8 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHNeed help with CEL P0420 Code
Reported repair
Replace 4 oxygen sensors
Reported resolution
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report a fix
1
1 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.
Reported fix · Original poster
I replaced all 4 oxygen sensors and then cleared the code again. This time my mileage was back to normal, like 25mpg highway and it lasted 180 miles before coming back.
Leading evidence: 'Replace 4 oxygen sensors' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, The most frequently discussed action is 'Replace 4 oxygen sensors' (1 discussions). For that action, 1 discussions report a resolution and 0 report an unsuccessful attempt. The most frequently reported fix is 'Replace 4 oxygen sensors', supported by resolution reports in 1 discussions. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
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.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
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.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
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.
Performed · outcome unconfirmed
Although I haven�t tried it, others have successfully used �Cataclean� to help rejuvenate their catalytic converters.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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
You need to replace the catalytic converter for Bank 1.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Replace 4 oxygen sensors
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that report a fix
1
1 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.
Reported fix · Original poster
I replaced all 4 oxygen sensors and then cleared the code again. This time my mileage was back to normal, like 25mpg highway and it lasted 180 miles before coming back.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Replace 4 oxygen sensors
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that report a fix
1
1 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.
Reported fix · Original poster
I replaced all 4 oxygen sensors and then cleared the code again. This time my mileage was back to normal, like 25mpg highway and it lasted 180 miles before coming back.
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.
8 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: 20261026T212127Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hi everyone,
I have an 02 Targa with 123k miles on it. CEL came on at about 123200 miles, I cleared the code and it came back 40 miles later. My mileage was horrible, like 10-13mpg highway. I replaced all 4 oxygen sensors and then cleared the code again. This time my mileage was back to normal, like 25mpg highway and it lasted 180 miles before coming back. Spark plugs were replaced at 120k miles. I don't notice any major performance issues.
Anybody know what the next troubleshooting step should be?
I had intermittent 0420 and 0421 codes. Car had strong smell of gas at startup. Replaced both cats and all 4 O2 sensors. All is well now. Bank 1 cat had broken matrix inside.
That�s understandable.
Although I haven�t tried it, others have successfully used �Cataclean� to help rejuvenate their catalytic converters. I�m a bit wary of it, since the product must be poured into the gas tank - I�m unsure whether it�ll cause issues to your fuel injection & delivery system.
I would personally give her the old Italian tune-up a couple of times and see if that improves things. You could try that in conjunction with Cataclean, if the instructions allow for it. Research the Cataclean first, and gauge your comfort level about using it.
Tough to pinpoint the problem over the forum. It may be be as simple as running oxy sensor extensions to solve the issue. Pretty common occurance with running 200 cell cats.
Below is an example from FVD. Plenty of other manufacturers as well. Good luck with solving the codes.
https://www.fvd.net/us-en/shop?&term...nsor+extension
I am right at 60K miles. I have been running extensions on the post-cat sensors for the last three years. It helps with CEL but not much else. As stated, one of my cats' matrices was broken into bits, so it was toast, and a cat cleaner would not help. If you are in an inspection state that follows California emission requirements, your choices for replacement are limited.
This is a source reference. Confirm exact model applicability in the original material.
