kmk42019

I had my check engine light come on a few days ago. I got it scanned at autozone and got an error code p0420, which research on here says its either my 02 sensors or my cat converter. Now, three and a half days later the light went off, almost right after I filled it up with premium. Is this normal, or should I still assume that my car has a problem?

Simba91102

may have been the gas cap.

LuvMyTSX

^ Yup, maybe gas cap was not tightened enough. Keep an eye on the mpg and if you are seeing a drop, it could be the O2 sensors.

nigelboyne

if the light goes out its fine prob a bad batch or stale gas/petrol,mine comes on if i put to strong a mix of e85 petrol in, a quick solution test is to dissconnect the neg terminal on the battery for a second that resets it plus you dont loose any of the elec memory ie the radio stations etc.

Daveheelga

I currently have the same issue. Engine light came on with same exact code, but mine hasn't gone off yet. If I disconnect the neg terminal, and the light comes back on, it probably means I have a real issue, right?

I called my mechanic, and he said the cost to replace my cat converter would be $970 (with factory part). I really hope I can avoid replacing it.

nigelboyne

put some high octane fuel in and dissconnect the battery first

Daveheelga

Thanks for the suggestion. I will try it!

nj2pa2nc

on my 06 tsx when the gas cap was not tightened enough I would get a tighten the gas cap message. Even after tightening it I would have to have the dealer reset it.

Simba91102

??

Simba91102

I think in your case, disconnecting the battery might have done it. Without knowing the model year of the affected car, it's hard to say. I'm pretty sure that the 04 and 05 model year cars (without the MM nanny) don't have the "tighten gas cap" message capability. So..... I'd guess that any car from 06 and up that gets a check engine light, without the "tighten gas cap" message, probably really does have emission issues. And..... emission concerns are about the only thing that will trip the check engine light. Any other problem will have it's own idiot light (oil pressure, overheat, transmission, electrical, etc)(also why there are tens of thousands of older cars driving around with the check engine light on).

Daveheelga

So, I filled my car up with high test unleaded and unhooked my battery cable. The check engine light is off, but when I went to have my emissions test done, they said that I hadn't driven enough miles for my computer to register.

Any idea how long it will be before the check engine light comes back on or before my computer will register? I really hope I can avoid replacing the cat converter.

nigelboyne

light is out you dont have a problem, but you should always use the highest octane fuel you can get honda/acuras dont like crap fuel below 95/octane

nigelboyne

glad that worked out for him simple soloution,

Daveheelga

Thanks Nigel. So, you think since the light hasn't come back on yet (I've already driven 90 miles), I should be okay with my cat converter?

I will be sure to put good gas in moving forward.

nigelboyne

when they did the emission test was the car warm ie up to working temp/ or was it let lie and turned of

Daveheelga

I had the car tested after about 15 minutes of driving. When I unplugged my battery cable, I must have kept it unplugged too long since the computer couldn't register the emissions test. Here's hoping it's going to work out okay.

nigelboyne

drive a bit longer but your problem is solved id say. these cars need to be blown out every so often they dont like 2k 3k rpm gear changes all the time vtec her in first 3 gears at least once a month, fuel with octane rating higher then 95 and quality fully synthetic oil with 7.5k max intervalls and role on 250,000miles driving trouble free

Daveheelga

Vtec her? What does that mean?

SoCaliTrojan

Your engine has two camshaft profiles, one for fuel economy, and one for performance (vtec). Your engine changes cam profiles at 6000 rpm (unless you have the hondata reflash, in which case it is 4850 rpm).

He is basically saying to keep the engine in gear longer so that it reaches higher rpms, rather than changing gears at the first possible point (around 3k RPMs).

Daveheelga

Cool. I will shift to manual and try what you suggest. Thanks for the explanation.