ZX9RCAM

My CEL had been on for about 3-4 weeks, & went off like twice for a period of
2-3 days during that time.
It has now been off, like I say for about 10 days straight (no, it is not burned out, lol).
I have the K&N cold air kit & I seem to remember the codes I was pulling
had to do with "secondary air pump" or something.

Just thought I would toss this out & see if anybody has any (pertinent)comments to the situation.

- Cam

cdodkin

What age is the vehicle?

Typicaly on vehicles over 5 yrs of age you see the small valves in the secondary air system start to stick. (Due to oil contamination)

These valves control the flow of air into the exhaust system for a cleaner burn - so it's an emissions issue only, not anything that will effect engine performance.

As the valves stick and unstick, the codes for the CEL and come and go.

Remedy is usually replacement of the valves - which are of course a pain to get to!

Hope that helps.

Chris.

ZX9RCAM

I guess year model wouldn't hurt any......it's a 1999 with ~74,000 miles now.

Thanks Chris, that makes sense.....

cdodkin

Yep - you're right in the zone for the valve issue - should get a decent Porsche shop to check the codes when they next pop up - their machine can identify more specifically where the issues lie, rather than the broad brush ODBII codes.

Cost was $600 for a fix last time I had it done, parts and labor (mostly labor)

Chris.

87turbolook911

Timely post as my check engine light came on about two weeks a go and noticed no difference in the car. Had it checked out and the OBD reader said it pertained to OEM emissions control "something". Went ahead and reset the light.

Drove two weeks and the light came on again yesterday. Again...no difference in car performance....didn't get around to reset it. Then this morning I started it up and no CEL?

What you describe below may be what I'm experiencing....

Any DIY directions on checking /fixing the secondary air system?

99firehawk

ok lil misinforamtion going on here.

which faults do you have p0410 p0411 are secondary air faults for both banks
if you have one bank then you have issues, the most likely case of this fault is a vacum leak,
a vaccum leak any where in the system can cause a drop in vacum preventing the full opening of the mechincal shutoff valve hence your faults.

step 1
check your o2 adaaption numbers on a 99 its the tra and fra numbers (you will need a pst2 piwis or im sure the durametric or snapon scaneer can see similar numbers)

if the are positive you have a vacum leak and need to check each component in the system for holding of vacum. start with the vacum canister the tend to crack as they get old

99firehawk

and fwiw I have never seen a bad mechincal shut off valve on a 9x6 car and only 2-3 bad eletrical valves people have no idea how the system works and like to throw lots of parts at hoping something will fix it

an02boxster

99firehawk,
are you saying that if you have p0410 and p0411 it is a different problem than only one bank?

cdodkin

Brad,

appreciate your perspective, but I have had 2 986 cars, one 98 and one 99 where the valve replacement was a permanent fix for this exact issue.

I did have the local independant Porsche shop confirm the fault location using their Porsche diagnostic system before work commenced.

First set of secondary air system valves I did myself, which was a huge pain, took way too long, and resulted in me swearing I'd never do it again!

Second car - I had the independant shop do the work - same parts, same result.

Obviously - as I said - you do need to have a better diagnosis than just the ODB codes, otherwise you cannot be sure exactly where the fault lies.

But based on my experience - the valves have been the issue, and not the vacuum leak.

Hence the advice.

The other point to note here, is that the fault code comes and goes - which indicates a fault which can 'clear' itself.

This is difficult for a vacuum leak to do - but follows the MO for the sticking valves.

My local independant shop confirmed that they see this many times in 'older' 9x6 models.

Chris.

ZX9RCAM

Great info, thanks guys!

If I recall correctly it indeed was both p0410 & p0411.
At one point there were 4 codes thrown...all seemed relatively similar
in description.


Keep it coming..........

1999Porsche911

Often, these codes are caused because the vacuum line from the vacuum reserve is not connected. It can also be an electrical problem with the changover valve, or a bad air changeover valve. The vacuum line for the electric changeover valve is so small that identifying it as a vacuum leak with a vacuum gauge is difficult. You codes indicate that both banks are experiencing probelms so it is probably a single, main componant.

Here is what I would do. Assuming that the pump is working.

With the engine running, remove the vacuum line for the electric changeover valve that goes to the vacuum reserve canister. There should be constant vacuum. If not, the other end of the hose is disconnected and your air changeover valve will not open.

Next, on a cold engine, remove the other vacuum line from the air changeover valve. Start the car, at which time the pump should start. You should be getting a vacuum in the disconnected line until the pump shuts off. If not,. problem is with the electric changeover valve.

On the other hand, you can immediately jump to the end and remove the larger hose from the non return valve. On a cold engine, the pump should start and there should be air blowing out of the hose. When the pump shuts off, the blowing will stop completely and NO AIR should be coming back out of the valve. If this is the case, then you can safely assume that everything before this point back to the pump is working as designed.

The function of the system is simple. There is constant vacuum to the change over valve to which a vaccum line to the air valve is connected. When off, the changeover valve does not allow vacuum to get to the air valve. When on, (pump running) the valve activates and allows vacuum to get to the air valve and allows air to pass into the manifold through the one way valve.

Bad air changover valve is a very common cause.

Here is a writeup on the system:

http://www.renntech.org/forums/index...10184&hl=p0410

Jim

cdodkin

Jim,

great write-up link - absolutely follows my experince, including the frustration and sore fingers!

Chris.

99firehawk

what year is your car ?

410 and 411 means that both banks are not seeing air,

step 1 check your fuses
step 2 make sure the pump comes on when you cold start the car
step 3 your gonna needa vacum pump
check the one way valve small black and white nipple going into the intake note its orentaon and reinstall in proepr direction it should hold vacum one way and allow free air to pass the other
check the vacum canister see if it holds vacum if it does then move on to
checking the electric valve, first jump the conacts with 12+ and ground do you hear it click if you hear it click its probaly good
vacum check the valve does it hold? now apply + and - valve clicks vacum should drop
valve is working properly.
vacum check the changeover valve it should hold vacum

thats about the basics

really easier with a pst or piwis so you can see fuel trim and see if it is a vacum leak 9/10 tiems it is.
secondary air is so often misdiagnosed, I see lots of people shot gun parts onto cars becasue they have no idea how it works or how to fix it. And I stand by my previous statement, i have never seen a faulty changeover valve on a 9x6 car and i assure you I Have seen plenty with those faults

cdodkin

If the fuse had failed, then the code would not reset itself - correct?
If the pump had failed, then the code would not reset itself - correct?
If the vacuum canister didn't hold vacuum, then the code would not reset itself - correct?

The key would appear to be that the codes come and go - suggesting a fault that comes and goes, rather being than a persistant issue.

The CEL is resetting itself, it's not being reset by Cam.

Or am I missing something?

So an intermittant issue would tend to suggest sticking or faulty valve(s), rather than any of the above.

But then I'm biased because I've had two out of my three 9x6 cars have this issue when they've reached this sort of age / mileage, and I have no clue how the magic tubey bits around the big mechanical whirry thing work.


Cam, let us know if you get this one fixed - and if I've wasted my money shot-gunning parts into my cars to fix my problems.

I can then pass the bad news on to Sid and Jim as well.

Chris.

ZX9RCAM

Thanks Brad & Chris,

Yes the codes are resetting themselves....I am not doing it.
The light STILL is off so we will see what happens in the future.

Thanks again for the time spent!!

- Cam



ps....If you are asking me, the car is a 1999 C2.