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Discussion Starter #1
Hi,
A month or so ago check engine light came on in my 318is (4 cyl), and at the dealership they told me it's like $400 and that it had do with the exhaust/polution, whatever, and that I don't really have to fix it. I didn't, cos I knew I had to do a mandatory emission test a few days later. The car passed with flying colors, they even told me my emissions were "excellent". So, of course I didn't fix the thing.

Cos my Check Engine light has been constantly on since, I got the reset tool from Peake research, and it reported TWO fault codes, so I'd like to know if anyone knows what they are, and how serious it is. Cos back at the dealership they only told me there was one problem, so I'm wondering if these two are combined, or if a new one popped up in the meantime. Other than Check Engine light, the car behaves perfectly, a few weeks ago I even had a 1500 mile trip.

I am quoting the code faults from the manual:

1. "Fuel trim, QL additive"
2. Secondary air control

Thanks.
 

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What car do you have? I can help you pinpoint the problem if you can tell me if you have a 4 or 6 cylinder.

1. The fuel trim faults indicates either a lean or rich mixture. The computer is compensating the fuel trim (adding or taking away fuel) to keep it in a normal range. This fault is stored if the parameters are out of line. It is likely a lean condition caused by a vacuum leak somewhere, and the computer is adding more fuel than normal.
It is likely that this fault was NOT stored when the dealer looked at it, because this is a problem that should be fixed.
2. Secondary air is a common problem. This is however, NOT an important system as far as engine performance is concerned. What it is, is simply an air pump, and a couple of valves. On a cold start, the pump comes on and blows air into the exhaust system. The added oxygen helps heat the catalytic converter up faster, so it will function. That is all it does. If the oxygen sensors don't pick up the added oxygen from the pump, it stores this fault. Usually the pump goes out.

If you have a 4 cylinder, look at the vacuum line right above the oil filter housing. If that line is cracked, which is common, the secondary air valve will not open, and it will also cause a lean condition. So, your problem might simply be that vacuuum line for BOTH of the faults. The next item to check on the 4 is the PVC valve, on the backside of the intake. Spray some wd40 or brake clean around that area and see if you pick up a vacuum leak.

Hope this helps. :thumbs
 

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Discussion Starter #3
TECH: Thanks a lot. Yes, it's a 4cyl. 318is.

I will experiment more now that you say problem #1 is important.

Thanks.
 

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TECH: Another, follow-up question. :) If I (or dealer) fix #1, and I'm left with #2 only (secondary air), is there a way to have the damn check engine light NOT come on for it all the time? You see, I got that diagnostic tool, and it's cool 'cos it can reset the check engine light. But, if I never fix the secondary air problem as it is not important, then check engine will always be coming back on, arrrgh. So I will have to be checking with the tool very often to see if it's just that problem that check engine is reporting, or if maybe there is a new one, as well.

Also, what's your guesstimate the dealer will get from me to fix #1?

Thanks.
 

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Originally posted by clickboom@Jan 14 2004, 01:11 AM
TECH: Another, follow-up question. :) If I (or dealer) fix #1, and I'm left with #2 only (secondary air), is there a way to have the damn check engine light NOT come on for it all the time? You see, I got that diagnostic tool, and it's cool 'cos it can reset the check engine light. But, if I never fix the secondary air problem as it is not important, then check engine will always be coming back on, arrrgh. So I will have to be checking with the tool very often to see if it's just that problem that check engine is reporting, or if maybe there is a new one, as well.

Also, what's your guesstimate the dealer will get from me to fix #1?

Thanks.
There is no way to keep the light off. Every time the system checks itself, it'll throw the fault.

As for cost of repair, it depends on what the problem is. If it's just a vacuum line, you can easily fix it yourself. The main one to look at is right above the oil filter. Check both ends of that line.
 
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