Through the Oxygen (O2) sensor, the Engine Control Module (ECM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.
P1131 Ford – Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
Possible causes
– Faulty Oxygen Sensor
– Vacuum leak affecting bank 1 only
– Fuel injector problem bank 1
– Check for cylinder misfire on bank 1
– Engine mechanical condition
P1151 Ford – Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2
Possible causes
– Faulty Oxygen Sensor
– Fuel pressure high or low
– MAF sensor dirty/defective
– Vacuum leak on engine
– Leaking fuel injector or fuel pressure regulator
– Faulty Powertrain Control Module
Through the Oxygen (O2) sensor, the Engine Control Module (ECM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.
P1131 Ford – Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
Possible causes
– Faulty Oxygen Sensor
– Vacuum leak affecting bank 1 only
– Fuel injector problem bank 1
– Check for cylinder misfire on bank 1
– Engine mechanical condition
P1151 Ford – Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2
Possible causes
– Faulty Oxygen Sensor
– Fuel pressure high or low
– MAF sensor dirty/defective
– Vacuum leak on engine
– Leaking fuel injector or fuel pressure regulator
– Faulty Powertrain Control Module
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