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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 03-16-2009, 09:23 PM   #1
beberle
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Secondary Air Pump Troubleshooting DIY

I've been getting 'secondary air flow system too low' codes from my 330i. I thought others might benefit from my journey.

What does the Secondary Air System do? It's for emissions. On a cold startup, the engine is running rich until the O2 sensors can heat up. In order to meet emissions and not foul the cats, air is forced into the exhaust to 'lean' it out until the engine warms up (about 60 seconds).

1st step- verify the secondary air pump blows air on a cold startup. Remove the clamp and hose from the pump. It's the charcol canister-looking-thing right up front on the passenger side of the engine bay. There is a 1" hose coming from it to the Secondary Air Valve on top of the header. This thing really BLOWS on startup. THe car must be cool/cold or the pump relay won't trigger. Mine worked fine.

2nd step- verify suction at the secondary air system valve. Pull off the suction line at the valve and have someone start the car. There needs to be suction in the line to open the valve on the exhaust that allows the forced air from the pump into the exhaust. This seems to be a common problem- cracked suction line anywhere from under the intake manifold to around the side of the valve cover. My hose looked good and was providing good suction.

What next?? The valve is supposedly another common failure point. It gets cooked by the exhaust and sooted-up. Should the valve fail in the open position, it will allow exhaust gasses into the air pump and destroy the air pump through heat and moisture. I tapped on the valve and grabbed it just for the heck of it... I was giving up. What's this?? Something wrong w/ the air hose on the back side next to the valve.

I removed the hose from valve and found a big hole melted in it. That would explain the 'air flow too low' codes. I duct taped it up for a temp fix just to make sure the CEL stays off while the new hose comes in. As far as I know, this is the 1st bad Hose in the Secondary Air Flow system reported. Definitely a cheap fix considering the air pump is $250 and the valve is $100.


1st pic: the air pump above and the valve below
2nd: That's what I call a bad hose. The hole was facing down; couldn't see it.
3rd: Duct tape rules! As long as it doesn't catch fire...
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Last edited by beberle; 03-18-2009 at 10:22 AM.
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Old 03-16-2009, 10:57 PM   #2
JZMC
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I have the exact same problem.
Just happened last week.
I got the peake tool and it told me immediate it was the secondary air flow low.

I havent checked the hoses, but I am looking at the air pumps, I see there might be two variants.
http://www.realoem.com/bmw/showparts...88&hg=11&fg=50
http://www.realoem.com/bmw/showparts...15&hg=11&fg=50
Can anyone confirm that those are two different pumps or it is just that one has a lid on it?

Thank you,
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Old 03-17-2009, 05:18 PM   #3
Xelo
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Yes, there are two versions of the pump.
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Old 03-18-2009, 10:24 AM   #4
beberle
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2 days now and the duct tape is holding fine and no Check Engine Light. New hose should be in tomorrow. Pelican Parts comes through again
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Old 03-19-2009, 02:01 AM   #5
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see my pump is working, the valve beside the pump on the manifold has suction....but im still throwing the codes for Secondary air system flow too low on 1-3cyl & 4-6cyl....what now? Is there a DIY from that point on?
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Old 03-19-2009, 07:29 AM   #6
beberle
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My next step was going to replace the valve. From what I've read, it's a fairly common failure point. They usually fail 'open' and cook the pump. Maybe they can fail 'closed' or just get too built up w/ carbon? If the $12 hose wasn't going to fix my problem, I was going for the $100 valve.

