As my title says, mom's 2003 525i wagon failed smog yesterday with the diagnosis that the Secondary Air System (SAS) is at fault.
The tech at Pep Boys stated that if the car isn't driven much there may not be enough data in the system for the SAS to give any readings, and she doesn't drive much... They also said it threw no error codes and the CEL is not on.
I do have a code reader which I have not tried yet, but which I can do today when I pay her a visit. Anything in particular I should be looking for? I plan to take readings before and after a long drive just to verify their assertion that there are no codes showing.
I did some research here first and found this thread: https://www.bimmerforums.com/forum/s...amous-Fuse-107!
At least with the wagon I apparently don't have to take out the front passenger seat to check the fuse!
525i-smog-test.jpg
Last edited by LysanderSpooner; 06-15-2019 at 11:57 AM.
Read the car with INPA and report all codes.
Have you either recently had the battery disconnected or had repairs done where somebody might have reset your monitors? I recently had to repair a smog related issue and after resetting the monitors it took a bit of driving to get all of them to set. In my case I did have a code to go off of prior to the repair. There is a drive schedule you can do to get the monitors to set, but I've always found normal driving for a week sets them.
What kind of code scanner do you have? Are you able to look at the emission monitors?
We did have some paint and bodywork done a few months back and at that time they may have disconnected the battery. I would be surprised if she has put 300-400 miles on it since then. She only drives a few times a week, and mostly short trips around town.
I don't have the code reader handy at the moment, but from what I recall it's rinky dink little dimestore jobby if that helps... ;-)
I had a similar problem with my '02 money pit, err, 525i. I found a wonderful article on e46fanatics, I think.
Anyway, the upshot is that you probably have a "lazy" O2 sensor. When bringing my OBD II monitors to ready, the Cat monitor took a long time to set, and the secondary air never would. I found that the upstream sensors are looking for a slight voltage drop when the air pump kicks in. If the sensor is "lazy" the O2 monitors will eventually come ready but the SAS will never set because the computer can't see this slight, rapid, voltage fluctuation as the air come on.
So, to correct, first make sure your pump is working. From a cold start, have your air pump hose disconnected from the valve and see that it puts out a strong stream of air. If not, bad pump.
Next, at any engine temperature, disconnect the air pump and the vacuum hose from the secondary air valve. Start the engine. Then, using a MityVac, or equivalent, apply vacuum to the vacuum nipple. The valve should open and close. You'll be able to tell because you'll hear the engine noise from the valve change tone. Louder when open, quieter when closed. If that doesn't work, defective valve.
Next, with cold engine, connect the air pump to the valve and disconnect the vacuum hose from the valve. Attach a vacuum reader to the hose and start the engine. You should see 10 or 12 inches of Hg. If not, you have a bad relay valve at the back of the intake or a cracked/broken vacuum hose somewhere.
If you've passed all these simple tests, then it's one of the upstream O2 sensors. In my case, one appeared to be older than the other, so I replaced the older one and the problem went away immediately. The Cat monitors set very quickly after that, too. The Secondary Air monitor should set in just a couple cold starts.
Pep Boys is basically full of it. As I said SAS will set in 2, maybe 3, cold starts. 300 - 400 miles is plenty of driving to get all the monitors set. But, again, long driving does nothing for secondary air. The computer only "checks" at cold start. If it doesn't come ready that start, it won't try again until the engine is cold. Frankly, I wouldn't let Manny, Moe or Jack near any of my cars. My extent of using them is to order tires from TireRack.com and having PB mount/balance them.
Last edited by E39 Newbie; 06-15-2019 at 04:30 PM.
Current stable:
2002 525i (Daily Driver)
1994 SN95 Mustang 'Vert (The Bumblebee)
2001 325i Convertible (Beach cruiser project)
"Dime Store" code readers are just fine for determining OBD II status, and reading basic OBD II related codes. It will do nothing for the bazillion-and-one other codes these things throw.
Current stable:
2002 525i (Daily Driver)
1994 SN95 Mustang 'Vert (The Bumblebee)
2001 325i Convertible (Beach cruiser project)
I had to emissions test my '98 750iL E38 and the first time I had a bunch of stuff "Not Ready". The tech told me to drive the car mixing up street and freeway driving for a couple of hundred miles. Did that, went back and all the "Not Ready" sensors were "Ready" and I passed emissions.
Give it a shot.
