Engine Bank Identification

An OBD Scan Tool will usually identify Oxygen (O2) Sensors by the Bank Number (B1 = Bank 1; B2 = Bank 2) and Sensor Number (S1 = Sensor 1; S2 = Sensor 2, etc.). Bank 1 is not on the same side of the engine for every vehicle.

• Bank 1 will always contain Cylinder 1. To locate Cylinder 1,
• Check for cylinder labels on spark plug wires
• Look for the cylinder that is closest to the front of the engine
• Refer to your Repair Manual (Found under 'Literature')
• Bank 2 refers to the bank opposite Bank 1
• Sensor 1 refers to the sensor before the catalytic converter (Other Terms: Upstream Sensor, Pre-Cat Sensor)
• Sensor 2+ typically refers to the sensor(s) after the catalytic converter (Other Terms: Downstream Sensor, Post-Cat Sensor)

Common O2 Sensor Locations

Vehicle and part manufacturers sometimes use different terms than diagnostic 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