Lotus Evora - Fuel Control System too Lean or Rich

Lotus Service Notes Section EMR
Page 31
Fuel Control System Too Lean Or Rich
P0171 System Too Lean (Bank 1)
P0172 System Too Rich (Bank 1)
P0174 System Too Lean (Bank 2)
P0175 System Too Rich (Bank 2)
Description
The oxygen sensor sends a signal to the ECU corresponding to the exhaust gas oxygen content enabling the
ECU to maintain a 14.7:1 air/fuel ratio under normal driving conditions. The ECU can make fuel corrections of
± 30% to the calculated fuel demand. This value is then learned by the ECU over time. If the ECU determines
a rich condition exists (oxygen sensor above 450mV), it will decrease the calculated fuel demand to maintain
a 14.7:1 ratio. If the ECU determines a lean condition exists (oxygen sensor below 450mV), it will increase the
calculated fuel demand to maintain a 14.7:1 ratio.
Monitor:
• Continuous
Enable Criteria:
• FuelTrimconditionenabled
• Closedloopfuellingenabled
• MAF<28g/sec
• Altitude<8000ft(2438m),Baro>756mbar
Disable Criteria P0171 & P0172:
• P0106,P0107,P0108        –Barosensorfaults
• P0131,P0135           –Oxygensensorfaults
• P0300,P0301,P0302,P0303      –Misfirefaults
• P0111,P0112,P0113         –Intakeairtemperaturefaults
Disable Criteria P0174 & P0175:
• P0106,P0107,P0108        –Barosensorfaults
• P0151,P0155           –Oxygensensorfaults
• P0300,P0304,P0305,P0306      –Misfirefaults
• P0111,P0112,P0113         –Intakeairtemperaturefaults
Malfunction Criteria P0171 & P0174:
• Thesecodeswillsetwhentherelevantenginebanklearnedfuelcorrectionhasbeenincreasedtoitsmaximum
limit of 25% and the system still cannot maintain an air/fuel ratio of 14.7:1 under normal driving conditions.
• Thesecodeswillalsobesetiftherelevantbankfuellearninjectordeadtimeisgreaterthan450micro
seconds.
Potential failure modes:
• FuelPressuretoolow(restrictioninfuelline)
• Airleakininductionsystem
• Waterinfuel
• Exhaustleak/crackbeforefrontoxygensensor
• Injectorfault
• Sensorconnectorandwiringforsignsofcorrosionorlooseconnections
• MAFfault
• Vehiclehaspreviouslyrunoutoffuel
Diagnostic Mask:
• TheMILwillbeilluminatediffaultispresentfortwoconsecutivetrips.
2009/02