Code P0139, Oxygen sensor/Check engine light?

GENTJIM

MEMBER
2007 HYUNDAI TUCSON
2.7L
6 CYL
2WD
AUTOMATIC
100,600 MILES

Shows Code P0139, O2 Circuit Slow Response (Bank 1, Sensor 2).
I replaced the sensor as suggested and all seemed good for several days. (A couple of weeks). Then I got the check engine light again. This time I unplugged the sensor and sprayed electronic contact cleaner to flush out the plug and reconnected it. Once again, all seemed well. No codes, all monitors showed complete, and the vehicle ran very well. I now have 106,392 mileage.
This morning I got the Check Engine light again. (Non-Blinking)
Note: The catalytic converter and all sensors in both banks have been replaced now but I still keep getting this code and check engine light. I detected no vac/air leaks and cleaned the mass air sensor.
Thanks in advance. Any help is appreciated.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi,

Based on what you have done, it sounds like a connection issue. If there is excessive resistance in the wiring or connector, it could respond as mentioned. Also, the idea that it improved each time you disconnected indicates to me that is where the problem is coming from.

Do me a favor. If you have a live data scan tool, watch the affected sensor's voltages while the engine is running and at operating temperature. Let me know what they are.

On the other hand, other issues can cause the code. For example, a vacuum leak, fuel pressure issues, leaking fuel injector, exhaust leaks, and so on can all cause this to happen. But, in my mind, these things aren't temporarily fixed by disconnecting and cleaning the connector or sensor replacement. (Sorry, that's how my mind works LOL)

I attached the diagnostics below specific to the code. Some of the tests require a bidirectional scan tool and others don't. Take a look through them and let me know if you are comfortable performing them.

Take care,

Joe

See pics below.

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