After replacing the 02 sensor the check engine light still turns on

KENYON1969

MEMBER
2000 HONDA CRV
4 CYL
4WD
AUTOMATIC
170,000 MILES

For at least the past three years, my check engine light has been on. My mechanic has been my mechanic since 1994. He has worked on my car since my original warranty has worn out. He has been a mechanic since his much younger days.

Although a complete diagnostic has been done, the light still stays on. When it comes to inspection, my mechanic uses the OBDII Scanner to check out the car fully and to get the light to go out. But a day or two later the light comes back on. I return to the mechanic and he was able to turn the light off. A few days later, the check engine light light came back on. The mechanic also informed me what to look for "driving wise" when the light came on. He also included the light came on as a default from Honda automobiles. The O2 Sensor was changed but the check engine light light would still come on.

Can there possibly be another problem or remedy?

6 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

I need the code number that was set so I can get you a flow chart to determine the failure. Clearing the light does absolutely nothing at all. The code needs to be identified, repairs made, and then the light should be reset.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please post the code number so I can continue to help.

Roy

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Wednesday, September 22nd, 2021 AT 6:44 AM

AL514

MECHANIC
4,793 POSTS

Hello, the check engine light comes on because of a fault in the system. It stores a Diagnostic Code, which a technician will use to start to track down the problem or the reason the light is on.

For example; if your car had a signal coming from the MAP sensor that was out of range for the RPMs and driving conditions at that moment, and the engine computer (ECM or PCM) sees this same signal a certain number of drive cycles, it will flag a code for that sensor. A code such as, MAP sensor input low, or input high, etc.

All your mechanic is doing is erasing the code each time the light comes on and the ECM is seeing the problem again in a day or so and setting the code again.
Did he say why he changed the 02 sensor and which 02 sensor did he change? Because on Hondas the front sensor is not actually an 02 sensor, it's a wide band A/F sensor and the rear sensor is a regulator 02 sensor. If you take your car to AutoZone or Advanced Auto, any parts store really, they can scan the vehicle for codes for free and they will tell you what the actual code is.
What did he tell you to look for while driving?
Here is a guide to the Check Engine light operation:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

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Wednesday, September 22nd, 2021 AT 7:02 AM

KENYON1969

MEMBER
6 POSTS

The codes I see on the Mechanic invoice is: PO131, PO171, P1457.
AutoZone Printout P0131, HO2S-(Bank 1 Sensor) Circuit Low Input

After checking my previous receipts on the working of my car, it does not look as if my O2 sensor was ever replaced. While it may have been on for the previous years, the mechanic would only turn the light off. In Inspections only, 2018 to 2021, (because it is an annual event) if the light would come on, the Mechanic would turn it off, for Inspection to pass. And tell me, what to look for, if a "real" problem came forward. The past year has been my concern because light has been on continuous for a year.

Approximately 15 years ago I replaced the original gas cap with a universal gas cap from Stanco brand. Could a problem with the cap now?

Last year, I replaced my 15 year old Die-Hard battery, because it no longer was holding a charge.

As to what to look for. I really don't know because nothing is coming up strange and unusual. I having no other driving problems except the light is on.

In my next life, I will come back as a mechanic, but right now I'm not a mechanic but I do try to stay "automotive awareness". I will read the check engine light articles. Thank you

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Thursday, September 23rd, 2021 AT 12:58 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

Okay, I attached the possibilities for the 131 code and the flow chart.

Follow the flow chart as much as you can and let me know if you have any other questions. This could be as simple as the O2 sensor or it could be fuel-related.

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Roy

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Thursday, September 23rd, 2021 AT 2:48 PM

AL514

MECHANIC
4,793 POSTS

I owed a Honda CRV for awhile, just to be sure, check that one of the exhaust bolts hasn't broken off right down behind the exhaust manifold. They are thin bolts that rust and just snap right off before the Catalytic Converter. If the exhaust is broken right there is will allow air into the exhaust, this can cause the Oxygen Sensor to read a lean condition, (p0171 or p0131). Just good to check. Also does your vehicle have a normal idle, around 700 RPMs?