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P0143 Fuel & Air Metering
O2 Sensor Circuit Low Voltage (Bank 1 Sensor 3)
P0143 means the third oxygen sensor on bank 1 reports a persistently low voltage. Common causes are a failing sensor, an exhaust leak, or wiring problems.
🚗 Usually driveable. Sensor 3 is a post-catalyst monitor and rarely affects drivability.
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🎯 Top Causes, Ranked by Likelihood
#1 Faulty oxygen sensor $50-$300
A biased sensor reports low voltage.
#2 Exhaust leak near the sensor $50-$400
Leaked air lowers the oxygen reading.
#3 Open or high resistance wiring $50-$300
A circuit fault pulls the signal low.
🩺 Common Symptoms Check engine light Failed emissions test Catalyst monitor incomplete Usually no drivability change Minor economy change 💰 Repair Cost: DIY vs Shop
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🔧 How to Diagnose P0143 1 Read sensor 3 live data
2 Inspect for exhaust leaks near the sensor
3 Check the sensor wiring for opens
4 Replace the O2 sensor if biased low
❓ Frequently Asked Questions Can I drive with P0143?
Yes, generally. This post-catalyst sensor rarely affects drivability. Fix it for emissions.
What is the most common cause of P0143?
A failed oxygen sensor or an exhaust leak are the most common causes.
How much does P0143 cost to fix?
An oxygen sensor typically runs $50-$300 including labor.
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