Please post whatever you do so that we can learn!
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Old 03-19-2009, 09:20 AM   #7
dirtbiker245
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Thats weird for the hose to have melted like that. Is your motor still running the stock exhaust manifold gaskets that have the heat shield looking thing on it?
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Old 03-19-2009, 09:41 AM   #8
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Quote:
Originally Posted by beberle View Post
2 days now and the duct tape is holding fine and no Check Engine Light. New hose should be in tomorrow. Pelican Parts comes through again
Good job on saving $350. I wasn't as lucky as you...
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Old 04-12-2009, 06:42 PM   #9
JZMC
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Found this link in an old thread.
Definitely an important diagnostics

http://www.bavauto.com/newsletter/20...newsletter.pdf pg 6 & 7
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Old 04-13-2009, 09:53 AM   #10
ThatGuy_JZ
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Quote:
Originally Posted by germnblt View Post
see my pump is working, the valve beside the pump on the manifold has suction....but im still throwing the codes for secondary air system flow too low on 1-3cyl & 4-6cyl....what now? Is there a diy from that point on?
replace the $15 dollar salmon colored relay!!

on mine everything tested that it was working fine, but every now and then randomly it wouldn't and would trigger the light back on. Ever since I replaced the relay months ago I haven't had a problem
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Old 04-13-2009, 06:10 PM   #11
DonovanM
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Crazy! I had the same problem just recently. Different engine too, M52TU - but probably the same hose (which was discontinued and replaced by a new PN#).

Mine never threw an SES light, I was just poking around my engine bay and noticed a frayed hose and wondering WTF it was for. I just replaced the hose, the rest of the system appeared to be working fine (was circulating air just fine).

The only thing I may have noticed (and this could be completely wrong) is that my car smokes less on cold startup, which would make sense if air wasn't getting pumped in there before and now it was.
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Old 04-13-2009, 06:30 PM   #12
Wraisil
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There is a smaller hose that heads back to the back of the engine and to an electric valve under the intake. Mine was completely broken off and brittle, might check that one. Runs by the 02 sensor wire harness and back from there
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Old 04-18-2009, 08:38 AM   #13
jaymiany
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this problem happened to me i just went to autozone and got a heater hose for $1.75 cut it the same length and just put it on. working fine.
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Old 05-09-2009, 04:19 PM   #14
AVR2A
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I just did my oil change and as part of the reset I always check for codes. I don't have a light on, but did get code 19-F6 secondary airflow too low on #4-6. I did a cursory check of the hoses but they seam ok; the one from the pump to the vale is definitely soft though. Any idea what would cause just F6 (without F5)? I would expect if it was a bad pump/valve I'd get both?
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Old 05-11-2010, 07:52 PM   #15
redwood77
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Quote:
Originally Posted by ThatGuy_JZ View Post
replace the $15 dollar salmon colored relay!!

on mine everything tested that it was working fine, but every now and then randomly it wouldn't and would trigger the light back on. Ever since I replaced the relay months ago I haven't had a problem
what is the salmon colored relay? i keep getting these codes ('secondary air flow system too low') despite replacing the same hose as the OP (mine was badly disintegrated) as well as some of the vacuum line that attaches to the valve. i wonder if more of that line might be degraded where it disappears towards the back of the engine (i don't know how to get back there). in the meantime, i thought i'd replace this relay for $15 if i could figure out what it is ...

thanks
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Old 05-11-2010, 09:29 PM   #16
JaySpec
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bump this thread good infomation will review it later
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Old 03-13-2011, 03:27 PM   #17
moiz21
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Quote:
Originally Posted by AVR2A View Post
I just did my oil change and as part of the reset I always check for codes. I don't have a light on, but did get code 19-F6 secondary airflow too low on #4-6. I did a cursory check of the hoses but they seam ok; the one from the pump to the vale is definitely soft though. Any idea what would cause just F6 (without F5)? I would expect if it was a bad pump/valve I'd get both?
Sorry to bump and ol thread but just got this code today after light came on the dash. And no one answered this, so hoping someone can give it a go and help me with this issue Thanks in advance guys.
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Old 03-16-2011, 05:13 PM   #18
nborton
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Even though this is an old thread. It's got some great advice on the hose. I've had the same codes for a little while. I knew what it could potentially be, but I didn't have the time to do anything about it until recently. Ends up mine is just like others on here. The hose has cracked, or more like melted from heat over the years.

Check the hose first. Cheapest and easiest potential problem to fix.
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