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997.1 C2S- CEL popped on for SAI B1 and B2, I replaced the gas cap with a brand new on as the o-ring was cracking and the code still came back. I have check the "Y" that comes off of the change over valve thats on the drives side manifold. It hold vacuum great. I ordered a replacement change over to see if that is it, no other codes. What to check next?
Does any one have a clean schematic of the vacuum system of our cars, the one on the lid pretty much sucks.
First, is the secondary air pump starting when it should? You could check the fuse and relay for that if not.
Also check the hoses to make sure they get air to the injection(egr, combi) valve.
Are you getting vacuum to the change over valve(you are talking about the solenoid)--correct when the engine is running? I would check after the valve first and see what is happening with the motor running. If vacuum is building and how long it takes. I don't have a schematic for the system but it is fairly simple. With bank one and two throwing a code I would suspect solenoid control or vacuum to it.
Last edited by latonnelier; 08-05-2019 at 05:51 PM.
First, is the secondary air pump starting when it should? You could check the fuse and relay for that if not.
Also check the hoses to make sure they get air to the injection(egr, combi) valves.
Are you getting vacuum to the change over valve(you are talking about the solenoid)--correct when the engine is running? I would check after the valve first and see what is happening with the motor running. If vacuum is building and how long it takes. I don't have a schematic for the system but it is fairly simple. With bank one and two throwing a code I would suspect solenoid control or vacuum to it.
When should the pump run on this car? Right after cold start? Is it an obvious run like other cars (I can definitely hear my audi’s run)- if that’s the case I don’t hear anything on cold start. I checked the fuse- which was good. Where is the relay? I reached out to a rennlist member who’s local so we can for run through his Durametric to see.
I thought I would see a circuit malfunction code if the relay/pump was dead but who knows....
ill have my wife cold start the car with me behind it so i it so I can actually listen. Where exactly is the pump?
Yeah, you would probably get a p0410 code or something of the sort also. I always check though to make sure the whole system is OK, starring with the main items.
The air pump should come on shortly after a cold start and run for a minute or so. I can't hear mine from the cab of my coupe, but I can hear it at the back, especially with the deck lid open.
I've had the change over valve go bad on my vw and it threw the 491 code but there are a couple of other things I mentioned above that would give the same code. If the main air house came off or was damaged you would hear that when the pump was running... Had that happen in the past.
Here's something crazy, the combi valve on my 911 are the same as on my vw but cheaper by a hundred bucks... Go figure.
I'll look tomorrow for the relay location, can't remember it now. But if you hear the pump running strong tomorrow you should be able to rule that out
Last edited by latonnelier; 08-05-2019 at 05:52 PM.
Yeah, you would probably get a p0410 code or something of the sort also. I always check though to make sure the whole system is OK, starring with the main items.
The air pump should come on shortly after a cold start and run for a minute or so. I can't hear mine from the cab of my coupe, but I can hear it at the back, especially with the deck lid open.
I've had the change over valve go bad on my vw and it threw the 491 code but there are a couple of other things I mentioned above that would give the same code. If the main air house came off or was damaged you would hear that when the pump was running... Had that happen in the past.
Here's something crazy, the combi valves on my 911 are the same as on my vw but cheaper by a hundred bucks... Go figure.
I'll look tomorrow for the relay location, can't remember it now. But if you hear the pump running strong tomorrow you should be able to rule that out
Just verified- the pump kicks right on at cold start and runs what seems to be a sufficient amount of time and then shuts off- no weird noises it sounds good. How can I check the "hoses" to see if its actually pumping- they do not seem easy to get to and getting to them to check would make it very difficult to run the car (alternator removal atleast).
I guess you heard no sounds of air escaping? Its a PITA the valve is under the intake plenum in the center and the pump is on the same bracket. The only way I know of getting to them is taking the dang alternator off. Perhaps you should check the change over valve vacuum with the engine running before taking every thing apart.
I guess you heard no sounds of air escaping? Its a PITA the valve is under the intake plenum in the center and the pump is on the same bracket. The only way I know of getting to them is taking the dang alternator off. Perhaps you should check the change over valve vacuum with the engine running before taking every thing apart.
