Chart 10

Poor Fuel Economy

NOTE: Since driving styles can have a significant influence on fuel economy, verify the concern before starting an indepth diagnosis. Also, the following external factors could contribute to "poor fuel economy" conditions:

Stop/go driving
Improper tire pressure/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 TEST - CNG, FLEX-FUEL & GASOLINE ) unless noted
Transmission Fluid Level	Visual
Check The Following PIDs: DPFEGR (if equipped) (hot idle value within 0.15V of KOEO value) LONGFT1 / LONGFT2 (value between -20 and +20) VPWR (value between 10.5 and 17.0 volts, and within 0.5 volts of battery voltage)	DPFEGR PID value not within 0.15V of KOEO value: For vehicles equipped with ESM EGR: GO to H: Exhaust Gas Recirculation System Module (ESM) STEP HH34. All others: GO to E: Exhaust Gas Recirculation (EGR) Systems STEP HE57. 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: Go to the appropriate GENERATORS & REGULATORS article. VPWR between 10.5 and 17.0 volts, but not within 0.5 of battery voltage: CHECK B(+) supply to PCM power relay (or CCRM). CHECK VPWR circuit between PCM and PCM power relay or CCRM. CHECK PWR GND circuits.
Verify engine operates at normal temperature	Visual (refer to STEP 2: NO DTC(S) PRESENT SYMPTOM CHART INDEX or the appropriate ENGINE COOLING article, to diagnose 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	Natural Gas Applications: GO to B: Natural Gas Fuel Delivery System STEP HB1. All Others: GO to C: Fuel Delivery System STEP HC1.
Exhaust System	GO to F: Catalyst Efficiency Monitor and Exhaust Systems STEP HF5.
Automatic Transmission	Automatic Transaxle/Transmission - Refer to the appropriate AUTOMATIC TRANSMISSION article (Diagnosis by Symptom - Poor Performance).
PCV System	GO to G: Positive Crankcase Ventilation (PCV) System STEP HG1.
Additional Checks: Correct PCM vehicle identification (VID) block information (refer to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY - FLASH EEPROM . Brake drag Base engine concerns Incorrect PCV valve Contaminated MAF sensor Intake air system	Appropriate service information article.
Additional Testing	GO to Z: Intermittent STEP Z1.