Definition: The vehicle's fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, the fuel economy is noticeably lower than the fuel economy was on this vehicle at one time, as previously shown by an actual road test.

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

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Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is present, 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

Did you perform a visual/physical check?

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Go to Step 4

Go to Symptoms for the Visual /Physical Check.

Check the owner's driving habits.

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Go to Step 5

Go to Step 6

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

Is the action complete?

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System OK

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1. Visually/physically check the vacuum hoses for the following conditions:

•

Splits

•

Kinks

•	Improper connections and routing as shown on the Vehicle Emission Control Information label.

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

Was a repair required?

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Go to Step 18

Go to Step 7

1. Remove and check the air filter element for dirt or for a possible restriction.
2. Replace the air filter element if necessary.

Was a repair required?

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Go to Step 18

Go to Step 8

1. Remove the spark plugs. Check the spark plugs for the following conditions:

•

Wet plugs

•

Cracks

•	Excessive wear

•	Improper gap

•	Burned electrodes

•	Carbon tracking on the insulator

•	Heavy deposits

•	Refer to Ignition System Check .

Notice: Determine the cause of the oil or gas fouled spark plugs in order to avoid damage to the new spark plugs.

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

Was a problem found?

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Go to Step 18

Go to Step 9

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

Was a problem found?

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Go to Step 18

Go to Step 11

1. Check for the following Engine Mechanical problems. Refer to Engine Mechanical :

•	Low compression

•	Sticking valves

•	Hydraulic valve lifter problem

•	Leaking cylinder head gaskets

•	Worn or incorrect camshaft

•	Incorrect cam timing

•	Damaged timing belt

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

Was a problem found?

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Go to Step 18

Go to Step 12

1. Check the TCC operation. Refer to Transmission Fluid Check .
2. If a problem is present, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 13

1. Check the exhaust system for a possible restriction:
2. Inspect the exhaust system for any damaged or collapsed pipes.
3. Inspect the muffler for heat distress or for a possible internal failure.
4. Check the exhaust system back pressure for a possible plugged catalytic converter. Refer to Restricted Exhaust System Check .
5. If a problem is present, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 14

Check for a proper calibration of the speedometer.

1. Turn off the ignition.
2. Disconnect the ABS controller.
3. Connect the J 33431-B (Signal Generator) to the Vehicle Speed circuit in the ABS controller harness connector (one terminal connected to the signal circuit and the other to ground).
4. With the ignition on, turn on the tester. Monitor the speedometer and the speed displayed on a scan tool.

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

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Go to Step 16

Go to Step 15

Diagnose and repair the inaccurate speedometer condition as necessary. Refer to Electrical Diagnosis Engine Electrical .

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Go to Step 18

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1. Check for any air leaks in the following areas:

•	The throttle body mounting area

•	The Mass Air Flow (MAF) sensor

•	The duct work between the MAF and the throttle body

•	The intake manifold sealing surfaces

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

Was a problem found?

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Go to Step 18

Go to Step 17

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

•	The scan tool data

•	The Freeze Frame data

•	All of the connections within a suspected circuit and/or system

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

Was a problem found?

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Go to Step 18

Go to Step 3

Operate the vehicle under the same conditions (as closely as possible) as when the original symptom occurred.

Is the original symptom still present?

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Go to Step 3

The repair is complete. If another driveability symptom exists, refer to Symptoms .