P1148 Subaru Closed Loop Control Function Bank 1

Possible causes

For Models 2005 and up:
– Faulty Air Fuel Ratio Sensor 1 Bank 1
– Air Fuel Ratio Sensor 1 Bank 1 circuit is open or shorted
– Air Fuel Ratio Sensor 1 Bank 1 circuit electrical connection

For Models before 2005:
– Faulty Heated Oxygen Sensor 1 Bank 1
– Heated Oxygen Sensor 1 Bank 1 circuit is open or shorted
– Heated Oxygen Sensor 1 Bank 1 circuit electrical connection

Tech description

What about the obd code?

The closed loop control function for bank 1 does not operate even when vehicle is driving in the specified condition, the closed loop control function for bank 2 does not operate even when vehicle is driving in the specified condition.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1148 Subaru Description

The Engine Control Module (ECM) performs ON/OFF duty control of the Air Fuel Ratio (A/F)/Heated Oxygen Sensor 1 heater corresponding to the engine operating condition to keep the temperature of Air Fuel Ratio (A/F)/Heated Oxygen Sensor 1 element at the specified range.