4 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHP0491 Secondary Air Injection - At a loss
Reported or suspected cause
probably the sai ports in the header flange/gasket
Suggestion or failed attempt
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
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 suspect a cause
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.
Suspected cause
Since you are only getting the SAI code for bank 1 (po491) the problem is probably the SAI ports in the header flange/gasket on bank 1 are stopped up...
Leading evidence: 'probably the sai ports in the header flange/gasket' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'probably the sai ports in the header flange/gasket' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check these yourself' (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.
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 suspect a cause
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.
Suspected cause
Since you are only getting the SAI code for bank 1 (po491) the problem is probably the SAI ports in the header flange/gasket on bank 1 are stopped up...
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
Whether you have the #9 and #11 setup or the combo, you can check these yourself.
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 can access the ports by removing the Bank 1 header/gasket to revile the SAI channels and ports and unstop them with Rifle Barrel cleaning tools....
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.
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 can access the ports by removing the Bank 1 header/gasket to revile the SAI channels and ports and unstop them with Rifle Barrel cleaning tools....
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
probably the sai ports in the header flange/gasket
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that suspect a cause
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.
Suspected cause
Since you are only getting the SAI code for bank 1 (po491) the problem is probably the SAI ports in the header flange/gasket on bank 1 are stopped up...
Outcome qualification: Negation, uncertainty or missing explicit repair resolution overrides the raw extraction signal.
sai ports in the header flange/gasket
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that suspect a cause
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.
Suspected cause
Since you are only getting the SAI code for bank 1 (po491) the problem is probably the SAI ports in the header flange/gasket on bank 1 are stopped up...
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 · 1 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261027T173940Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Since I purchased my car 8 years ago, I've always struggled with the P0491 code and passing smog. Typically, I've been able to clear my codes, do the drive cycle/drive it like normal for a few weeks and the codes would clear. That hasn't worked this smog cycle, I've been attempting to get the car ready for almost a year now. The SAI pump is running at startup, I've taken it to a shop, this was his diagnosis:
For whatever reason, after he idled the car at the shop, he was able to get the SAI monitor to show as ready, I just had to get the cat ready with normal driving. This had me optimistic because I was always able to get the cat ready but the SAI would always show as not ready. Unfortunately the cat monitor was being stubborn and not getting ready and at some point in the next few days, the SAI triggered the CEL so I was back to square one. To go to the next level of diagnostics will involve taking the intake manifold off and will result in likely thousands of dollars of labor, I'm really not keen on that right now.
Currently, the car is showing the SAI and Cat readiness monitors as not ready.
Any suggestions? Anything I can do to troubleshoot and rule things out at this point?
I have found when you have an issue with a SAI system, many times it's the vacuum hoses that are not connected. They get old, shrink in length due to heat or don't fit back on the nipple and stay there. That's where I would focus, just like the report says. I wouldn't be surprised if it is no longer engaged.
What your tech did isn't enough. In the secondary air injection schematic below, he said he checked the electric change over valve (#18) and the one-way vacuum check valve (#9 and #11, although there is a superseding valve that is both #9 and #11 built into 1 valve and I don't know how he checked them since they aren't electronic)). And he claims they all work. Whether you have the #9 and #11 setup or the combo, you can check these yourself. Disconnect the hose (#14) from the SAI fan. Find yourself a length of tubing that you can airtight connect to the end of the #14. Start the car from cold and blow into the tube connected to #14. If you can't blow into it, then you need to replace #9 and #11 and that is your problem. To replace those parts, you will need to remove the alternator but not much else.
I had the same CEL code and after I was sure the SAI fan worked, I made a length of hose and blew into it. Sure enough #9 was shot. When #9 fails, it fails in the closed position.
Since you are only getting the SAI code for bank 1 (po491) the problem is probably the SAI ports in the header flange/gasket on bank 1 are stopped up...
You can access the ports by removing the Bank 1 header/gasket to revile the SAI channels and ports and unstop them with Rifle Barrel cleaning tools....
This is a source reference. Confirm exact model applicability in the original material.
