P0491 fault code
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Intermediate
Joined: Nov 2019
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P0491 fault code
Hello everyone,
I had a check engine light come up recently. Instead of spending $150 to have someone read it for me, only to have it come back on, I bought a Durametric code reader for $300. I was also curious to find out what sort of life my high mileage (160k) 996 C4S had lived. Turns out...it was charmed life with exactly 1 rev in range 2 and a few hundred in rev range 1. Best part is that the most recent rev range 1/2 events happened at 30k miles. Yeah!
But I did find a few faults that led to the check engine light:
P0300 misfire detection porsche fault code 507
P0302 misfire cylinder 2 porsche fault code 510
P0303 misfire cylinder 3 porsche fault code 512
P1325 inlet camshaft 2 porsche fault code 901
P0491 secondary air system bank 1 porsche fault code 80
Cleared all the code. Did a spirited drive (aren't they all with a 911?), everything ran and sounded great, then saw the lovely check engine light again.
Checked at home, found these codes:
P0491 secondary air system bank 1 porsche fault code 80
P1325 inlet camshaft 2 porsche fault code 901
Any suggestions? Assuming the secondary air pump needs replacing, how difficult is that job?
I had a check engine light come up recently. Instead of spending $150 to have someone read it for me, only to have it come back on, I bought a Durametric code reader for $300. I was also curious to find out what sort of life my high mileage (160k) 996 C4S had lived. Turns out...it was charmed life with exactly 1 rev in range 2 and a few hundred in rev range 1. Best part is that the most recent rev range 1/2 events happened at 30k miles. Yeah!
But I did find a few faults that led to the check engine light:
P0300 misfire detection porsche fault code 507
P0302 misfire cylinder 2 porsche fault code 510
P0303 misfire cylinder 3 porsche fault code 512
P1325 inlet camshaft 2 porsche fault code 901
P0491 secondary air system bank 1 porsche fault code 80
Cleared all the code. Did a spirited drive (aren't they all with a 911?), everything ran and sounded great, then saw the lovely check engine light again.
Checked at home, found these codes:
P0491 secondary air system bank 1 porsche fault code 80
P1325 inlet camshaft 2 porsche fault code 901
Any suggestions? Assuming the secondary air pump needs replacing, how difficult is that job?
Racer
Joined: Feb 2021
Posts: 314
Likes: 77
I just got done replacing all the parts for that system all the vacuum hoses and valves are tough. I recommend when the car is dead cold open the engine bonnet and listen or pull off the hose on the secondary air pump. It should run for about 90 seconds. If it doesn’t run it’s a very simple swap out. Remove 1 nut and two bolts then remove hose and electric plug and it comes right out 5-10 minutes
Racer
Joined: Jan 2020
Posts: 254
Likes: 99
From: San Diego
I'll respond to my limited ability since I'd looked into buying a very cheap 996 that needed a secondary pump (with other things), that and it seems threads asking if you "talk to your car" rank higher these days. Good move on the durametric vs a $150 diagnostic fee. It's like getting it for half price. That is my thinking too, if I ever get a code but haven't yet, so I keep my fingers crossed.
The secondary pump resides inside the engine compartment, driver side, just left of your knee cap when you open the hood, held by three bolts (IIRC) very easy to diy replace. It does cost almost $400 so you will want to check fuses and test it with 12v to be sure it has actually failed. You should be able to test in place too, applying 12v and disconnecting the air outlet checking for strong airflow. Since all these codes hit you at once I'd suspect your real troubles are elsewhere, plus they are all bank-1 related. I doubt you have coil problems (the missfires) as they don't likely fail more than one at a time. The camshaft code seems the most troubling. Since you have the durametric I'd check your camshaft deviations to see if you have a failure of the pads or actuator on bank-1. There are ways to check this too before digging in. You didn't say it started running rough when the codes hit so I'd still hope for the best.
Even better advice would be to hit up Porschetech3 as he is most knowledgeable here, but post those deviation numbers too.
