I have some Questions about the the SES light

[pathfinder9035]

well...my pathfinder check engine light is on for an o2 sensor, just one of them are bad.

i just had new tires put on and their bigger...245 75 16's.

i know those tires can make the vehicle seam a little slower since its bigger but lately i've really been noticing lack of power to the point where its hard to even keep 80 mph in 5th gear without the pedal half way or more pushed to the floor.

before maintaining 80 mph was a breeze in 5th gear almost effortless. maybe 1/4 throttle alittle more.

well my question is does the check engine light rob u of power when it is on?

another question is at 3000 rpm when i push it, for example merging into the highway at a dead stop, i hear a rattling noise. What do u guys think it is...maybe just my heat shields? Or maybe the power valve screws getting loose or something. i am getting very paranoid about it.

i am just very curious and paranoid and , well i hope i get some answers...thanks in advance.

[exvin]

Defnitely sure the ratling is the heat shield...I was under the truck the other day when I was doing my oil change and I notice that my own heat shield is like almost off...

Unsure about the lack of power due to the SES light, mines came on once but I did not notice any difference in power...I just took it to the dealership and had them check it out

[timmack]

the light itself doesnt affect performance, it only lets you know if there is something going on that the ECU doesnt like. as far as the rattling, i would check the heat shields like exvin said, thats a pretty common issue with the R50. the bad O2 can definitely affect performance, also the MAF is a common issue with these as well, and can also affect how it runs. change the O2, clean the MAF and see what happens. you mentioned in an earlier post about getting crappy gas mileage lately, that O2 might be the culprit. mine dropped noticably before i change my O2's but afterwards it went back up, i gained about 2-3 mpgs immediately.