Gents,
My 2001 911 C2 has been running great all winter but now have swtiched over to more AC related driving now that Houston is warming up. I got a check engine light yesterday afternoon leaving work. Used the Durametric to identify and clear codes:
PO139 - Sensor ageing behind cat conv cyl 1-3
PO410 - Secondary air injection system cyl 1-3
P1411 - Secondary air injection system cylinder 4-6

Has anyone seen this combo before? Suppose i need to clean/replace the air intake filter?

 

Has nothing to do with the air filter. Secondary Air Injection (SAI) system pumps air into the exhaust system to "light the cats" at first cold start (it's an emission thing). The faults with the SAI system should be explored before condemning the O2 sensor(s). The SAI pump is in the engine compartment drivers side. Does it run and make a vacuum cleaner sound when you cold start the car?

 

I didnt notice anything running yesterday when leaving the office. I normally hear something running when i'm at home, taking my time starting the car up. More of a high pitched noise but i def hear something that sounds like air flowing or being pushed at a high rate.

 

Clear the codes. You can use the activations part of Durametric to activate the SAI pump and see if it runs. Then drive and see if the codes come back.

 

I agree this is a sai issue not o2 performance. Either the pump or change over valve is bad.

 

That's super helpful gents, will try it with the durametric when i get home tonight. Thanks,

 

Think i can find the pump but where is the change over valve located? I saw that Pelican sells the change over valves but didnt see the actual pump listed.

 

Its kinda behind the alternator. There r some simple tests that u can do with the durametric. Basically command the pump to turn on. If it doesnt u need to check for voltage and go from there. If it turns on then u need to check the change over valves and vacuum hoses. Do the diagnostic work....dont just throw parts at it.

 

Right on! thanks....

 

The SAI check valves fail and when they do, they fail in a way that prevents air from the SAI to getting into the exhaust manifold. In the 2001, it is a two part valve. In the update it is one. As it has been said, it is behind the alternator. It was originally a two part system. Now a one part https://www.pelicanparts.com/More_In...M&KeepHeader=Y

You have to remove the alternator to get to it. I don't have the time now, but there is a definitive test for failure of the check valve. I will try to get this on here in 24 hours.

 

That would be awesome, thank you!

 

Remove the alternator.
Apply 12 to the air pump, left side of your engine bay. See if air is coming out the output side of hose 14.
Do a smoke test on the vacuum line 12. If there is a leak, fix it.
Apply vacuum using a hand pump to the vacuum port of the control valve, number 11. See if air is coming output side of hose 10.
If air is coming out of hose 10, and you are getting those two error codes, then valve 9 is bad. Change it.

 

Thank you for sharing the diagram. Super helpful....