Chart 10

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2005 Mercury Sable, 2005 Mercury Mountaineer, 2005 Mercury Monterey, 2005 Mercury Montego, and 2005 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.

Poor Fuel Economy

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

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 TEST - GASOLINE MODELS unless noted)
Transmission Fluid Level	Visual
Check the following PIDs: DPFEGR (if equipped) (hot idle value within 0.15 volt of KOEO 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 KOEO value: For vehicles equipped with ESM EGR: GO to H: Exhaust Gas Recirculation System Module (ESM) STEP HH27. 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: REFER to CHARGING SYSTEM - GENERAL INFORMATION .
	VPWR between 10.5 and 17.0 volts, but not within 0.5 volt of battery voltage: CHECK the B+ supply to the PCM power relay. CHECK the VPWR circuit between the PCM and the PCM power relay. CHECK PWR GND circuits.
Verify the engine operates at normal temperature.	Visual. REFER to ENGINE COOLING or the Symptom Index, 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	GO to PINPOINT TEST HC .
Exhaust System	GO to F: Catalyst Efficiency Monitor and Exhaust Systems STEP HF8.
Automatic Transmission	REFER to AUTOMATIC TRANSMISSION/TRANSAXLE .
PCV System	GO to PINPOINT TEST HG .
Additional Checks: Correct PCM vehicle identification (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 .