P1273 code after O2 sensor change
P1273 code after O2 sensor change
I have an 04 Altima. If the cat converter on the manifold is bad will it trigger the mas airflow sensor? I have no loss in engine power and it doesn't seem to be running ruff. The check engine light came on and it was an 02 sensor first. Changed that and drove it for a day, now the light is back on and it's giving me the P1273 code which is to my understanding the mass airflow sensor sensor. Please help!
Re: P1273 code after O2 sensor change
Which O2 sensor did you change?
That code appears to be for the A/F sensor between the cat and the motor and not the one post-cat further downstream.
That code appears to be for the A/F sensor between the cat and the motor and not the one post-cat further downstream.
Re: P1273 code after O2 sensor change
I replaced the one downstream. I take it that I need to replace the other one now? And does this cause poor gas mileage?
Re: P1273 code after O2 sensor change
Yeah, the first sensor is used to calculate your air/fuel mixture.
The second one is there to make sure your cat is working. There are ways to fool that one if you ever decide to go catless.
I'm not saying that the sensor is your problem, just that it makes more sense that the first one would be the problem given the code that you posted.
The second one is there to make sure your cat is working. There are ways to fool that one if you ever decide to go catless.
I'm not saying that the sensor is your problem, just that it makes more sense that the first one would be the problem given the code that you posted.
Re: P1273 code after O2 sensor change
Ok. I'll change that one and see what happens. If the cat was bad I would be losing power and the engine would run like crap right?
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RicerX
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Re: P1273 code after O2 sensor change
Your Mass Airflow Sensor is located on the intake just before the throttle body.
There are two o2 sensors (or airflow sensors) on the exhaust manifold - the first one is commonly referred to as the "bank 1" and the second is "bank 2". Just want to be sure you guys aren't confused on that.
The code you're throwing is that the car is running too lean. My bet is on the sensor. I don't think that it's your Cat going bad at all. there are bad mechanical problems that result from the cat going bad, along with a separate set of codes that would be thrown.
Good luck and keep us posted.
There are two o2 sensors (or airflow sensors) on the exhaust manifold - the first one is commonly referred to as the "bank 1" and the second is "bank 2". Just want to be sure you guys aren't confused on that.
The code you're throwing is that the car is running too lean. My bet is on the sensor. I don't think that it's your Cat going bad at all. there are bad mechanical problems that result from the cat going bad, along with a separate set of codes that would be thrown.
Good luck and keep us posted.
Re: P1273 code after O2 sensor change
Ok. Thanks a lot. I'll keep u posted.
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RicerX
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Re: P1273 code after O2 sensor change
http://www.scribd.com/full/15736772?acc ... 5gal3annk0
Here is a link to a Technical Service Bulletin related to exactly what you're experiencing. I might try the dealer on this one.
Here is a link to a Technical Service Bulletin related to exactly what you're experiencing. I might try the dealer on this one.
Re: P1273 code after O2 sensor change
Good find on the TSB!
Some dealerships will only honor them if the car is still under warranty, but worth a shot.
Some dealerships will only honor them if the car is still under warranty, but worth a shot.
Re: P1273 code after O2 sensor change
I'd like to add one extra source of intake/exhaust leak that can trigger this dreaded Nissan P1273 code (lean reading detected downstream). After ruling out all exhaust leaks using a smoke detector on my 2005 Altima, and other related things I came across (eg. replacing both upstream and downstreams sensors mulitiple times), I finally found the source which almost certainly triggers the code in my case. I applied gentle positive pressure into the intake manifold using the smoke leak detector while the radiator cap was off.
I noted that the pressure weeps past the intake manifold into the coolant system, as the coolant now started to rise and spill over from the hole by the coolant cap.
This means some internal gasket, most likely the headgasket, does not fully seal the coolant lines within the engine. I.e., a headgasket that is starting to go in this case will allow coolant (H2O mostly) to weep into the intake manifold and get into the combustion cycle.
Spark plug which were changed also had evaporite deposit, grey gree, likely left by the coolant.
Upstream AF sensor likely reads this highly energetic dissociated steam (at hundreds of degrees Celsius) as O2. The downstream (perhaps a few hundred Celsius cooler) O2 sensor likely reads this in different way. Computer picks up the discrepancy.
Other side effects, very high fuel trim is triggered as soon as coolant temps reach near boiling temperature. This causes expansion and pressure from the steam and thermal expansion, injecting water into intake manifold at volumes eventually sufficient to trigger the fault.
As far as youtube P1237 diagnosis help videos, I've never seen this above case suggested. Only after hunting for the source for about a year did it finally become apparent to me. Hopefully this observation and test procedure helps someone with the same issues.
I noted that the pressure weeps past the intake manifold into the coolant system, as the coolant now started to rise and spill over from the hole by the coolant cap.
This means some internal gasket, most likely the headgasket, does not fully seal the coolant lines within the engine. I.e., a headgasket that is starting to go in this case will allow coolant (H2O mostly) to weep into the intake manifold and get into the combustion cycle.
Spark plug which were changed also had evaporite deposit, grey gree, likely left by the coolant.
Upstream AF sensor likely reads this highly energetic dissociated steam (at hundreds of degrees Celsius) as O2. The downstream (perhaps a few hundred Celsius cooler) O2 sensor likely reads this in different way. Computer picks up the discrepancy.
Other side effects, very high fuel trim is triggered as soon as coolant temps reach near boiling temperature. This causes expansion and pressure from the steam and thermal expansion, injecting water into intake manifold at volumes eventually sufficient to trigger the fault.
As far as youtube P1237 diagnosis help videos, I've never seen this above case suggested. Only after hunting for the source for about a year did it finally become apparent to me. Hopefully this observation and test procedure helps someone with the same issues.