P0139 – OBD-II DTC

OBD-II DTC P0139 – O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

DTC P0139 meaning

DTC P0139 refers to a diagnostic trouble code indicating a high voltage condition in the oxygen sensor circuit for Bank 1 Sensor 2. This sensor is typically located after the catalytic converter and is responsible for monitoring the efficiency of the catalytic converter by measuring the oxygen levels in the exhaust gases. A high voltage reading suggests that the sensor is detecting an excessive amount of oxygen, which can lead to incorrect air-fuel mixture adjustments by the engine control unit (ECU).

DTC P0139 symptoms

Common symptoms associated with DTC P0139 may include:

• Check Engine Light illuminated
• Poor fuel economy
• Rough engine idle
• Increased emissions
• Loss of power during acceleration

DTC P0139 causes

Several factors can lead to the occurrence of DTC P0139, including:

• Faulty oxygen sensor (Bank 1 Sensor 2)
• Wiring issues such as shorts or open circuits in the sensor circuit
• Corroded or damaged connectors
• Exhaust leaks before the sensor
• ECU malfunction or software issues

DTC P0139 seriousness

DTC P0139 is considered a moderate to serious issue. While it may not cause immediate engine failure, it can lead to:

• Increased fuel consumption
• Higher emissions, potentially failing emissions tests
• Long-term engine damage if left unaddressed

How to diagnose DTC P0139

To diagnose DTC P0139, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the P0139 code.
2. Inspect the oxygen sensor and its wiring for visible damage or corrosion.
3. Check the sensor’s voltage output using a multimeter while the engine is running.
4. Look for exhaust leaks that could affect sensor readings.
5. Test the ECU for any software updates or malfunctions.

How to fix DTC P0139 step-by-step instructions

To fix DTC P0139, follow these steps:

1. Disconnect the battery to ensure safety while working on the vehicle.
2. Inspect and repair any damaged wiring or connectors related to the oxygen sensor.
3. Replace the faulty oxygen sensor (Bank 1 Sensor 2) if necessary.
4. Check for and repair any exhaust leaks that may affect sensor performance.
5. Reconnect the battery and clear the DTC using an OBD-II scanner.
6. Test drive the vehicle to ensure the check engine light does not reappear.

How to erase DTC P0139

To erase DTC P0139, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear Codes” option on the scanner.
4. Confirm the action to clear the trouble codes.
5. Disconnect the scanner and start the engine to verify that the check engine light remains off.

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