The secondary pump resides inside the engine compartment, driver side, just left of your knee cap when you open the hood, held by three bolts (IIRC) very easy to diy replace. It does cost almost $400 so you will want to check fuses and test it with 12v to be sure it has actually failed. You should be able to test in place too, applying 12v and disconnecting the air outlet checking for strong airflow. Since all these codes hit you at once I'd suspect your real troubles are elsewhere, plus they are all bank-1 related. I doubt you have coil problems (the missfires) as they don't likely fail more than one at a time. The camshaft code seems the most troubling. Since you have the durametric I'd check your camshaft deviations to see if you have a failure of the pads or actuator on bank-1. There are ways to check this too before digging in. You didn't say it started running rough when the codes hit so I'd still hope for the best.
Even better advice would be to hit up Porschetech3 as he is most knowledgeable here, but post those deviation numbers too.
Last edited by DSC800; Mar 24, 2021 at 03:13 AM.
Rennlist Member
Joined: May 2020
Posts: 1,098
Likes: 1,230
From: SF Bay Area, CA
SAI pump is easy. Be careful with the plastic hoses. They're all really old and will break if you look at them wrong.
Here's a link to a P1325 diagnosis that has links to other diagnosis. It looks like there are a number of causes from variocam solenoids to wiring to DME to camshaft. It seems the first step is to use your durametric and see if the cam angle is reacting to the solenoid activation. Good luck!
https://www.renntech.org/topic/49783...comment-288701
Here's a link to a P1325 diagnosis that has links to other diagnosis. It looks like there are a number of causes from variocam solenoids to wiring to DME to camshaft. It seems the first step is to use your durametric and see if the cam angle is reacting to the solenoid activation. Good luck!
https://www.renntech.org/topic/49783...comment-288701
Thread Starter
Intermediate
Joined: Nov 2019
Posts: 40
Likes: 7
I'll respond to my limited ability since I'd looked into buying a very cheap 996 that needed a secondary pump (with other things), that and it seems threads asking if you "talk to your car" rank higher these days. Good move on the durametric vs a $150 diagnostic fee. It's like getting it for half price. That is my thinking too, if I ever get a code but haven't yet, so I keep my fingers crossed.
The secondary pump resides inside the engine compartment, driver side, just left of your knee cap when you open the hood, held by three bolts (IIRC) very easy to diy replace. It does cost almost $400 so you will want to check fuses and test it with 12v to be sure it has actually failed. You should be able to test in place too, applying 12v and disconnecting the air outlet checking for strong airflow. Since all these codes hit you at once I'd suspect your real troubles are elsewhere, plus they are all bank-1 related. I doubt you have coil problems (the missfires) as they don't likely fail more than one at a time. The camshaft code seems the most troubling. Since you have the durametric I'd check your camshaft deviations to see if you have a failure of the pads or actuator on bank-1. There are ways to check this too before digging in. You didn't say it started running rough when the codes hit so I'd still hope for the best.
Even better advice would be to hit up Porschetech3 as he is most knowledgeable here, but post those deviation numbers too.
The secondary pump resides inside the engine compartment, driver side, just left of your knee cap when you open the hood, held by three bolts (IIRC) very easy to diy replace. It does cost almost $400 so you will want to check fuses and test it with 12v to be sure it has actually failed. You should be able to test in place too, applying 12v and disconnecting the air outlet checking for strong airflow. Since all these codes hit you at once I'd suspect your real troubles are elsewhere, plus they are all bank-1 related. I doubt you have coil problems (the missfires) as they don't likely fail more than one at a time. The camshaft code seems the most troubling. Since you have the durametric I'd check your camshaft deviations to see if you have a failure of the pads or actuator on bank-1. There are ways to check this too before digging in. You didn't say it started running rough when the codes hit so I'd still hope for the best.
Even better advice would be to hit up Porschetech3 as he is most knowledgeable here, but post those deviation numbers too.
I think the first thing to do is confirm the operation of the SAI pump in the car. Looks like a single 2 wire connector, so not much confusion about which contacts to use to run it manually with 12V. I think I'll disconnect and start the car cold to confirm that 12V is being sent to the pump for 90 seconds. Assuming yes at start, then no after ~90s, I'll pull off the single hose, which I assume is the output, apply 12V, and feel for airflow. Will report back after.
Thanks for all the responses.
BTW is bank 1 driver or passenger side?
