Hello guys! My very first post...

I had the SES light on for about 2 months. The code read by an OBD2 was P2A00 which said "O2 Sensor Circuit Range/Performance Bank 1 Sensor 1".

So I ordered the part online and today went to a mechanic to have the old sensor replaced. But when I drove home for about 5 miles, the SES light just came right back on. When I checked the ECU code, it said the same thing: P2A00, which doesn't make sense since the sensor is OEM and brand new. I don't know if the mechanic reset the ECU after installing the new sensor but I went ahead and reset it with my OBD2 when I saw the SES light again.

The light hasn't come back on since then but I haven't driven the car again that much. So I guess I will have to drive it more and see.

So now several questions:

1. Does resetting the ECU a must after replacing the oxygen sensor?

2. When I checked the voltage readings of the two oxygen sensors: B1S1 and B2S1, I got different levels: one was ~2.2 V the other ~1.8 V. Does this difference indicate any issue here, like one is working the other is not?

3. Has anyone experienced the same situation? What do you think is the problem here? A blown fuse, bad wiring, etc.?

Any comments or suggestions will be highly appreciate. Thank you.

 

cracked catalytic converter

 

Hi Lucasmdemele, could you explain why a cracked cat can possibly cause the Bank 1 Sensor 1 O2 sensor to produce false readings?

Since the sensor is upstream that comes before the cat, it doesn't really make sense to me...

By the way, the voltage readings of the two downstream O2 sensors are identical, so I assume that at least the cat is working fine. Any thought on that?

Thank you.

 

but this is the code that I had I did the same thing replace o2 sensor still got the code back I put the car up in the air and noticed where the cat bolts to the support bracket there was a hairline crack in my cat replaced and the problem was solved just something to check, hopefully it helps you.

 

Thank you for the tip. I'll check that.

But first, I'm suspecting the heater circuit inside the B1S1 sensor is not properly connected, might have something to do with bad wiring. The symptom is like this:

- When the engine is idle, the voltage on B1S1 is always lower than that on B2S1. Since the brand-new sensor is working, I assume the heater in it is not powered so the sensor doesn't get hot enough.
- When I rev up the engine, or drive the car at relatively high speed, both voltage readings go up and down as expected; and for the most part, the voltage on B1S1 tends to come very close to B2S1. I assume that at high speed, both sensors reach similar temperatures from the exhaust, and so they produce similar voltage levels.

Probably I'll check the fuse box or failing that, will look at the wiring connecting the sensor all the way to the ECU.

 

Maybe try an ECU reset

 

In fact, I've tried that several times and the code keeps coming back after a few miles...

 

It sounds like you have a scan tool, if so

(1) Look at mode $06 (OBD Fusion, monitors, mode $06 / Torque "Test Results")
and compare component/MID $41, TID $81 to $45, TID $81.
^^this is your front A/F sensor monitor test results for the heater.

(2) Check your fuel trims, I suspect bank 1 is rich.

(3) At idle, check the MAF voltage or reported flow for each bank. They should be fairly close.

You may want to spend some time on page EC-500 in the FSM.

 

wonder if the new sensor got damaged during the install by the mechanic? I would also check the connectors to ensure they are snug.

 

Thank you for the suggestions! Will check these, was recently too busy with school work...

 

In fact, I believe the new sensor is working fine since its voltage at least follows the air/fuel fluctuation, meaning the sensor is keeping track of the level of oxygen in the exhaust...

Ironically when I checked the heater inside the old sensor, still it showed a certain low resistance. My guess is that the old sensor is still good, it might have never been defective... So just because the ECU throws a code that says something is wrong with the sensor doesn't mean the sensor itself is bad and needs to be replaced. But the mechanic would tell me differently...

But I'll double check to make sure. Thank you!

 

I'm having the exact same problem right now... i just had b1s1 replaced and the SES still illuminates. I've tried everything... dis connecting and re connecting the b1s1 connector... a ECU reset but still can't get rid of the SES light

The codes im getting are: p1148 & p0031

any help would be appreciated.

 

I kind of gave up on this... Been driving with the SES on without seeing any degradation in performance. Also been busy with school work. Probably will get back to it later when I have more time.

The interesting thing is that the SES light just went off by itself about a week ago and I thought perhaps something good had happened. It then stayed off for a few days and then showed up again afterward with the same code... Weird.

Just curious, why are your codes different? What is the model year of your G37? Mine is 2009.

 

Exhaust leak... when replacing the heated O2 sensor or the A/F sensor, it is always a good idea to check if there are exhaust leaks. Those will make the light stay on.

 

Initially when the check engine light came on i had the car scanned and it was throwing this code: P2A00 ( Air fuel ratio sensor circuit range/performance Bank 1 Sensor 1)

So i just automatically assumed it was the the oxygen sensor (B1S1) and i replaced it myself and the check engine light was still there... So i took the car out for a 10 minute drive and my car began to idle really rough in the lower rpm range... almost as if the car was misfiring or was about to stall out.

So i had the car re-scanned and now it was throwing 2 codes:
P1148 (Closed Loop, Bank 1)
P0031 (H02S Heater Control Circuit Low bank 1 Sensor 1)

I checked the fuse box to see if any fuses were gone bad but everything was fine. I tried dis-connecting the o2 sensor from the connection to the motor and re-connecting to see if i might not have plugged it in hard enough but that seems to be fine. I tried an ECU reset... But nothing is working

Question: As far as exhaust leaks... is the o2 sensor extremely sensitive that it will pick up on super small leaks? because i'm still running the stock exhaust system and it is rusty in some spots now... not sure i'll even be able to pick up on small leaks if there are any