P CODES (POWERTRAIN) P0100 - P0199 P0143

    Definition of Trouble Code P0143

    Trouble code P0143 refers to an issue with the oxygen sensor circuit. Specifically, it indicates low voltage in Bank 1 Sensor 3. Oxygen sensors monitor the level of oxygen in the exhaust gases, allowing the engine control module (ECM) to adjust the air-fuel mixture for optimal efficiency and emissions. This code suggests that the ECM is receiving a lower voltage signal than expected from the sensor, which can affect the vehicle's performance and emissions.

    Diagnosing Trouble Code P0143

    Diagnosing trouble code P0143 involves several steps to pinpoint the source of the issue. Before starting, gather the necessary tools and equipment, such as an OBD-II scanner, a digital multimeter, and a repair manual specific to your vehicle.

    Step 1: Verify the code

    Begin by connecting the OBD-II scanner to the vehicle's diagnostic port and scanning for any stored trouble codes. If P0143 is present, proceed to the next step.

    Step 2: Inspect the oxygen sensor wiring and connections

    Visually inspect the wiring and connections related to Bank 1 Sensor 3. Look for signs of damage, corrosion, or loose connections. If any issues are found, repair or replace the damaged components as necessary.

    Step 3: Test the oxygen sensor voltage

    Refer to your vehicle's repair manual to locate Bank 1 Sensor 3. With the engine running and at operating temperature, use a digital multimeter to measure the sensor's voltage output. The voltage should fluctuate between approximately 0.1 and 0.9 volts. If the voltage is consistently low, the sensor is likely faulty and needs replacement.

    Step 4: Check the sensor heater circuit

    Some oxygen sensors are equipped with internal heaters to reach operating temperature faster. Consult your repair manual for the specific resistance value of the heater circuit. Using a digital multimeter, measure the resistance across the heater circuit terminals. If the resistance is outside the specified range, replace the sensor.

    Repairing Trouble Code P0143

    After diagnosing the source of the issue, take the necessary steps to repair it. Common solutions for trouble code P0143 include:

    1. Replace the oxygen sensor

    If the diagnosis indicates a faulty oxygen sensor, replace Bank 1 Sensor 3. Follow your repair manual's instructions for proper replacement procedures.

    2. Repair or replace damaged wiring or connections

    If damaged wiring or connections were identified during the diagnosis, repair or replace them as needed. Ensure all connections are secure and free from corrosion.


    Trouble code P0143 - Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 3) can affect your vehicle's performance and emissions. By following the provided step-by-step guide, you can diagnose and repair the issue to restore your vehicle's efficiency. Always consult your vehicle's repair manual for specific procedures and values related to your make and model.

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