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Thread Starter
Intermediate
Joined: Nov 2019
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This does look quite easy. Just looked under the hood. I was expected my first engine repair to be a baptism by fire of reaching blindly into the nether region.
I think the first thing to do is confirm the operation of the SAI pump in the car. Looks like a single 2 wire connector, so not much confusion about which contacts to use to run it manually with 12V. I think I'll disconnect and start the car cold to confirm that 12V is being sent to the pump for 90 seconds. Assuming yes at start, then no after ~90s, I'll pull off the single hose, which I assume is the output, apply 12V, and feel for airflow. Will report back after.
Thanks for all the responses.
BTW is bank 1 driver or passenger side?
I think the first thing to do is confirm the operation of the SAI pump in the car. Looks like a single 2 wire connector, so not much confusion about which contacts to use to run it manually with 12V. I think I'll disconnect and start the car cold to confirm that 12V is being sent to the pump for 90 seconds. Assuming yes at start, then no after ~90s, I'll pull off the single hose, which I assume is the output, apply 12V, and feel for airflow. Will report back after.
Thanks for all the responses.
BTW is bank 1 driver or passenger side?
With the hose off, I started the car (cold) and the SAI ran strong for 90 seconds. So something else is triggering the SAI code.
The hose feels pretty easy to turn, as if the other end is not well attached to the car. I reached around and couldn't reach to the end of the hose, so I can't confirm. That would be an easy fix...if I could get to the far end. Looks like removing the alternator (sorry Phase Generator) is the only way to get to it. Any suggestions? The Phase Generator was replaced by the PO about 15k miles ago.
Nordschleife Master
Joined: Jan 2018
Posts: 7,359
Likes: 4,814
From: Delaware
U r on the right track. Pull the alt and u can inspect the hose, vac lines and the change over valve. With a bi-directional scanner ot duremetric u can activate the change over valve or pump at anytime to isolate the problem.
Thread Starter
Intermediate
Joined: Nov 2019
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OK, any tips to remove the alternator? Looks like there is an idler pulley in the serpentine belt, similar to my BMWs. Crank it clockwise and release serpentine belt. Then a couple of bolts for the alternator. How do I remove the positive and negative cables from the alternator? Any tricks or will it be obvious? Should I disconnect the battery first?
Nordschleife Master
Joined: Jan 2018
Posts: 7,359
Likes: 4,814
From: Delaware
Search google for the proceedure. Its been posted up 100 times. Biggest issue is when the upper bolt is tighted during install a floating sleeve wedges into the aluminum bracket. It can make the alt real tight. U need to be carful on prying it out and not break the bracket because its very expensive. Sime have been able to tap the sleeve over a hair to free it all up.
Thread Starter
Intermediate
Joined: Nov 2019
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I can confirm the far end of the secondary air pump hose is firmly connected at both ends. It looks like there is a valve at the far end. How can I test that? If the valve won't open, then I could see how that would throw the SAI code. I have a Durameteric scanner. How do I use it to "activate the change over valve"?
Racer
Joined: Feb 2021
Posts: 314
Likes: 77
You’ll need to hook vacuum pump up to that little vacuum hose. Put a little seafoam in the big hose coming from the pump. It will make your cats smoke massively once it’s open, if the pump wants to blow off the hose at start up it’s not opening.
the vacuum of the engine is around 20”hg with no leaks so it should open and close before that a new one will open close less then 10 in hg I believe. I would just remove it and buy a new one they get sticky it’s not that expensive of a part, I replaced that the vacuum bottle and the two changeover valves as well as the hoses for under 200$ I believe making the system like new, pelican has all the parts
you may with the durametric be able to trigger the changeover valve that lets the vacuum go to that valve. One changeover valve allows vacuum to that valve to warm up cats. The other opens up to allow vacuum to trigger the flap in the rear crossover plenum between the intake manifolds. You’ll need to test it with the engine on.
If your big pump is running you have 1 of 3 issues
1. changeover valve not activating or is leaking air.
