secondary air system flow - BMW Forum

whosyadadie01 · 01-08-2008, 03:31 PM

while reading the codes on my 96 328i auto, i got the following codes.

catalyst efficiency below threshold cyl 4-6
secondary air system flow to low cyl 1-3
secondary air system flow to low cyl 4-6

any idea on what could be causing these problems would be very helpful as i dont no where to even begin.

dvmotorsports · 01-08-2008, 09:36 PM

Quote:

Originally Posted by whosyadadie01

while reading the codes on my 96 328i auto, i got the following codes.

catalyst efficiency below threshold cyl 4-6
secondary air system flow to low cyl 1-3
secondary air system flow to low cyl 4-6

any idea on what could be causing these problems would be very helpful as i dont no where to even begin.

with out getting any more info, i'd say faulty cat or O2, and faulty or intermittent secondary air pump operation.

AlpineSixAndSeven · 01-08-2008, 10:22 PM

could just be the air pump..... maybe causing the cat to error?

dvmotorsports · 01-09-2008, 12:03 AM

Quote:

Originally Posted by AlpineSixAndSeven

could just be the air pump..... maybe causing the cat to error?

probable. depending on when the vehicle throws the code. if he clears it and cold starts the vehicle, and it throws a fault, i would place blame solely on the pump. to the best of my recollection, the secondary air pump it start up operation only. i have been wrong before. but if it throws a pump code and after driving for awhile throws the catalyst code, then it is obviously a different issue.

self explanatory I know. just felt like sharing.

on the other hand, it states this

catalyst efficiency below threshold cyl 4-6
secondary air system flow to low cyl 1-3
secondary air system flow to low cyl 4-6

theoretically it should fault both cats

AlpineSixAndSeven · 01-09-2008, 12:23 AM

yeah... maybe that cat is on the way out... and the other is in better shape???? Maybe fix the pump issue then clear the codes.... and see if the cat error codes up again......

Dirty_Tool · 01-09-2008, 12:39 AM

try tapping on the cat with a rubber mallet and listening to see if it is coming apart on the inside.

dvmotorsports · 01-09-2008, 01:00 AM

how many miles do you have?

dvmotorsports · 01-09-2008, 01:01 AM

Quote:

Originally Posted by AlpineSixAndSeven

yeah... maybe that cat is on the way out... and the other is in better shape???? Maybe fix the pump issue then clear the codes.... and see if the cat error codes up again......

exactly. because, the pump can cause a kitty fault but not the other way around. it's possible that the cat fault is erroneous and just there due to the pump failing.

AlpineSixAndSeven · 01-09-2008, 01:13 AM

^ That is what i thought.... maybe the secondary pump effects cyl 4-6 more?

dvmotorsports · 01-09-2008, 01:51 AM

I'll have to ask at the shop tomorrow.......if i remember

AlpineSixAndSeven · 01-09-2008, 02:38 AM

^ lol we never do......

whosyadadie01 · 01-09-2008, 07:40 AM

thanks guys for all the answers:

the car has 156k miles on the clock

i just replaced both bank 2 o2 sensors with oem from the stealer

ill have to get under my car on a nice day and tap the cat to see if anything rattle's around.

dvmotorsports... if you can ask the shop then that would be great.

ive herd a few things about the secondary air pumps, but never herd of them going bad and even less of when they turn on.

ill have to clear the code's and cold start it later and see if they come back

dvmotorsports · 01-09-2008, 04:08 PM

okay, i spoke with one of my shop master techs today. he happened to have a secondary air pump from an e36 under his tool box. the reason there is no second cat code, is because the second cat is not monitored in that fashion. he said what usually will happen is that the rivets in the plastic cap will break or deform causing little or no air flow due to a leak in the pump. there in lies your problem. the other possibility is that there is a vacuum leak in the hose on the pump. check the hose first. it should be one or the other. change it and you should be good. hopefully its the hose (i'm sure it's a cheaper repair)

good luck

AlpineSixAndSeven · 01-09-2008, 05:19 PM

^ nice hopefully it is just the hose

whosyadadie01 · 01-09-2008, 10:20 PM

thanks for the response ... i really wouldnt be surprised if it is a leaking hose, ive been trying to replace the leaking hoses for a while now.

ill start with checking the hose and see where that gets me and let you guys know how it goes