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Home >> Mercury >> 2009 >> Mariner Base, 2.5 7, AWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - Symptom Charts - (Hybrid)) >> No Diagnostic Trouble Codes (DTCs) Present Symptom Charts >> Chart 7

Chart 7

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- Poor Fuel Economy

NOTE: Since driving styles can have a significant influence on fuel economy, verify the concern before starting an in-depth diagnosis.
NOTE: Excessive temperature in the high voltage traction battery will cause the engine to run longer than normal to cool the high voltage traction battery and will result in reduced fuel economy. The high voltage traction battery cooling system should be checked for proper operation if there is no obvious cause for the additional cooling request. The following external factors may also contribute to poor fuel economy conditions:
POOR FUEL ECONOMY - SYMPTOM CHART

SYSTEM/COMPONENT REFERENCE
Transaxle Fluid Level Visual. REFER to the Workshop article
Check the following PIDs:
  • LONGFT1 (value between -20 and +20)
  • VPWR (value between 10.5 and 17.0 volts, and within 0.5 volt of battery voltage)
LONGFT1 value low (-): 
Continue diagnosis. Concentrate checks in areas that cause the engine to run rich.
LONGFT1 value high (+): 
Continue diagnosis. Concentrate checks in areas that cause the engine to run lean.
VPWR not between 10.5 and 17.0 volts: 
VPWR between 10.5 and 17.0 volts, but not within 0.5 of battery voltage: 
CHECK the B+ supply to the power relay.
CHECK the VPWR circuit between the PCM and the power relay. CHECK the PWR GND circuits.
Verify the engine operates at normal temperature. Visual. REFER to ENGINE COOLING , to diagnose any cooling system concerns that are present.
Secondary Ignition System 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 .
Automatic Transaxle REFER to AUTOMATIC TRANSAXLE/TRANSMISSION EXTERNAL CONTROLS .
PCV System GO to PINPOINT TEST HG .
Additional Checks:
REFER to the applicable part in the Workshop article.
Additional Testing GO to PINPOINT TEST Z .