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CEL PO491

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

Discussion summary

YOUR RESEARCHCEL PO491

Leading reported evidence

Check hose

Suggestion or failed attempt

No successful repair reported for this finding.

0
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 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

Check the hose from the air pump in left rear of engine bay.

Original post Read captured discussion
CEL PO491
Read full discussion summary

Leading evidence: 'Check hose' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check hose' (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.

Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.

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

Compare 1 other evidence results

Replace air oil separator

Suggestion or failed attempt

No successful repair reported for this finding.

0
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 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

I had the same code and the hose just popped off after replacing my AOS.

Original post Read captured discussion
CEL PO491
Frequently discussed actions (2)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Check hose

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

Check the hose from the air pump in left rear of engine bay.

Original post Read captured discussion
CEL PO491

Replace air oil separator

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

I had the same code and the hose just popped off after replacing my AOS.

Original post Read captured discussion
CEL PO491
Coverage and how to read this overview

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: 20261027T005001Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

CEL came on yesterday, although car runs fine. Plugged in friend's OBD and it threw out code 491, "secondary air injection, bank one". Reset it and so far so good. Any suggestions on the cause?

POST 2Original post

Check the hose from the air pump in left rear of engine bay. There are also some schematics lurking around the forums. I had the same code and the hose just popped off after replacing my AOS.

POST 3 / ORIGINAL POSTEROriginal post

Thanks, but that connection seems fine. Checking everything I can see in that area, but may have to get under it.

POST 4Original post

Quotes source post: 12884386

[Image-only post; no author-written text. Original image references:] http://www.renntech.org/forums/uploads/monthly_07_2008/post-1-1216429200.png

POST 5Original post

Quotes source post: 12884587

Do you have a scanner that can diaplay O2 sensor voltage in real-time? If the hoses are fine, you need to monitor the O2 sensors to diagnose it further. It could be bad O2 sensors or secondary air ports clogged from carbon.

POST 6 / ORIGINAL POSTEROriginal post

i don't have access to scanner that reads O2 in real time. Thanks for the schematic Kromdom. I'll check everything I can. Drove about 20 miles today with no issues. This will return, I'm sure, so I know it isn't over.

POST 7Original post

The one kromdom showed above is for 996 turbo. You should use this ones instead http://www.renntech.org/forums/topic...l-p0410-p1411/ If yours a MkII, the valves #2 and #4 are combined as one (merged into #4). After voltage visual inspection, there's not a whole lot to go on without reading the O2 sensors.

This is a source reference. Confirm exact model applicability in the original material.