DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, economy is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

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Go to Step 2

Go to the Powertrain OBD System Check

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found, correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

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Go to Step 18

Go to Step 3

Was visual/physical check performed?

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Go to Step 4

Go to Visual /Physical check.

Check owner's driving habits for the following:

Was the answer to any of the above questions YES?

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Go to Step 5

Go to Step 6

Review the items in Step 4 with customer and advise as necessary.

Is the action complete?

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System OK

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1. Visually/physically check vacuum hoses for splits, kinks, and improper connections and routing as shown on Vehicle Emission Control Information label.
2. If a problem is found, repair as necessary.

Was a repair required?

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Go to Step 18

Go to Step 7

1. Remove and check air filter element for dirt, or for being restricted.
2. Replace air filter element if necessary.

Was a repair required?

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Go to Step 18

Go to Step 8

Important:  If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

1. Remove spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 9

1. Check engine coolant level for being low. Refer to Engine Cooling.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 10

1. Check for an incorrect or faulty engine thermostat. Refer to Cooling and Radiator .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 11

1. Check engine compression for being low. Refer to Engine Mechanical .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 12

1. Check TCC operation. Refer to 4T80-E Automatic Transaxle Diagnosis.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 13

1. Check exhaust system for possible restriction:

•	Inspect exhaust system for damaged or collapsed pipes.

•	Inspect muffler for heat distress or possible internal failure.

•	Check for a possible plugged three-way catalytic converter by checking exhaust system back pressure. Refer to Restricted Exhaust System Check.

2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 14

Check for proper calibration of speedometer.

Does the speed indicated on the speedometer closely match the vehicle speed displayed on the scan tool?

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Go to Step 16

Go to Step 15

Diagnose and repair inaccurate speedometer condition as necessary. Refer to Vehicle Speed Sensor.

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Go to Step 18

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1. Check Air intake system and crankcase for air leaks.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 17

1. Review all diagnostic procedures within this table.
2. When all procedures have been completed and no malfunctions are found, review/inspect the following:

•	Visual/physical inspection.

•	Scan Tool data.

•	Freeze Frame data/Failure Records Data.

•	All connections within a suspected circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to the Powertrain (OBD) System Check

Operate the vehicle to duplicate conditions present when the original symptom was noted.

Is symptom still present?

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Go to Step 3

Repair complete.