Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that one of the car's sensors, which checks how clean the exhaust is, isn't working properly. It's like a nose that can't smell anything.
The engine control module (ECM) is not detecting any activity from the oxygen sensor located on Bank 2 Sensor 3, which is responsible for monitoring the oxygen levels in the exhaust gases.
The P0166 code is triggered when the ECM detects that the oxygen sensor on Bank 2 Sensor 3 is not providing any voltage signal. This sensor is crucial for determining the air-fuel mixture by measuring the amount of oxygen in the exhaust. No activity means the sensor might be faulty or there could be an issue with the wiring or connections.
• Check Engine Light is on
• Poor fuel economy
• Failed emissions test
• Faulty oxygen sensor
• Damaged wiring or connectors
• Exhaust leaks
ECM: Engine Control Module, the computer that controls engine functions.
Oxygen Sensor: A device that measures the amount of oxygen in the exhaust gases.
• Use an OBD-II scanner to confirm the code.
• Inspect the oxygen sensor and its wiring for damage.
• Check for exhaust leaks near the sensor.
• Replace the faulty oxygen sensor.
• Repair or replace damaged wiring or connectors.
• Fix any exhaust leaks.
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $300
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regular maintenance checks
• Timely replacement of oxygen sensors
• Ensure proper exhaust system maintenance
Sensor Issue
• Address the issue promptly to avoid further damage.
• Consider professional diagnosis if unsure.
Oxygen sensors may be covered under the vehicle's emissions warranty.
Oxygen sensor codes like P0166 have been common as vehicles age and sensors wear out.
Moderate – While the vehicle may still run, ignoring this issue could lead to poor performance and increased emissions.
Driving with a faulty oxygen sensor can lead to increased emissions, which may violate local emissions laws.
• Engine at operating temperature
• Vehicle running at idle
The oxygen sensor for Bank 2 Sensor 3 is typically located downstream on the exhaust system on the side of the engine with the second set of cylinders.
Q: Can I drive with a P0166 code?
A: You can drive, but it's not recommended as it can lead to poor performance and higher emissions.
Q: How do I know if my oxygen sensor is bad?
A: Common signs include a check engine light, poor fuel economy, and failed emissions tests.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Relevant when the code or supporting diagnostics point toward upstream or downstream oxygen-sensor faults.
This code family often involves upstream or downstream oxygen-sensor diagnosis.
Verify exact sensor position and vehicle fitment before buying.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.