Fuel Control System Too Lean Or Rich - Lotus Evora Service Notes

Lotus Service Notes

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
• P0131, P0135
• P0300, P0301, P0302, P0303
• P0111, P0112, P0113
Disable Criteria P0174 & P0175:
• P0106, P0107, P0108
• P0151, P0155
• P0300, P0304, P0305, P0306
• P0111, P0112, P0113
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.
– Baro sensor faults
2009/02
– Baro sensor faults
– Oxygen sensor faults
– Misfire faults
– Intake air temperature faults
– Oxygen sensor faults
– Misfire faults
– Intake air temperature faults
Section EMR
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