Mike Drives:
BMW's
E24 - 635CSiA - (1) 1985 (US)
E24 - 635CSi - (1) 1985 (EC)
E31 - 850iA - (1) 1991 (Black)
E31 - 850iA - (1) 1991 (Calypso Red)
E32 - 740iA - (1) 1994
E32 - 750iA - (1) 1990 (Not an "L") (EC German National)
E32 - 735iL - (2) 1990
E32 - 750iL - (1) 1990
E38 - 740iLA - (2) (1) 1997 & (1) 1998
E38 - 750iLA - (1) 1998
E38 - 740iA - (1) 2000 "Short Sport"
E39 - 528iA - (2) - 2000 & (1) 1997
Also:
2015 Ram 3500 Dually, Cumins 6.7, Std.Cab. Long box 4x4 (To haul all this junk when necessary)
2014 Dodge Dart Rallye (Daily Driver)
2007 Mercedes Benz CL600 (Brabus SV12S)
Mercedes Benz SL's - (1) (2002) & (1) 1999 500 - (1) 1999 600
1967 Buick Riviera (2)
Thanks for that info. Here is what I know so far.
A. The code reader (Actron CP9215) confirms that the SAS readings are "Not Ready"
B. I then followed E39 Newbie's advice above (also detailed on this page at BavAuto.com) and confirmed that the air pump is in fact putting out lots of air during a cold start.
C. This led me to #4 on the BavAuto page, which reads:
D. When doing this, I would not say that there was a steady stream of exhaust gases coming out, but there was a definite fluttering sound and what felt more like slight variable suction than pressure. This did go away in a minute or so.With engine fully cold, remove the pressure hose from the check valve. As in step 1, start the engine and note if exhaust gas is coming from the valve (where the hose was removed), indicating that the valve is open. In this test, continue to run the engine. Does the valve close within a minute or so?
I don't have a Mighty Vac nor a vacuum gauge, so I suppose I should get my hands on them. I am tempted to take her on a spirited drive and see if all this goes away. Mom isn't exactly the leadfoot she used to be... ;-)
Otherwise it looks like a new O2 sensor is going to be needed.
You can do a "seat-of-the-pants" diagnostic just by disconnecting the secondary air pump hose. It connects to a stainless steel diaphragm valve at the front exhaust side of the engine. The hose comes from the air pump between the right headlight and right front tire. For about 90 seconds after a cold start the pump should blow loudly and strongly through the hose, and the exhaust gases should puff gently from the valve. The exhaust gases from an idling cold engine will be mild enough to feel using your bare hand. After the 90 seconds or so (70-120 seconds), the pump should shut off and the valve should close with no trace of puffs.
If that all checks out, the problem is very likely slow O2 sensors. Slow sensors raise no errors, not even with BMW-specific diagnostic tools. But the secondary air monitor will never be set to ready.
The $15-$20 replacement sensors on FleaBay work great for long enough to pass emissions this time, and maybe even next year. There might even be some that even last 100K miles, but under two years is my experience. They are cheap enough to treat as diagnostic replacements. But if you are paying someone else to do the work, or find DIY replacement annoying, you are better off buying Bosch branded parts from a reputable online distributor (not through FleaBay or Amazon).
I'm trying to remember when I bought some off ebay, I think they were labeled Bosch. But the car ran like crap, really, noticeably poor, though no CEL. Bought some off Amazon for ~$42(?) each and they've been fine for the past 70K. I don't understand it, O2 sensors are like spark plugs, wear items, albeit a long change out interval, but actually the same 100K now as plugs. But lots of people (far more on the Nissan boards for my Datsun) think they either last forever or at most only need changing out if there's a CEL lit. Not really a response to the OP, but just on O2 sensors in general.
98 328is
02 525ita
80 528i
81 528ia
and decades of owning and driving BMWs
Secondary are only runs on the first start of the day, that's it until the next day.
A MityVac is around $40 on Amazon. Well worth the price of admission.
You won't really feel a stream of exhaust from the valve. If you put vacuum on the nipple you'll hear a change in tone from valve open to valve closed. Also, you'll really want to determine how much vacuum is coming from the hose, just in case the valve isn't opening all the way.
Spirited driving won't set the SAS. It's strictly a cold-engine thing, and the sensor sets (or doesn't) in the first few seconds of the cold start. After that, it won't try again until the next cold start.
