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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHCEL Error: P0491 - Secondary Air Injection System Bank 1
Reported or suspected cause
secondary air pump is weak or not functioning
Suggestion or failed attempt
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
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Suspected cause
I suspect your secondary air pump is weak or not functioning.
CEL Error: P0491 - Secondary Air Injection System Bank 1
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Leading evidence: 'secondary air pump is weak or not functioning' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'secondary air pump is weak or not functioning' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Repair diy' (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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CEL Error: P0491 - Secondary Air Injection System Bank 1
Replace alternator
Suggestion or failed attempt
No successful repair reported for this finding.
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Unsuccessful attempts
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Suggestion · Original poster
What are the most obvious connections to the vacuum line/switches I could have dislodged while replacing the alternator?
CEL Error: P0491 - Secondary Air Injection System Bank 1
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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.
9 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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At the weekend I replaced the alternator , and the little plastic separator between the coolant lines (which was brittle as hell and broke when it was touched).
3 days later I am getting the check engine light:
CEL Error: P0491 - Secondary Air Injection System Bank 1
I suspect I slipped a hose or something when working in the engine bay (as its too much of a coincidence to get this right after working on the car)
Any ideas where to look?
Cheers,
--H
I got this same CEL when the vacuum lines going to my Fabspeed Valvetronic mufflers got hot and cracked. I'd look for a vacuum leak, maybe a disconnected or loose hose that got bumped during your previous work.
Good luck!
Light came on again at stop light today. Engine sounds great.
What are the most obvious connections to the vacuum line/switches I could have dislodged while replacing the alternator? Any pointers?
Cheers!
P0491 Secondary Air Injection System, Bank 1 - Below Limit
Possible cause of fault
- Fuse F3 faulty
- Open circuit to secondary air injection pump
- Short circuit to ground in the lead to secondary air injection pump
- Secondary air injection pump relay mechanically faulty
- Secondary air valve sluggish
- Secondary air injection pump (air cleaner) blocked
- Air hose to secondary air injection pump slipped off or crushed
- Secondary air injection pump faulty/stuck
That plastic separator between the coolant hoses is just waiting to be touched so it can break. Mined did the same thing. Remember the slogan "plasitcs make it possible"? That is all well and good but after a decade worth of heat cycles most automotive related plastic isn't worth sh*t.
I suspect your secondary air pump is weak or not functioning. No big deal, it's an emissions control failure. My wife's boxster has been dumping that code for about 3 years now.
Take a look at this repair DIY. It shows the vacuum connections you should be investigating. The ones circled in red easily get bumped during the alternator replacement and they can pull free on the opposite end. Good luck.
S.
http://p-car.com/996/diy/sai/mainpage.html
These are so inexpensive theres really no reason not to keep a few new extras in your Porsche parts bin.
Are you verifying that the SAI is oprerating when you first start the engine?
Cmon bro, you gotta fix this.
This is a source reference. Confirm exact model applicability in the original material.
