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First Check Engine Light

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7 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

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YOUR RESEARCHFirst Check Engine Light

Leading reported evidence

Replace cats though�

Suggestion or failed attempt

No successful repair reported for this finding.

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Suggestion · Original poster

Not excited about possibly having to replace cats though�.

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First Check Engine Light
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Leading evidence: 'Replace cats though�' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Replace cats though�' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.

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1 matching discussions · 7 captured posts examined · 0 partial discussions

Frequently discussed actions (1)

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Replace cats though�

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster

Not excited about possibly having to replace cats though�.

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First Check Engine Light
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Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.

7 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

  • Rennlist: 1 discussions

0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.

0 acknowledgements have no verified action link; they do not establish a repair result.

Generation: 20261027T035758Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

Greetings all, I�ve had my 996 C4S for over two years now. About 6 months into ownership I took off the mufflers and have had no issues. Roughly 2years/20k miles later I�ve gotten a check engine light resulting from the cats, assuming it�s maybe a faulty reading from the oxygen sensors or something related to the cats. I had a shop clear the fault and within an hour of driving it popped up again. The engine of course is fine, I�ve noticed no weird smells, smoke, or unusual vibrations with the car. Should I be worried and/or what should I do to permanently rid the code? (Aside from putting mufflers back on, which I have no intentions of doing).

POST 2Original post

It sure would help if you gave us the code it was throwing...for 20 bones you can get an obd-II bluetooth adaptor and download a free app (torque) and you can do all this yourself w/o having to go to a shop.

POST 3Original post

Yea, with an obd II reader you should be able to check the actual code and if all the sensors are reporting data, or if one has failed. If the sensors are working it may just be the end of the road for those cats, I drove a few years with a CEL before getting mine replaced, swapping the o2 sensors was the first thing I did but wasn't the issue.

POST 4 / ORIGINAL POSTEROriginal post

I�ll get the code from the shop. Not excited about possibly having to replace cats though�.

POST 5Original post

Quotes source post: 18248704

it could be something as simple as an 02 sensor. These cars are twenty+ plus years old and an 02 sensor is a maintenance item after that long.

POST 6 / ORIGINAL POSTEROriginal post

I got the error code! P0420.

POST 7Original post

its either your 02 sensor or the cat. either way not too bad on a 911 to fix https://www.kbb.com/obd-ii/p0420/#:~...0to%20diagnose .

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