Chart 10

Poor Fuel Economy

NOTE: Driving styles may have a significant influence on fuel economy. Verify the concern before starting an in-depth diagnosis. The following external factors may contribute to poor fuel economy:

stop and go driving
improper tire pressure and size
vehicle loads (such as trailer towing)
extended winter warm-up conditions
high speed driving
improper axle ratio
road/weather conditions
aftermarket add-ons
short run operations
customer expectations

SYSTEM/COMPONENT	REFERENCE (PINPOINT TESTS -- GASOLINE MODELS unless noted)
Check the following PIDs: DPFEGR (if equipped) (hot idle value within 0.15 volt of key ON, engine OFF value) LONGFT1/LONGFT2 (value between -20 and +20%) VPWR (value between 10.5 and 17.0 volts, and within 0.5 volt of battery voltage)	DPFEGR PID value not within 0.15 volt of key ON, engine OFF value: For vehicles equipped with an ESM, GO to Pinpoint Test HH . For all others, GO to Pinpoint Test HE . LONGFT1/LONGFT2 value low (-): Continue diagnosis. Concentrate checks in areas that would cause the engine to run rich. LONGFT1/LONGFT2 value high (+): Continue diagnosis. Concentrate checks in areas that would cause the engine to run lean. VPWR not between 10.5 and 17.0 volts: REFER to the appropriate CHARGING SYSTEM - GENERAL INFORMATION article . VPWR between 10.5 and 17.0 volts, but not within 0.5 volt of battery voltage: CHECK the B+ voltage to the PCM power relay. CHECK the VPWR circuit between the PCM and the PCM power relay. CHECK the PWR GND circuits.
Verify the engine operates at normal temperature.	Visual. REFER to the appropriate ENGINE COOLING article todiagnose any cooling system concerns that are present.
Secondary Ignition System	For vehicles equipped with a coil pack ignition system, GO to Pinpoint Test JC . For all others, GO to Pinpoint Test JB .
Fuel System	GO to Pinpoint Test HC .
Exhaust System	GO to Pinpoint Test HF .
Variable Camshaft Timing (VCT) System	GO to Pinpoint Test HK .
Transmission Fluid Level	Visual
Automatic Transmission	REFER to the appropriate AUTOMATIC TRANSMISSION article .
PCV System	GO to Pinpoint Test HG .
Additional Checks: Correct PCM VID block information. Refer to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) . Brake drag Base engine concerns Incorrect PCV valve Contaminated MAF sensor Intake air system	REFER to the applicable service information article .
Additional Testing	GO to Pinpoint Test Z .