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Rennlist

P0491 and P0492 keep comin? back

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

Discussion summary

YOUR RESEARCHP0491 and P0492 keep comin? back

Leading reported evidence

Check exhaust back pressure

Performed · outcome unconfirmed

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 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 · Original poster

- Checked exhaust back pressure on both banks, under 1PSI.

Original post Read captured discussion
P0491 and P0492 keep comin? back
Read full discussion summary

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

Read captured replies

1 matching discussions · 4 captured posts examined · 0 partial discussions

Compare 3 other evidence results

Repair line

Performed · outcome unconfirmed

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 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 · Original poster

- Found vacuum line for intake manifold flap actuator was broken, repaired line.

Original post Read captured discussion
P0491 and P0492 keep comin? back

Replace mass air flow sensor

Performed · outcome unconfirmed

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 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 · Original poster

- Replaced mass air flow sensor.

Original post Read captured discussion
P0491 and P0492 keep comin? back

Replace vacuum reservoir

Performed · outcome unconfirmed

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 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 · Original poster

- Replaced vacuum reservoir.

Original post Read captured discussion
P0491 and P0492 keep comin? back
Frequently discussed actions (4)

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

Check exhaust back pressure

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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 · Original poster

- Checked exhaust back pressure on both banks, under 1PSI.

Original post Read captured discussion
P0491 and P0492 keep comin? back

Repair line

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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 · Original poster

- Found vacuum line for intake manifold flap actuator was broken, repaired line.

Original post Read captured discussion
P0491 and P0492 keep comin? back

Replace mass air flow sensor

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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 · Original poster

- Replaced mass air flow sensor.

Original post Read captured discussion
P0491 and P0492 keep comin? back

Replace vacuum reservoir

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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 · Original poster

- Replaced vacuum reservoir.

Original post Read captured discussion
P0491 and P0492 keep comin? back
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.

4 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: 20261026T205155Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

2003 996 � and can�t seem to make these go away. See bullet point notes of what my Technician has done so far. Any suggestions are much appreciated. Thanks - Found vacuum line for intake manifold flap actuator was broken, repaired line. Vacuum system now holds vacuum. - Teed a vacuum gauge in between the air injection valve and solenoid. Commanded the solenoid on with the scan tool, the injection valve is getting 15Hg of vacuum. - With a vacuum pump, applied vacuum to the air injection valve. The valve opens at 6Hg. - Removed both exhaust manifolds. Cleaned out all secondary air passages. With exhaust manifolds off, opened the air valve and turned on the air pump. A good amount of air can be felt coming out of both cylinder head passages. - Replaced vacuum reservoir. - Replaced mass air flow sensor. - Both front oxygen sensors respond quickly to rich/lean condition. - Checked exhaust back pressure on both banks, under 1PSI. - Compared air injection pump output to a known good one, air volume is the same. - Air injection pump is receiving 12V, ground had 0.06 ohm of resistance and a 200mV voltage drop when the pump is running. - Vehicle still sets P0491, P0492.

POST 2Original post

Search this forum for P0491 and P0492. This is a common problem with the SAI and vacuum hoses. It has been covered over and over.

POST 4Original post

The downstream O2 sensors would detect a problem.....I think. Maybe they are bad

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