P0139 O2 Sensor Circuit Slow Response Bank 1 Sensor 2

Definition: The P0139 code indicates that the oxygen sensor located in bank 1, sensor 2 is taking longer than expected to respond to changes in exhaust gas composition. This slow response can affect engine performance and emissions.

p0139: O2 Sensor Circuit Slow Response Bank 1 Sensor 2

Typical Severity: Moderate

Common Causes

p0139: O2 Sensor Circuit Slow Response Bank 1 Sensor 2

Common causes:

• Faulty oxygen sensor
• Wiring or connector issues in the oxygen sensor circuit
• Exhaust leaks near the oxygen sensor
• Engine running rich or lean
• Faulty catalytic converter

Common Misdiagnosis

OBD2 Code: P0139

Description: O2 Sensor Circuit Slow Response (Bank 1, Sensor 2)

Common Misdiagnosis: Replacing the oxygen sensor without checking for exhaust leaks or issues with the catalytic converter.

Common Diagnostic Steps

OBD2 Code: P0139

Description: O2 Sensor Circuit Slow Response Bank 1 Sensor 2

• Verify the code with an OBD-II scanner.
• Inspect the oxygen sensor wiring and connectors for damage or corrosion.
• Check for exhaust leaks near the sensor location.
• Test the oxygen sensor’s voltage output using a multimeter to ensure it is within specifications.
• Examine the fuel system for any issues that might cause a lean or rich condition, such as vacuum leaks or faulty injectors.
• Ensure proper operation of the catalytic converter, as its efficiency can affect sensor readings.
• If necessary, replace the oxygen sensor with a new one and clear the code from the vehicle’s computer system.