Possible causes

– Vacuum leak affecting bank 1 only
– Fuel injector problem bank 1
– Check for cylinder misfire on bank 1
– Engine mechanical condition
– Faulty O2 sensor.

Tech notes

Though 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.

When is the code detected?

The Engine Control Module (ECM) detected bank 1 oxygen (O2) at its lean limit

Symptoms

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

MAZDA Technical Service Bulletins for P1131 code