DIY: Troubleshooting S.A.S. and How to Replace the Famous Fuse # 107!
DIY: Troubleshooting S.A.S. and How to Replace the Famous Fuse # 107!
- I have emission codes P1421 and P1423 (S.A.S. codes saying not enough air is injected into the exhaust during cold start), which is very common for car this age 10y/100K miles.
- In order to understand the S.A.S. system, you need to read the attached pdf on S.A.S.:
---> In brief, when engine is cold, the Air Pump injects additional air into the exhaust to reduce pollutants.
---> The Air Pump is designed for high output but short run, so it injects air for anywhere between 2.5 seconds and 105 seconds or so, depending on engine temp.
- These are PNs for 1998 528i, listed only for reference, later years are slightly different. This is taken from www.realoem.com:
* Electrical Valve; PN 11747537612 (about $45)
* Air Valve: PN 11727540467 (about $110)
* Air Valve Gasket; PN 11727505259 (about $4)
* Pierburg Air Pump; PN 11721427911 (about $250)
* Air Pump Relay (K6304): schema is 85-86 and 30-87a-87, PN 12631742690 (about $8)
* Fuse #107: 50A Special Fuse: BMW PN 61138365901 ($4.00); Napa PN 782-1144 ($4.00). The BMW Fuse is covered in black and you cannot check it with your naked eyes (need Voltmeter or Ohmmeter to check). The Napa Fuse is see-through: within a glance you can see the fuse is good or not. I prefer the Napa Fuse. See pic:
- To be sure the Air Pump is bad, remove it and apply 12V to the 2 pins, if it does not run, either the bearing is seized or the motor is gone. You have 2 options:
1. New Pierburg Air Pump is about $250.
2. Rebuild the Air Pump using a standard bearing SKF 626 (ID = 6mm; OD = 19mm ; W = 6mm). Complete Air Pump Rebuild Info is here:
This is the sequence of S.A.S. system when you start the car cold:
- ECU sends signal to the Electrical Valve (this Valve sits under the Intake Manifold), which in turn opens a small channel to allow vacuum from the Intake Manifold to be applied to the Air Valve (which sits on the Exhaust Manifold)
- At the same time, signal is sent to the Relay to close the 85-86 "primary" circuit, which in turn closes the 30-87 "secondary circuit". In general, the "secondary circuit" in most Bosch relay circuits controls the high current flow.
- In the case of the S.A.S. Air Pump, the 30-87 circuit is controlled by the Fuse # 107, which itself is under the passenger's seat, thanks to the BMW engineers who designed this car with beer and bratwurst!!! In any other car, replacing this fuse is not hard because it is usually located under the hood. In the E39, Fuse 107 is a bit tricky to get too, but not too bad.
SOME DIAGNOSTIC PROCEDURES:
- Check the small Vacuum line leading to Air Valve, it is usually cracked with time/heat.
- To check Electrical Valve, during cold start, Disconnect (D/C) the small vacuum hose and feel for vacuum, there should be some vacuum from the small hose b/c the Electrical Valve opens the port to allow vacuum from the Intake to the small hose. Now re-connect the small hose.
- Air Valve and Gasket testing: Disconnect (D/C) the large hose to Air Valve, start engine during cold, after a few seconds there should be vacuum at the Air Valve (feel with your palm of your hand), if not either the Air Valve itself or the Electrical Valve is bad.
- Air Pump Testing: At the same time as above, the Air Pump is activated, so you should feel air blowing out of the large hose that you just disconnected above, if not, then the culprits are:
a. The Fuse #107 is blown. When this happens, usually something else is bad (like Bad Air Valve allowing water from exhaust to enter the Air Pump, destroying the bearing is blown ---> the Air Pump is dead. If the Air Pump is shorted electrically, the new fuse will be blown again. So if the fuse is blown, investigate it further. In my case the Air Pump was seized.
b. S.A.S. relay is bad (rare).
- Before getting to Fuse #107 under the passenger seat, check the S.A.S. Relay and its connector first!!! The Main Fuse Box is under the passenger side Cabin Filter. Remove the Passenger Cabin Filter Housing.
- Using Allen keys, open the Plastic Cover and you will see the setup below with all the main relays and some fuses here. To check the S.A.S. Relay, remove it & check for continuity between 30 and 87a, it should be 0 Ohm. Now apply 12V to 85 and 86, 30 and 87 (not 87a) is now connected.
- Now check the Relay Connector, take note of the relay pinout, then copy it to a piece of paper because when reading relay upside down, it is very very easy to get all the connector terminals mixed up! By copying the terminals numbers (basically mirror image of the relay) to a piece of paper, you eliminate error! Over the years, I have learned this the hard way, so trust me with this copying to a piece of paper. There should be 12V to #30 terminal all the time. See pic:
PROCEDURE TO REPLACE FUSE #107 UNDER PASSENGER SEAT:
Now that you have determined that there is no power to terminal #30 in the Relay Connector itself, time to check and replace the 50A Special Fuse.
1. The Trim piece: using flat screw driver pry it up, it is held by 3 White clips.
2. The Seat is held by four (4) Torx #50 bolts, remove them but no need to take the seat out of the car.
3. The Vertical Trim piece: undo the bottom part only to allow the carpet to be folded back.
4. Note how the carpet fits (the front carpet piece slides under the rear piece).
5. Fold the carpet back and place a brick on it to hold it there to free your hand. You will see a Styrofoam insulation piece. In order to remove the Styrofoam in its entirety, you have to remove the plastic tunnel (HVAC Tunnel), which is more work! I bypassed this step: I leave the plastic tunnel alone but break the styrofoam at where it meets the plastic tunnel b/c it is a only a piece of insulation, nothing fancy about it.
