aracer

cannot seem to find any info on this system and would like to know how it operates.....any chances of that-I have DTC 401 and 402 indicating poor flow...cannot get it by NYS emmisions. NO check engine lite, just will not set monitor for secondary air injection

Macster

Secondary air injection systems are similar. Briefly under certain conditions at engine start (engine cold is one) the pump is turned on and an electric switch is activated that lets vacuum open a valve that directs the air provided by the pump into the exhaust ports. There is upstream, downstream and atmosphere, but generally there is just upstream and atmosphere (and the pump's off in the latter case).

Assuming the pump comes on when a cold engine start is executed, the pump will run for a minute or so (depends upon temperature) supplying extra air to the exhaust system to help the excess fuel burn in the converters and warm them up faster so they can process exhaust gases (the converters need to be hot to do this).

As soon as the converter temperature is on target or the signals from the 02 sensors that monitor the converters indicate the converters are functioning the air injection pump is turned off. The engine controller will go closed loop at this point or very shortly thereafter.

Statically, all you can do is trace/follow the air hose from the pump to the valve and verify the hose is intact and has no breaks or is loose.

There electrical tests you can do -- with the right break out box -- to test the switch's electrical operation and that it has the right vacuum. I have some of these for another model of Porsche. None for the 997 GT2/GT3 though. The tests might be the same they might not be.

From the switch you want to follow the lines that route the air to the exhaust port injectors making sure these lines are intact, properly connected, not pinched, etc.

In the 993 model there was a problem with the secondary air injection ports getting partially blocked from carbon to the point air flow was restricted and in '96 and newer 993s this would set the check engine light.

I have not heard of any build up reports for the 997 engines.

Obviously because of poor flow the secondary readiness monitor is not being set to complete. The engine controller has a way of verifying the proper amount of air is being injected and if it is not then the readiness monitor will of course not be set to complete.

Some states, but not all -- maybe your's one of the exceptions -- will still pass a vehicle even if one (or more) readiness monitors are not complete. (CA will allow 2 incomplete but I do not recall if there are some that *must* be complete or if any 2 incomplete is accepted.)

Bear in mind that even if the system is working perfectly, when you clear any DTCs (diagnostics trouble codes) all readiness monitors are set to not complete. It takes a bit of driving (not just engine idling) to have the engine controller have sufficient time to set the readiness monitors to complete.

The secondary air readiness monitor though may not require much driving. The engine controller may flag it complete after a cold start if of course the engine controller detects sufficient air being injected.

Sincerely,

Macster.

aracer

the later cars have a few alternative secondary air injection systems depending on type and model. SINCE THE SCUM THAT PORSCHE CONTINUES TO BE, in terms of diseminating proper current workshop information on current models, I have a hole in info system on this subject. there does not seem to be any "vacuum" initiation. the pump simply starts at the right time and forces the air through one way valves on the GT3 model. The monitor issue (as usual for myself) is a unique failure. Of course I always get the easy jobs!!!!!-will post upon proper resolution of inspection problem---thank you so much for the time you spent on answering to my delema. M