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YOUR RESEARCHP0491 and PO492 - **SOLVED!**
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Replace free of charge in 30 mins
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Performed · outcome unconfirmed · Original poster
It was a cracked vacuum tubing -diagnosed and replaced free of charge in 30 mins.
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Suggestion
I did a visual check, hoping to find something obvious, but the only thing I found was the hose from airbox to throttle body was not seated properly, causing a small gap.
Leading evidence: 'Replace free of charge in 30 mins' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check hoping' (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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Suggestion
I did a visual check, hoping to find something obvious, but the only thing I found was the hose from airbox to throttle body was not seated properly, causing a small gap.
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.
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Suggestion
I found it handy to check the lines/valves/vacuum reservoir with a hand vacuum pump.
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Suggestion
In order of increasing difficulty: Check whether the pump functions first, then perform a smoke test, and if those don�t identify and solve the problem, you�ll need to dig into the electricals.
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Suggestion
So we moved over to changing all spark plugs and coils, success all around.
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Check hoping
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Suggestion
I did a visual check, hoping to find something obvious, but the only thing I found was the hose from airbox to throttle body was not seated properly, causing a small gap.
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
In order of increasing difficulty: Check whether the pump functions first, then perform a smoke test, and if those don�t identify and solve the problem, you�ll need to dig into the electricals.
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Outcome without a verified action link
I fixed this problem on my Carrera and am working on a turbo with same codes.
P0491 Secondary Air Injection System, Bank 1 - Insufficient Flow
P0492 Secondary Air Injection System, Bank 2 - Insufficient Flow
Possible cause of fault
- Electrical fault in power supply or line between relay and secondary air injection pump
- Secondary air injection pump relay mechanically faulty
- Mechanical fault in electrical secondary air valve
- Pneumatic secondary air valve faulty/sluggish
- Electrical fault in secondary air injection pump
- Mechanical fault in secondary air injection pump or secondary air injection pump blocked
- Vacuum system leaking
- Air hose to secondary air injection pump slipped off or constricted
Went back to my dealer. It was a cracked vacuum tubing -diagnosed and replaced free of charge in 30 mins.
Benefits of a good relationship with the dealer...
Hello roadsession
I have a friend with these errors and misfiring with the engine running rough. Have diagnosed with Durametric. Did you experience misfires and rough running?
PS: he does not run his car now and the fault codes emerges straight after clearing them and running the engine.
Just got off the phone with my Indy. Similar problem (started a thread about it last week). And, I had a similar problem before and he found a cracked vacuum tube.
Good luck and can't wait for a resuloution for your problem.
TC
This may help
https://rennlist.com/forums/996-foru...omponents.html
You can use a hand vacuum pump to track the vacuum leak and even verify the SAI valve's operation.
As I mentioned in above post, we had these error codes and misfire codes as well. Were not able to check the vacuum system as our knowledge of this stops at "eeeeeehh that looks OK to me, or like a spaghetti monster".
So we moved over to changing all spark plugs and coils, success all around.
The spark plugs and coils fixed the SAI related (P0491/P0492) codes as well? That is interesting as those parts should have nothing to do with these codes.
Is this the same thing? doesn't seem to be since it says malfunction
P0491
Raw code: 0491
ECU: Engine control unit
Status: Confirmed
OBDII: Secondary air injection (AIR) system, bank 1 - malfunction
============2==============
P0492
Raw code: 0492
ECU: Engine control unit
Status: Confirmed
OBDII: Secondary air injection (AIR) system, bank 2 - malfunction
If its the one that goes to the change over valve, its behind the alternator attached to the grey valve that goes to the vaccum accumulator. Its thin, black hard plastic line.
No, 14 is the pressure supply line that feeds the motor from the sai pump. #28 is the vac line. Its sold in 1 meter sections from porsche. It goes from the accumulator (#6) to the change over valve(#18) to the valve to allow the sai to enter the motor.
All of these parts must work, be in tack or be connected for air to get from the pump into the motor. Its an overly complicated system.
Basically an electrical signal trips the change over valve to open, the vacuum then opens the sai air valve to allow pressurize air to flow into the motor.
If the hose before the change over valve is broken u will see it in the fuel curves, idle performance and during a smoke test. If after the c/o valve it will only leak when the sai is called to run.
In addition to the hose the c/o valve and the sai air valve can both fail but the can be bench tested.
My turn for this.
