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On-board diagnostic (OBD) codes are designed to help you or your mechanic identify possible issues in your car. However, before you attempt any fixes to resolve them, you should first understand exactly what the logged codes mean.

The P0143 code is one of many trouble codes that may be logged by your vehicle’s primary computer. Read on to learn about what it involves, its potential triggers, and common symptoms.

P0143 trouble code
Code P0143 may register if the PCM detects a potential problem with the bank 1, sensor 3 post-catcon oxygen sensor or its circuit.

What Does the P0143 Code Mean?

Diagnostic trouble code (DTC) P0143 stands for “O2 Sensor Circuit Low Voltage Bank 1 Sensor 3.” It is logged when the powertrain control module (PCM) detects a potential problem with the bank 1, sensor 3 post-catalytic converter (catcon) oxygen sensor or its circuit.

Depending on the vehicle configuration, “bank 1” may refer to the side of the engine that contains cylinder 1. “Sensor 3” refers to one of the oxygen sensors located downstream of the catalytic converter.

The oxygen sensor located at the rear of the catalytic converter (bank 1, sensor 3) measures the catcon’s efficiency in controlling emissions. The PCM uses this information to determine if the converter is in working condition.

A functional post-cat sensor will exhibit voltage differences at a slower rate than the front oxygen sensors. It typically indicates a low switching frequency between the two sensors. However, if the PCM perceives the signal voltage from the post-cat oxygen sensor to be lower than factory specifications, it will set error code P0143.

Note: The definition of code P0143 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

Vehicles that are prone to code P0143 include various models of Chevrolet (especially Chevy Silverado), Ford, GMC, Jeep, and BMW.

mechanic checking vehicle chassis
Air leaks in the exhaust that result in false readings are a possible cause of code P0143.

What are the Possible Causes of the P0143 Code?

P0143 is a generic code, so it can have many triggers. Here are the most common:

  • Air leaks in the exhaust resulting in false readings
  • Failed oxygen sensor
  • Wiring issues
  • Faulty PCM

What are the Common Symptoms of the P0143 Code?

You may notice the following symptoms if you drive a car that has a logged P0143 engine code:

  • Check engine light is on
  • Poor engine performance
  • In some cases, there may be no other abnormal symptoms

How to Diagnose the P0143 Code

Although the P0143 engine code may have similar triggers and symptoms to other DTCs, there is no universal fix for this code. Vehicles are built differently depending on the manufacturer, so the code’s exact diagnostic and repair procedures may vary.

If you’re not an advanced DIYer, don’t attempt to diagnose the code on your own. It might be best to leave the diagnosis to a professional.

check engine light p0143
An illuminated check engine light can be a sign of code P0143.

How to Fix the P0143 Code

Code P0143 may be set in vehicles of varying makes and models. It may also share similar causes and symptoms with other DTCs. However, since vehicle designs differ per manufacturer, there is no single, fail-safe solution for this code.

Always refer to the factory repair information specific to your car before DIY-ing any repairs. For instance, a solution that worked for a P0143 on a Chevy Suburban might not work for a P0143 on a Toyota Sequoia.

If you aren’t confident in your automotive know-how, it may be best to bring your vehicle to an auto shop for proper diagnosis and repair.

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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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