O2 Sensor Identification Guide

An OBD Scan Tool will usually identify Oxygen Sensors by the Bank Number (B1 = Bank 1) and Sensor Number (S1 = Sensor 1). Bank 1 will always contain Cylinder 1, which is located closest to the front of the engine.

Part manufacturers often use different terms than scan tools to identify sensor positions. Regardless of the vehicle's engine orientation, the right or left bank is determined by viewing the engine from the rear (opposite the drive belts).

Common O2 Sensor Contaminants

Oxygen (O2) Sensors commonly fail due to contamination. When checking or replacing an O2 Sensor, visually inspect the sensor body to determine if it has been contaminated by a faulty part or substance upstream, and correct the fault before replacing the sensor.

ANTIFREEZE POISONING
Common Causes: Cracked or warped cylinder head Leaking cylinder head gasket Leaking intake manifold gasket Antifreeze Poisoned O2 Sensor

SILICONE POISONING
Common Causes: Use of an improper silicone gasket sealant on the engine Silicone Poisoned O2 Sensor

CARBON BUILDUP
Common Causes: Clogged air filter Leaking or defective fuel injector Carbon Buildup O2 Sensor