P0166 Fault Code

O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 3)

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0166 code indicates an issue with the oxygen sensor circuit for Bank 2 Sensor 3. This typically suggests that the vehicle's engine control module (ECM) is not receiving a signal from the oxygen sensor due to a fault in the circuit.

• Oxygen sensor function: Oxygen sensors monitor the level of oxygen in the exhaust gases to help optimize fuel efficiency and emissions.
• Bank 2: Refers to the side of the engine that does not contain cylinder 1.
• Sensor 3: Indicates that this is the third sensor in the sequence for Bank 2.

What are the symptoms of the P0166 code?

• Decreased fuel efficiency due to incorrect air-fuel mixture.
• Increased emissions and potential failure of emission tests.
• Rough idling or poor engine performance at varying speeds.
• Illuminated check engine light on the dashboard.

What causes the P0166 code?

• Damaged wiring or connectors in the oxygen sensor circuit.
• A faulty oxygen sensor that is unable to send a signal.
• Poor engine grounds or electrical connections that lead to signal disruption.
• Issues with the engine control module (ECM) affecting sensor readings.

How to fix P0166?

• Inspect the wiring and connectors for any signs of damage or corrosion.
• Test the oxygen sensor using a multimeter to check for proper operation and replace if necessary.
• Ensure all engine grounds and electrical connections are secure and in good condition.
• If the issue persists, consider checking the ECM for faults or software updates.