Possible Causes

NOTE: Monitor description . Detects when secondary fueling adaptation offset is too small for fuel mixture control to be maintained

Exhaust system leakage
Post catalyst heated oxygen sensor incorrectly installed
Pre catalyst heated oxygen sensor circuit short circuit to ground, short circuit to power, open circuit, high resistance
Mid catalyst heated oxygen sensor circuit short circuit to ground, short circuit to power, open circuit, high resistance
Post catalyst heated oxygen sensor circuit short circuit to ground, short circuit to power, open circuit, high resistance
Pre catalyst heated oxygen sensor contamination or failure
Post catalyst heated oxygen sensor contamination or failure