P0139 - O2 SENSOR CIRCUIT SLOW RESPONSE (BANK 1, SENSOR 2)

DTC code P0139 OBD2 basically indicates that the air-fuel ratio is not being adjusted as expected by the Oxygen Sensor (O2) signal or by the Engine Control module (ECM). Even the setting of this code may be due to the fact that after the engine is used normally, the ratio is not adjusted frequently. That is, the ECM determines that the O2 sensor has a slow response.

This code refers to Oxygen Sensor (O2) number 2 which is in bank number 1, i.e. the side of the engine where cylinder 1 is.

• The Check Engine light comes on.
• Unstable acceleration.

Fault code P0139 OBD II may mean that one or more of the following problems have occurred:

• There may be leaks in the exhaust.
• Cables or connectors related to the Oxygen Sensor (O2) may be worn or corroded, or cause a short circuit.
• The Oxygen Sensor (O2) may be defective.

The steps for the respective diagnostics and repair of diagnostic code P0139 are:

• Check for leakage. If found, repair them.
• Check the sensor and see if the cables are in good condition. Also, with their respective connectors. Repair if you find inconsistencies in one of these components or replace if necessary.
• Make sure that the Oxygen Sensor (O2) is not in poor condition, contaminated or dirty. Change if necessary.
• Inspect the Mass Air Flow Sensor (MAF) and verify that it is working properly.
• Change the O2