Current stable:
2002 525i (Daily Driver)
1994 SN95 Mustang 'Vert (The Bumblebee)
2001 325i Convertible (Beach cruiser project)
Thanks to everyone for the great info. I am researching O2 sensors and have found these:
Pre-cat: https://www.bimmerworld.com/Exhaust/...1-742-050.html
Post-cat: https://www.bimmerworld.com/Exhaust/...1-433-940.html
Is the post-cat one the likely culprit?
There is also this one from Pelican Parts that works for both applications:
Screen Shot 2019-06-23 at 7.14.26 PM.png
By the way, I couldn't find an easy way to get a direct link to the part without using the email icon and sending it to myself, so I took a screen shot... are you listening webmaster...?
Here is the link: https://www.pelicanparts.com/More_In...14&SVSVSI=0339
Last edited by LysanderSpooner; 06-23-2019 at 10:21 PM.
Just copy the URL, then paste it in the 5th icon from the right side.
Front and rear O2 shouldn't be the same part so don't beleive everything you read on the Internet.
The "upstream" or pre-cat sensor(s) is/are the likely culprits. IIRC, they are the ones that have the transient voltage drop when the SAS kicks in. If I understand it, the SAS exists only to lean out the exhaust gas in order to get the cat hotter faster. Strictly emissions hocus-pocus. The voltage drop just tells the computer that the air is blowing. That's the way it was explained to me.
The parts are not identical. The downstream sensors have longer wires on them. The physical sensor is probably the same.
Current stable:
2002 525i (Daily Driver)
1994 SN95 Mustang 'Vert (The Bumblebee)
2001 325i Convertible (Beach cruiser project)
The O2 are cold when the engine is first started, they don't start outputting a voltage until they get hot, somewhere around 600°F. The SAS pump provides air into the exhaust to help burn up the rich mixture in the exhaust which also heats up the O2's quicker. After the O2's start to send a signal to the DME the SAP shuts off.
Pre and post O2's also have different caps on the part covering the sensor tips.
Last edited by JimLev; 06-24-2019 at 09:03 AM.
The oxygen sensors are heated have been for years. Did you look at all the vacuum lines for the system especially the hoses at the rear of the intake ,manifold under neath
Secondary air is to heat the catalysts faster, not heat the O2 sensors.
There is no way that the same part will fit both upstream and downstream. Unless it's a "universal" sensor with crimps to reuse the old connector. Don't get those. The wires are teflon insulated stainless steel wire and you are unlikely to get a reliable connection.
The upstream oxygen sensors have short cables and are easy to change with a special oxygen sensor socket. I can swap the front one in about two minutes. The rear one takes a bit longer because my hand can't reach to guide it into place.
The downstream oxygen sensors have long cables, opposite gender connectors than the upstream sensors, and are a PITA to change. Changing them is best done .. by someone else. Or when the exhaust is removed. You'll need a crowsfoot style wrench and perhaps a wobble extension if you want to change them in place. Take pictures of how the cable is routed and clipped into place, because it needs to be put back exactly in the factory location if you want it to last.
Luckily the secondary air detection relies only on the easy-to-change upstream sensors.
Last edited by djb2; 06-24-2019 at 02:23 PM.
The pumped-in secondary air is cool, resulting in a lower exhaust temperature at the pre-cat sensors than without secondary air. It's actually cooling off the oxygen sensors, not helping to heat them up.
The point of secondary air, as well as moving the catalysts upstream into the manifolds, is to "light" the three-way catalyst as soon as possible with the goal of reducing cold start emissions.
Somewhat unrelated: Lighting off the catalyst as soon as possible during a cold start is a big deal for emissions. BMW was an early user of electrically heated catalysts, which have an electrical heating coil that produces a hot spot on the catalyst to help it light earlier during a cold start. It was used on high-end, low-volume models, apparently motivated by a desire to avoid tooling expense of mani-cats used in the high-volume models. It was a reliability failure, especially with the extended warranty required on emissions devices.
Yes it starts off as cool air but after it gets into the exhaust valve area in the heads it helps the rich fuel mixture (that is necessary for a cold engine) to burn in the manifold and pipe to provide heat to the O2's and then into the CAT to heat them up.
Lets just agree to disagree.
Last edited by JimLev; 06-24-2019 at 09:07 PM.
The vacuum hose that feeds the SAS is bright blue, quite pliable, and refuses to pull off by hand. Because it looks and feels like brand new, and because the SAS passes the test E39 Newbie mentioned in #6 above, I have quite a bit of confidence in it.
As for the ones under or behind the intake manifold, no I have not inspected them. I suppose I should. What are their functions, and what symptoms would their failure show?
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