner.
  • Is the A/C ON full time (Defroster mode ON)?
  • Are the tires at the correct pressure?
  • Are excessively heavy loads being carried?
  • Is the acceleration too much, too often?
  • Suggest to the owner to fill the fuel tank and recheck the fuel economy.
  • Suggest to the driver to read the Important Facts on Fuel Economy in the Owner Manual.
Fuel System Checks
Cooling System Checks
  • Check the engine coolant level.
  • Check the engine thermostat for always being open or for the wrong heat range.
Additional Checks
  • Check the transmission shift pattern.
  • Check the torque converter Clutch (TCC) operation. Refer to Torque Converter Diagnosis in Automatic Transmission-4L80-E. When the TCC is commanded ON, a scan tool should indicate an RPM drop.
  • Check the Service Bulletins for control module software updates.
  • Check for dragging brakes.
RENDER: 1.0x

NO RELATED

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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.