Checks
| Action
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DEFINITION: Fuel economy
is noticeably lower than expected as measured by an actual road test. The
fuel economy is also noticeably lower than it was on this vehicle at one
time (as previously shown by an actual road test).
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Preliminary
Checks
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| • | Inspect the air cleaner element (filter) for dirt or being plugged. |
| • | Visually inspect the vacuum hoses for splits, kinks and proper
connections as shown on the Vehicle Emission Control Label. |
| • | Does the owner have any of the following driving habits: |
| - | The A/C ON full time (defroster mode ON). |
| - | Excessive idling or stop-and-go driving. |
| - | The tires for correct inflation pressures. |
| - | Low CNG refill pressure (verify the fill station pressure). |
| - | Carrying excessively heavy loads. |
| - | Too much or too often acceleration. |
| • | Suggest to the owner to fill the fuel tank and to recheck the
fuel economy. |
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Fuel System Checks
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| • | Inspect the fuel system for leakage. |
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Sensor Checks
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| • | Inspect the Engine Coolant Temperature (ECT) sensor with the scan
tool. |
| • | Compare the engine coolant temperature with the ambient air temperature
on a cold engine. |
| • | Inspect for high resistant in the coolant sensor circuit if the
coolant temperature reading is more than 5 degrees greater or less
than the ambient air temperature on a cold engine. Refer to DTC P0118
ECT Sensor Circuit High Voltage or DTC P1115 ECT Sensor CKT Intermittent
High Voltage in Engine Controls - 5.0, 5.7L in the C/K Truck Service
Manual. |
| • | Check the Mass Air Flow (MAF) sensor. |
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Ignition System Checks
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| • | Inspect the spark plugs. Remove the plugs and inspect them for
the following conditions: |
| • | Inspect for an open Ignition Control (IC) circuit. |
| • | Inspect the ignition wires for the following items: |
| • | Inspect the Knock Sensor (KS) system. Refer to DTC P0327
Knock Sensor Noise Channel Low Voltage in Engine Controls - 5.0, 5.7L
in the C/K Truck Service Manual. |
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