99firehawk

the code could reset itself with a vacum leak, depedning on conditions temperature ect.
if you get in the car and go before the secodary air is done running it will abort and not throw and faults and possibly shut off the lamp

also if your car is an 01 it could be as simple as a reflash of the dme there was a bulletion on that 0303

cdodkin

It's a '99.

I'll be interested to see if the self healing vacuum theory holds water - or should that be air!

Chris.

1999Porsche911

A vacuum leak "anywhere" in the system (short of the SAI lines being totaling disconnected) will not cause the system to malfunction and therefore correcting the leak will not fix a problem with the system. The air changeover valve is operated on a low vacuum of 5 in-hg. If your car had a vacuum leak that reduced the engine vacuum to that level, the engine would not even run.

Additionally, simply because you have a high negative or high positive LTFT does not mean you have a vacuum leak or that anything is even wrong with your engine. Identifying a vacuum leak by looking at the fuel trims is, at best, a guess and there are much better and easier ways to determine a leak. Even your STFT will balance out when the O2 sensors activate, eliminating any suggestion of a general leak. Fuel trim is only an indicator if you have a baseline of readings for that specific engine. as many engines run normally with a high positive or negative LTFT..

Projekt EPiK

I'm pulling this one back from the dead bc, well..I have a 99 C2 6mt that is displaying these codes (0410, 0411) along with "signal implausible" after each code, on my Durametric. The SAI has been replaced with a new to me one, 86k miles, but it was clean and spun smoothly. Testing the plug into the SAI what signal am I looking for? I'm not getting any voltage at all on either terminal when the car is cold started. I had a slight water incident a few months back, dipping the back left corner in a gully, water did cover the SAI and rusted it inside.. could the changeover valve have fried? Where is it? Searched first and it brought me to this thread.. lets get some new info going

3/98 Carrera2 204,850 miles.. original

F-Lambda

There's a thread on this topic here . I had the same codes last fall, in my case it was the changeover valves.
If you trigger the SAI pump with the Durametric and don't get any action, I'd look at whatever that has for a fuse (and maybe a relay) - it uses a lot of power.

Projekt EPiK

I checked every single fuse under the dash, no response when triggering with the Durametric. Any tips on where to find the relay in the car? Or possibly a hidden fuse box.. there was no fuse indicated for the SAI system that I could find.

F-Lambda

Behind rear seats? I didn't have to go there. Relay 99965701790 is a bargain too!

theprf

There's a 40 Amp Maxi-Fuse in the rear relay panel, yes, behind the seats & under the carpet. The relay is there too.

Projekt EPiK

located that big honkin 40a fuse..blown wide open, probably right after my SAI pump locked up. Replaced it, and successfully activated SAI thru the Durametric! I hooked up the old frozen up SAI (that I had stripped down and rebuilt) and it worked too.. now I have a spare I guess