Nope. Sounded like a regular SAI sound, no air escaping. The Change over valve is on the driviers side of the manifold correct. This one?
Sorry for the slow reply...I'm travelling and was on and off airplanes yesterday.
So, thinking about and looking at some pictures from a battery cable replacement last year; I don't see a vacuum line to the valve. Just the inlet hose from the pump. Perhaps someone could back me up on this, so it just seems to be a check valve. Then I would definitely think you would have to get at everything "back there".
I went to look at the parts schematic from autoatlanta and it shows a change over valve, but for the life of me, I don't know what it is controlling.
Here's a pic of the whole setup:
Sorry for the slow reply...I'm travelling and was on and off airplanes yesterday.
So, thinking about and looking at some pictures from a battery cable replacement last year; I don't see a vacuum line to the valve. Just the inlet hose from the pump. Perhaps someone could back me up on this, so it just seems to be a check valve. Then I would definitely think you would have to get at everything "back there".
I went to look at the parts schematic from autoatlanta and it shows a change over valve, but for the life of me, I don't know what it is controlling.
Here's a pic of the whole setup:
I removed the change over valve and it was locked up! Looks like it corroded from the inside out, tested it with a 12v supply and nothing happens. Replaced it- we’ll see if the light comes back. The fault lists a vacuum leak as a potential root cause so the system has to have some type of vacuum input.
Were you able to get the new valve? I hope that works, seems like a possibility, especially since it is stuck/cracked.
BTW...I did find this over the weekend and thought it might help for anyone that is looking at low airflow issues on the SAI system. This is from a 997 technical manual describing how this system operates...no vacuum valve
Were you able to get the new valve? I hope that works, seems like a possibility, especially since it is stuck/cracked.
BTW...I did find this over the weekend and thought it might help for anyone that is looking at low airflow issues on the SAI system. This is from a 997 technical manual describing how this system operates...no vacuum valve
997.1 SAI System Operation
Wonder if a bad O2 could set it off then? Well I guess it would just be one bank then. Wonder why the code say it could be a vacuum leak then in the DME manual. I guess if the valve didn’t fix it then it can only be the check valve or the pump.
Anyways can you send me that full technical manual? Would love to study it. rtl5009@gmail.com
It came back on today! I visited Bruce in philly last weekend and ran the pump via Durametric. It sounded good at full power but when you shut it off on wind down it sounded a little “tired”.
I just ordered a pump and valve. Going to replace the A/S cable while I’m in there.
I sure hope that helps. I have heard of the vanes in the pump breaking in some cars. And its not unreasonable that the check valve could get sticky.
Good luck, and keep us updated.
It came back on today! I visited Bruce in philly last weekend and ran the pump via Durametric. It sounded good at full power but when you shut it off on wind down it sounded a little “tired”.
I just ordered a pump and valve. Going to replace the A/S cable while I’m in there.
Hi rtl5009,
just come across this thread as I have the same P0491 and P0492 error codes on my 05 997CS. Did you replace the pump and valve? Did you identify what the problem was? Could you replace the pump and valve without dropping the engine?
I’ve done some research on the SAI system and the rusted up change over valve you picture above is nothing to do with the SAI system, it’s for the resonance valve in the rear cross pipe between the 2 intake manifolds. The Porsche part diagram is very confusing in this regard. I think it’s a mistake carried over from the 996 which did have a change over valve because the check valve was vacuum operated. On the 997 the check valve is pressure operated. When the pump is on, it just pushes the valve open.
I had these codes shortly after purchasing my 08 C4s with 66k on it. I elected to do a complete motor out service and replaced the pump along with just about every other serviceable part. I also did the clutch RMS and pulled the IMS seal.
The repair can be done by lowering the motor and taking off the plenum. However the cost to do that and the clutch would have been more then not just dropping it. The part is located in the back left corner of the motor. About the worst possible place to put it.
08-04-2019, 06:56 PM
CEL for P0491 and P0492