Is there any way to troubleshoot this other than with a shop and/or smoke machine? Are some lines more likely culprits than others?
I did a visual check, hoping to find something obvious, but the only thing I found was the hose from airbox to throttle body was not seated properly, causing a small gap. I repositioned it but have not had time to drive. Could that do it?
While this statement is true, it�s unlikely to be responsible for triggering Secondary Air Injection trouble codes due to insufficient air flow.
The DME uses the oxygen sensors to check for a lean condition when the Secondary Air Injection system is functioning. If the lean condition isn�t detected, the DME thinks there isn�t enough air being injected and will trigger the Check Engine Light to illuminate.
So if you have a vacuum leak with unmetered air, the oxygen sensors will see a lean condition, making it less likely to activate these trouble codes.
I�ve experienced �false� Secondary Air Injection trouble codes plenty of times. If I start driving while the SAI system is active, the additional fuel injected (due to a cold start) enriches the air-fuel ratio enough to trigger �SAI Insufficient Flow� trouble codes.
To truly rule out this phenomenon, I�d recommend you let the car idle until the SAI system has completed its job. Of course, there are recommendations by plenty of knowledgeable people to drive the car as soon as it�s started - so that you can better prevent bore scoring.
I�ve found a happy compromise would be to let it idle only for diagnostic purposes, and make it a daily habit to drive away as soon as it�s started. If the �false� trouble codes appear only while driving, just read the code and erase it. Any cheap OBD2 scanner will work for this purpose, and you can keep it in your car indefinitely.
Now if these SAI codes appear - even when you let it idle until the SAI system has completed its process - then you�re likely to have a genuine issue with the SAI system, and will need a thorough diagnostic.
Edit: spelling
Gonna hijack to ask if this system the same on a Turbo? I fixed this problem on my Carrera and am working on a turbo with same codes. If so, the accumulator is known to fail and crack, thus causing a leak.
Yes the system operates the same but in the mezger motor parts r in different places. On the mezger the cross over valve that feeds the other bank is knows to fail too.
Still chasing this one.
Ultimately, I know I should probably get it to my Indy for a smoke test, but I would love to avoid several hours of diagnostic time.
I can clear the codes but they come back, always after driving a few miles. Seems to be more common when the temperatures drop in to the 60s. Either of those things hint toward a particular likely cause?
Do you know if your Secondary Air Pump is functional? Do you hear a high-pitched whirring on cold-startup?
In order of increasing difficulty: Check whether the pump functions first, then perform a smoke test, and if those don�t identify and solve the problem, you�ll need to dig into the electricals.
Okay, is that while sitting in the driver�s seat, or standing at the rear with the engine lid open? If it�s the latter, I think your pump producing insufficient flow.
The latter. It's hard to hear it over the engine, but I can hear it with my head close to it.
I'll start browsing threads and searching Google, but would insufficient flow be the pump itself, or something further down the line?
I'm gonna chime in here since I literally just resolved this for a Turbo 996. the concept is the same. If you're getting the error on both sensors then it's most likely further upstream.
You Tube
My guess is the pump is failing. I can hear mine while sitting in the driver�s seat.
With the engine lid open (and with the engine running) a healthy pump sounds like a handheld vacuum cleaner - loud enough to be mildly annoying after 30 seconds.
You can try to visit an auto parts store and ask to test one of their secondary air pumps (any pump from any car will do) so you can compare and contrast the sound of yours. Contact additional stores if the first one declines.
edit: I stood at the rear of my car during a cold-start today, and I could hear the pump whining away with the engine lid closed. It ought to be clearly audible.
Hi, well the video shows what I did to solve the issue but basically it was a constriction issue. Yours looks like a straight up failure of the pump. If you have a durametric then you can try activating the pump to see if it turns on. Or take it out and plug it into a 12v DC power supply
First the sai has no effect on how the car runs. It pushes air into the exhaust at start up to dilute the emmisions.
There 3 basic parts, the pump, air injection valve and the change over valve. u can search and figure out what they look like. The change over valve has a vacuum line in and out with an electrical plug. When commanded by the dme the cgange over valve opens the vacuum, which opens the valve for the air injection. The pump also gets commanded to turn in by the dme.
So u need to comfirm the 3 componants work(bench test them) them make sure the signal is getting sent. A piwis unit ir even a duremetric can command the event.
Its overly complicated and usually with both of those codes the pump is inop or the c/o valve is not operating.
