Engine Diagnostic question - BMW Forum

tiremann34 · 08-09-2004, 04:53 PM

I had my check engine like go on today

ghead. So i had my coworkers hook up the diagnostic machine to it and it pulled up 12P421 and 12P423 And i looked them up on the internet and it said something like "Secondary Airsystem Bank 1 and 2". I have no idea what the hell that means so if someone could help me out on that i would be very thankful.

97alpineM3 · 08-09-2004, 06:22 PM

Well... the secondary air system.... is your exaust... and your primary air system is your intake....

I would check all of your exaust pipes and joinings to make sure the gaskets are not rotted or gone bad. Other than that... the description of the code is rather vague... so I dont know.

chungaa1 · 08-10-2004, 04:04 AM

any other associated issue along with it?? ie, cruise control went out?

fuel running rich??

maybe it's your o2 sensor
i put on a new o2 sensor on my 1993 325i, it was only llike $50 bucks, and i bought i special socket for it..

ur car may have more then one sensor.. so yeah.. do more research first...

schilke · 08-10-2004, 07:14 AM

Wow these are helpful posts. (Sorry I'm in a pissy mood today.)

I am guessing your car is an OBDII system from the codes...

Your secondary air system is the air pump. It is located in the passenger side corner of the engine bay near the windshield. It comes on when you start your car for a few minutes to help light off the cat.

Have someone turn your car over and listen. Does it turn on? If not, you need a new pump. If it does, then chances are you need a new vacuum valve. I will have to get a pic of an engine bay to point to this crap.

Secondary exhaust

tiremann34 · 08-10-2004, 12:18 PM

ghead son a bitch i wish i had thought of that i heard noise coming from that piece of shit earlier. i hope it is not expensive.

used

schilke · 08-10-2004, 01:59 PM

:lol:

Yeah, good luck with that... $350-$500....

And that's just parts...

97alpineM3 · 08-11-2004, 09:03 AM

schilke.... it was a generalized answer. Pertaining to an exaust code. I was merely giving some knowledge...

As for it quoting what I said in another topic... get over your self. Knowledge is knowledge. If you have a code for a secondary air problem there is more than just two explainations for that. Yes you have an air pump.. you also have a charcole canister that could lose pressure due to a leak from a vacume hose and or cracked lower ring. You could also get air traped in in the import side of your first vacume valve after the pump. Thus not allowing air to circulate. Next.. there is a re-occuring problem with the difference between an exaust manifold leak; as in a failed exaust gasket either between your headers and your cat, or your headers. AND a loss of pressure in cylinders 1-3 and 4-6. It all depends on which one your OBD picks up first. So if your getting a "Pressure low in cylinders 1-3 and 4-6" then it is one of two things. First it could be either that your vacume valve is stuck closed not allowing a push/suction of air to vent and be pushed... or you have a leak in your exaust manifold and or your gasket between your cat and header. The exaust system codes for e36s are some of the more confussing codes to get because if something does happen and you get a code it is often hard to pinpoint what went wrong or what is going wrong due to the fact that if one thing fails in your exaust system... another thing will very quickly fail or be tricked into failing.

If you ask a generalized question... you will most likely get a generlized answer.

I have nothing against you schilke, just please watch what you say in post because people get offended very easily... keep up the good work and passing knowledge.

Please correct me if I missed something or am wrong in any way. Thanks.