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Ok guys, now that this seems sorted out. In my case the problem was a faulty air change-over valve. Since I was at it I also changed the electric change-over valve. I thought I'd post an entire post-mortem on the whole incident. This way future reader can get all the info in one spot. In short, no horror stories but a lot learnt. A Huge thanks to Loren, 1999Porsche911 and tholyoak for helping me thru this. Guys, I'm going to be quoting you in the writeup below, hope you guys don't mind. If people want to read the original message and the whole thread, its below. Background ============= I got the P0410 ("Secondary Air Injection Malfunction") and P1411 ("Manufacturer Control Auxillary Emission Control") along with a Check Engine Light (CEL). What is means =============== During a cold start the catalytic convertors don't work very efficiently because they are cold. To compensate for this there is an air pump which adds air to the exhaust gases so the cat's behaviour can be somewhat compensated for. If you get this error that additional air isin't being mixed with the exhaust gases. No vehicular damage (CEL shouldn't be blinking!) but your emissions care higher during every cold start. What to do next (if you plan on fixing it yourself) ================================ 1) Observe the connection below 1 - Secondary air injection pump 2 - Air change-over valve 3 - Electric change-over valve 4 - Non-return valve 5 - To the cylinder heads 6 - Vacuum reservoir 7 - To the intake air system Basically 1 pumps the air thru 2->4->5 and reaches the exhaust gases. The computer controls when to start the blower and also when to connect the air link by controlling #3. When #3 is "ON", the vacuum line is connected to #2 which turns #2 "ON". Then #2 will connect the air blowing from one pipe thru to the other pipe. You should check every component in that chain starting from the easiest to check to the most difficult. 1. Check Air injection pump (#1, ~$430) ============================ - Do a cold start, the secondary air pump should run at least 30 sec (or more). - Sounds like a small vacuum cleaner/touch it to feelt it hum/pull off the larger hose to feel it blow air - If the pump "fails", here are the reasons : A.) "Check the electrical connections and fuse (40A fuse on the relay board next to the DME), and the relay (position 10 on the same board)." - Loren. B.) If the fuse seems ok its possible the pump is dead (you did test this with the car cold - cold start , right ?). TIP: Before buying a new pump ($$$) you could take it to a porsche dealership and have him quickly/freely verify this for you. If your air pump works, then you need to check #2 and #3. Both of these are deep inside the engine bay. You MUST remove the alternator before proceeding. Please read that thread on alternator removal - you will save several hours of frustration and sore fingers if you read before you work ! Once you remove the alternator (aka generator) you should see this ... its basically the same system shown in the black/white diagram above but this is how it looks in real life. NOTE-1 : Please note the existing connections on the tubes before you rip everything out. A camera/camera phone comes handy. NOTE-2: For the steps below, make sure you DON'T let the tubes/pipes slide away into the inaccessible areas of the engine bay - they are a HUGE pain to bring back if they slip away (unlikely-but you're warned!) NOTE-3: Finally, if you've opened the whole thing till here, I'd suggest you test both #2 and #3 to be sure you catch every failed part in that system. I simply replaced both with new parts even thought only #2 was bad in my case - #3 was just another $20 ! 2. Air change-over valve (~$80) ====================== - Note existing connections - Use nose pliers and slide the ring-clamps away from the valve onto the respective rubber hoses. - Take the little pipe off - Remove the valve piece out of the engine bay -> clean it with some alcohol wipe (don't drench it in any weird clearer/liquid - you're just sanitizing this for the next step). - Wash and clean your hands (Yes!) - Suck air out of the little pipe and quickly put your finger on it (to maintain its low pressure). If this is tough, ask your significant other (chances are they'll go "eeeeks"). - If you find you cannot maintain a low pressure on the little pipe (i.e. it feels 'open' when you suck out the air) then your valve is bad. - This low pressure should open the valve and you should be able to blow from one pipe (coming from the air blower) thru to the other. - If you cannot blow thru and are sure the low pressure is maintained, you again have a bad valve. 3. Check the Electric change-over valve (~$20) ================================= These are triggered off a 12 V supply. The valve has (+) and (-) markings for polarity of the electric connector. I quickly rigged up a 12 V supply by cascading a 9V battery with 2x 1.5 v batteries, some duct tape and some wiretags/wires. If your physics is rusty, this is the connection figure. (-A)---(-)[9 volts](+)--(-)[1.5volts](+)--(-)[1.5volts](+)--(B+) Between (-A) and (B+) you have 12 volts ! - make a note of existing connections - remove the valve from the engine bay - Connect the wires coming out from A and B to the electric change over valve's connection - If you've got a working valve, you will hear a click sound when the valve triggers. - Now, also blow from one pipe (after wiping it with an alcohol wipe!). - you will be able to blow thru/NOT blow thru as the valve opens/closes as you connect/disconnect the 12v supply wires. TIP: Check #2 also and if ONLY your electric valve(#3) is faulty, you could test the "FALSE HIT - valve from another system" valve similarly. If this "FALSE HIT..." valve works, you could swap it with #3, reassemble the car and drive ! The benefit ? The "FALSE HIT..." valve is accessible without _ANY_ disassembly and you can replace it some other day under 5 minutes when your replacement valve arrives. Also, no harm if the car is driven for the time being with that valve being faulty. Hope this helps ! Cheers! Sid -----<original post below> -------------------- Well, I got a CEL last night. So I stopped by Autozone and borrowed their OBD2 and got the following ... 1) P0410 : "Secondary Air Injection Malfunction" 2) P1411 : "Manufacturer Control. Auxillary Emission Control" My car = MY99 996 C2, North America. I saw some other posts on P0410 and today morning checked the air pump on the left side/driver side of the engine compartment near the tail lights. It seems to be working in that I could hear it buzz like a mini-vac. Not sure exactly part was making that sound, I also touched it to feel it vibrate (just like an electric motor should). I quickly glanced to see if the rubber hose on the pumps lower-back-right end was still connected and visually it looked ok. I'll have another closer look later (was behind schedule this morning!). Do you guys have any good pointers on what next I should do ? FYI, I have modified my stock exhausts with a regular bypass pipe, fabricated along the lines of the PSE version2. It sounds great and there hasn't been a change in the exhaust note since then till now/CEL coming on. I don't think its related but I thought I'd mention anything exhaust in this post. Thanks in advance guys ! Sid PS: I just got my customised plate .... SIDS 911 :D ... (actually SID5 911)