Hi Everyone,

I have a “Service Engine Soon” light that has come on a couple of times.

This is a 2010 Nissan Maxima with about 55,000 miles.

I had the O2 Sensor Bank 1 replaced at the recommendation of the Nissan Dealer.

The “Service Engine Soon” came on again about 10 days later.

Today, the dealer recommended replacing both O2 sensors and the catalytic converter for $6300. This sounds high, IMO. Please feel free to correct me if $6300 is “normal”.

I took it to a local mechanic first on both occasions. They could not find what the cause was. They said, a communication problem between the sensor and the computer or a software issue. They did not think it was the sensor.

I do not feel comfortable with the dealer. They provided a long list of recommended work on both visits. They used words like “critical”, “leaking”, “mount torn”. My local mechanic reviewed the list of recommendations and found nothing critical or leaking or torn, etc.

I feel like I have one over-priced option from the dealer which I do not feel confident with. My second option from my local mechanic thinks it is software issue that only the dealer can address.

QUESTION:
Anybody have similar problems?
Any recommendations?

Thanks in advance for any advice or recommendations!


CODES from DEALER below:
—
CODE from Dealer 1st time:
Cause:
VERIFIED CONCERN FOUND CODE STORED P2A00 (A/F SENSOR BANK 1). MONITORED A/F
SENSORS AND O2 SENSORS IN DATA MONITOR FOUND BANK 1 O2 SENSOR IS SLOW TO ADJUST
CAUSING LEANER CONDITION
Correction:
REPLACE O2 SENSOR BANK 1 REPLACE ONE TIME USE PARTS FOR EXHAUST

—
CODE from Dealer 2nd time:
Cause:
P1148 CLOSED LOOP-B1, P0031 CAR HAS AFTER MARKET SENSOR
Correction:
REPLACE BOTH SENSORS AND CATALYTIC CONVERTER

None of those codes justify a new cat. That's a flat out handjob.

The codes in general are for the front O2, which isn't really an O2, it's a wideband A/F. The P2A00 usually means that sensor is bad, but the ECM on Maxes compares the A/F with the rear O2, so a bad rear can sometimes fool it and cause it to incorrectly blame the A/F. I don't think that's the case here, since you didn't get the same codes this time. The P1148 is derivative, that code will usually show up with any inoperative A/F. P0031 isn't actually a code for the sensor, it's for the sensor heater. That implies they either screwed up your wiring or installed a defective A/F. It should be parts warranty, but if you don't trust them, have somebody you trust replace the A/F again.

Oh, PS - The second RO says aftermarket sensor, but I gather it's the aftermarket sensor they themselves installed after the P2A00. That's dumbs#!t on their part, but whatever happens, if you go aftermarket again, go with Denso or NTK or another reputable riceburner brand. Don't use Bosch or China-cheap.

Excellent thanks for the quick reply!

My local mechanic did the work. Dealer recommended the work. I think the dealer has more in depth diagnostic equipment.

To clarify, There are 3 sensors you are discussing. Two O2 sensors, front and rear, and third sensor, the A/F sensor. It sounds like you are recommending they replace the A/F Sensor, this was not done yet. Only "O2 sensor Bank 1".

And thanks on the recommended aftermarket brands.

No, there are four, an A/F on each bank upstream from the cat and an O2 on each bank downstream. All of your codes are arising from the bank1 A/F, which is on the back bank underneath the cowl. It's the hardest of the four to change out. You either need to remove the cowl, or loosen the subframe and mounts to let the engine tilt forward. If they replaced the O2 instead of the A/F on the first visit, chances are they replaced the wrong part. So the P0031 you're getting now may just be from the old bank1 A/F self-destructing.

ah ok, got it!
Actually someone posted on here a while back with the same codes, but for a Nissan Versa, not a Maxima.

"Yeah. Before I replaced it, I would clear the codes and they'd come back pretty quickly. Once the A/F was replaced, the codes have cleared and haven't come back on. That was almost 4K miles ago."
from this conversation:
p1148-p0031-possible-bad-o2-oxygen-sensor-t513072.html

Well, there are two different issues then. The P2A00 was a performance code and usually means a bad sensor, as I mentioned earlier. P0031 is for the internal heater and can be from power, ground, bad connections, or a failure of the new sensor. You can point your guy to the EC section of the manual here in Nico if he needs diagnostic info for the heater. A lot of independent shops don't have ready access to complete OE info:
https://www.nicoclub.com/service-manual ... 0%2FEC.pdf