Skip the auto shop - Our mechanics make house calls

Q: After sensor replacement, 2nd diagnostic revealed P0139

asked by on

Two days ago I took my car to the dealership because the check engine light was on. They told me it was the oxygen sensor and they replaced it. The next day, the same warning light was back on. I went to a local auto store where they ran a check engine diagnosis. The code read: "P0139 bank 1 sensor 2 o2 electrical circuit was responding slower than required for a predetermined period of time." I will return to the dealer to get this problem addressed. My car has approx. 57,000 miles and so far no serious problems. Do you think that the problem could be the catalytic converter or perhaps the wiring that connects the sensors?

No, it is not the catalyst. The P0139 code is for the O2 sensor before the catalyst. The code is illuminated when the engine control module is testing the O2 sensor and it cuts the fuel to see if the O2 sensor detects a lean condition within 5 seconds. If it does not, then it sets the code.

This can be caused by the evaporative vent solenoid allowing fuel vapor into the engine when it was commanded closed for the O2 sensor test. If fuel vapor leaks past the valve then the engine will get excessive fuel causing the O2 to detect it as a problem. Have the EVAP vent valve checked for leaks and replace as needed. If you need help having this looked at, a certified professional from YourMechanic can inspect the code further and determine exactly what needs repair.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I need torque rating for lower control arm

You should tighten the control arm bolts to 69 ftlbs.

Q: I have replaced the catalytic converter on a 2006 Lancer. Now the car won't start. It ran fine before the swap.

Hello there, many faults will cause a no start condition on your 2006 Mitsubishi Lancer. When problems immediately after work was performed the first step is to double check the work performed. Various common problems can prevent the engine from...

Q: My rear and front lights are out on my 2001 mitsubishi montero sports there was a small fire in the steering column.

In order to locate the cause of the short the mechanic like one from YourMechanic would need to charge time and materials to locate and repair the short and fire damaged materials. You would be charged for the first hour...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.