Code p420 general code. Catalyst

[Buhbuhj]

Still got a code after installing my full race catted pipe. I put a o2 sensor spacer on the downstream sensor and it's been fine since. Didn't need the elbow, just a straight spacer.

edit: OAR shouldn't be dropping, you need tune adjusted to fix that or something.

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[hmdballa219]

Right That's what everyone's saying but it's a stock OTS stage 1 93 octane cobb tune So I don't understand why it drops...
Can u put a link where u got it. Or point me to the right direction please.

 

[Juben]

Right That's what everyone's saying but it's a stock OTS stage 1 93 octane cobb tune So I don't understand why it drops...
Can u put a link where u got it. Or point me to the right direction please.

What brand of gas are you running? Please don't say Shell. If your OAR is dropping, that's because it's picking up knock. The OTS tunes are pretty conservative, so I wouldn't think it was a tuning problem. Trying running out all the current brand of gas you've been using (down to 0 to empty) and try using a different brand.

If an e85 station is close to you, try adding one gallon of e85 and filling the rest with 93. That'll bump the octane slightly and be a good indicator that you've been running crappy gas. That is, if the OAR goes to -1.00 and stays there.

 

[hmdballa219]

Usually speedway 93...but I think it's fine because I reset it..it drops to -0.75 then rises back up to normal -1.00.within about 15 miles. No clue why it drops tho. But yes I will do that then ...run it almost empty and add a gallon of e85 and the rest of BP 93 Oct.

 

[Juben]

Usually speedway 93...but I think it's fine because I reset it..it drops to -0.75 then rises back up to normal -1.00.within about 15 miles. No clue why it drops tho. But yes I will do that then ...run it almost empty and add a gallon of e85 and the rest of BP 93 Oct.

So, let me make sure I'm understanding you correctly.

The OAR is dropping back down to -0.75 after you reset the ECU or reflash the tune? If so, that's normal for the OTS in my experience.

As long as it's not dropping to -0.75 after you drive it around or at random times, then you're fine. The OAR can be set to start at any value. Most tuners set it to start at -1.00. Cobb doesn't set it all the way to -1.00 right off the bat (from what I've seen and experienced back when I tried the OTS maps out).

Now, here's something interesting to note. Throwing in a gallon of e85 at each fill-up will make an e15 (15% ethanol vs 10% ethanol for regular pump gas) mix. e15 is 94 octane. You can do that as much as you want without ill effects and it'll give you a little extra buffer against detonation/pre-ignition. That's a great benefit to have on any car that's being tuned for additional performance.

If your Speedway has e85, I'd suggest trying it. I've tested the e85 content at a bunch of Speedway stations across Tennessee and it always tests out to be about e90. I always through in a gallon of e85 if I'm gonna run pump (93).

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