2. Vacuum bottle or hoses are leaking air (test with a vacuum gun kit you can at auto parts for 30$
3. Vacuum valve is sticking
I think mine had all the issues so was worth just replacing it all.
kinda a pain but if you remove the two crossover plenums and lower the engine on the two front bolts by unscrewing them till the max on the threads without removing you will have room to reach back and do it
the vacuum of the engine is around 20”hg with no leaks so it should open and close before that a new one will open close less then 10 in hg I believe. I would just remove it and buy a new one they get sticky it’s not that expensive of a part, I replaced that the vacuum bottle and the two changeover valves as well as the hoses for under 200$ I believe making the system like new, pelican has all the parts
you may with the durametric be able to trigger the changeover valve that lets the vacuum go to that valve. One changeover valve allows vacuum to that valve to warm up cats. The other opens up to allow vacuum to trigger the flap in the rear crossover plenum between the intake manifolds. You’ll need to test it with the engine on.
If your big pump is running you have 1 of 3 issues
1. changeover valve not activating or is leaking air.
2. Vacuum bottle or hoses are leaking air (test with a vacuum gun kit you can at auto parts for 30$
3. Vacuum valve is sticking
I think mine had all the issues so was worth just replacing it all.
kinda a pain but if you remove the two crossover plenums and lower the engine on the two front bolts by unscrewing them till the max on the threads without removing you will have room to reach back and do it
Last edited by bantamben; May 24, 2021 at 04:14 PM.
Thread Starter
Intermediate
Joined: Nov 2019
Posts: 40
Likes: 7
You’ll need to hook vacuum pump up to that little vacuum hose. Put a little seafoam in the big hose coming from the pump. It will make your cats smoke massively once it’s open, if the pump wants to blow off the hose at start up it’s not opening.
the vacuum of the engine is around 20”hg with no leaks so it should open and close before that a new one will open close less then 10 in hg I believe. I would just remove it and buy a new one they get sticky it’s not that expensive of a part, I replaced that the vacuum bottle and the two changeover valves as well as the hoses for under 200$ I believe making the system like new, pelican has all the parts
you may with the durametric be able to trigger the changeover valve that lets the vacuum go to that valve. One changeover valve allows vacuum to that valve to warm up cats. The other opens up to allow vacuum to trigger the flap in the rear crossover plenum between the intake manifolds. You’ll need to test it with the engine on.
If your big pump is running you have 1 of 3 issues
1. changeover valve not activating or is leaking air.
2. Vacuum bottle or hoses are leaking air (test with a vacuum gun kit you can at auto parts for 30$
3. Vacuum valve is sticking
I think mine had all the issues so was worth just replacing it all.
kinda a pain but if you remove the two crossover plenums and lower the engine on the two front bolts by unscrewing them till the max on the threads without removing you will have room to reach back and do it
the vacuum of the engine is around 20”hg with no leaks so it should open and close before that a new one will open close less then 10 in hg I believe. I would just remove it and buy a new one they get sticky it’s not that expensive of a part, I replaced that the vacuum bottle and the two changeover valves as well as the hoses for under 200$ I believe making the system like new, pelican has all the parts
you may with the durametric be able to trigger the changeover valve that lets the vacuum go to that valve. One changeover valve allows vacuum to that valve to warm up cats. The other opens up to allow vacuum to trigger the flap in the rear crossover plenum between the intake manifolds. You’ll need to test it with the engine on.
If your big pump is running you have 1 of 3 issues
1. changeover valve not activating or is leaking air.
2. Vacuum bottle or hoses are leaking air (test with a vacuum gun kit you can at auto parts for 30$
3. Vacuum valve is sticking
I think mine had all the issues so was worth just replacing it all.
kinda a pain but if you remove the two crossover plenums and lower the engine on the two front bolts by unscrewing them till the max on the threads without removing you will have room to reach back and do it
Change-over valve is the rectangular pneumatic-electric actuator in the picture. There's a second one that's easier to get to. Cheap and easy to replace, so why not?
Vacuum tank looks like a serious job to replace. I will put that off unless nothing else works.
Hoses I will order and replace anything that I remove
What is the "vacuum valve?" The big silver thing in the middle of the picture? That looks (and feels) like a major job to swap out.
I think I'll order the change-over valves and hose/pipe parts and replace what's easy to get to. Then I'll put everything back in and see what happens.
Not sure if it's worth it to put the battery in and try to actuate valves with the Durametric. Might be a good next step after putting everything back in and doing a road test.