- Use a short piece of wood to prop the seat up about 12".
6. Now you see the Electrical Distribution Center, remove the white plastic covers to expose the Red (+) connections. Ground (Brown Cables) is just to the Left of this distribution box.
7. Fuse Block has a total of 8 fuses. Fuse #107 is on the far Left. See picture:
8. To test the Fuse, use a Voltmeter (not Ohmmeter for now).
9. Note the Large Red Feed Cable side, it feeds power to the electrical block where it branches out. So probing on that side must read 12V or so. Now probe the other side of the fuse, it should read 12V as well, if it reads 0 volts, the fuse is bad.
10. To replace the 50A Fuse, it is held by 8-mm nuts and square washer. Use a small hook to hook it out. Remove the fuse and confirm that it is bad with an Ohmmeter: when a fuse is bad it reads infinity Ohms (open circuit).
* CAUTION: this circuit is always "hot" with 12V, even with key out of ignition! If you are not comfortable working with "hot" wire, then disconnect the red cable from the trunk battery. I did this whole thing with the battery connected, just pay attention not to touch any ground while removing the 8-mm and 10-mm nuts.
11. The medium-sized red cable feeding separate electrical items in the car is held by a single 10-mm nut.
12. NOTE the torque for these nuts, basically tight and snug a bit:
* 8-mm nut: 8 Nm
* 10-mm nut: 15 Nm
13. Now you need to address the Air Pump. Either buy a new Air Pump or rebuild it, otherwise this fuse will blow again! Info for Air Pump is mentioned above.
That is all boys and girls, not too difficult if you know what you are doing!
Great work as always CN90---hope I never have to --but knowing the info is there will make it more bearable
if I have too make this repair.
Another cn90 DIY bookmarked! :thumbup: This DIY is a great complement to the simple replacement of the air pump and valve. If your fuse is the culprit, this DIY will save you big $$$ over replacing the air pump. My previous e39 spit out air pumps annually. This one has been solid since I got it :dunno: Very strange...
You guys will be pleasantly surprised.
So I ordered a brand new pump which will not arrive until next week. In the mean time, I reset the CEL light, removed the Air Pump from the car and guess what, for the last few days....no codes at all!
This is because when the Air Valve (which sits on top of the exhaust manifold) is activated during cold start, it acts like a vacuum valve sucking in air. The Air Pump helps push more air in.
When an Air Pump fails, it acts like a road block to air flow because it stops running.
However, removing the Air Pump allows the Air Valve to suck in air as it wishes, which accomplishes the same job of reducing pollutants. It will be a bit noisy during the cold start, then it will quiet down.
So, if you are so tight with budget for a new Air Pump:
1. Remove the Air Pump
2. Reset the OBD-II Check Engine Light.
3. Cap the open end of the hose with home window screen (the same stuff sold at hardware store to repair broken home window screen, which is the screen to keep bugs from getting inside the house). It is a few dollars at hardware store. Then duct tape and gently zip tie it. This is to prevent leaves/debris from getting into the hose.
Try this and report back.
I was pleasantly surprised when I discovered this "Eureka" while waiting for the new Air Pump to arrive. "Look Ma, no code"....:)
Anyway I already ordered a new Air Pump, so the Air Pump will go in.
The SAS system sounds great in theory but what a piece of junk (to make tree hugger happy for 1 minute!).
:rofl: Nice DIY!
CONGRATULATIONS. (this will help get rid of unsprung weight :bigpimp:)
Thanks for picking up the error!
And YES Day #5 running w/o Air Pump and no CEL codes!
9 times out of 10 a failed pump is due to a failed valve at the exhaust manifold.
problem is that when the valve fails it does not "suck in air" it lets exhaust gases out. Listen for your new exhaust leak when the engine is cold, and look at the soot that will develop wherever your open hose ends as signs. Why do you suppose an air pump is needed? if it drew in air by itself they would have designed it that way. All you are doing is blowing exhaust under the hood on cold start, which is not good to recommend considering your cabin filters are also in that area. If they are perfectly sealed you may not notice, but an aging e39s cabin filter system is usually anything but air tight. Sorry but I can't agree with that even as a temp fix. Carbon monoxide is lethal. This temp fix relies solely on you having a good valve at the exhaust, which is not the case more often than not. If the one way valve is working you may get away with it.
The other thing to mention here is that if your car is eating these pumps annually or more change the valve! They get full of carbon and fail, which ruins it and lets exhaust out into your pump, or if you have unplugged your pump it will just waft under the hood and car. One of my 528i cars has had 3 of these pumps fail in the past. The other is on the OEM pump from 1998. Guess which one has a good exhaust valve in it?
Your diagnosis and other info is spot on and will be very useful for others, but I think the best bet if you need a new pump and valve is to leave the old parts alone until you have replacements. I'd rather see a CEL for a couple days until parts come in than risk breathing in poisonous gases.
Excellent write up. Very insightful. I'm going to some time to go thru all the read materials. Great stuff. It's not a common failure, but most electrical issues is a pain.
I am not advocating throwing away the Air Pump. I am simply reporting what I observe b/c I find it interesting.
Actually my Air Valve is brand new. I understand that a Bad air valve allows exhaust air/moisture to enter the Air Pump and destroy the Air Pump. But in a normal Air Valve, it sucks in air during cold start (disconnect the hose at the air valve; run the engine during cold start, try it with the palm of your hand and you will see it sucks in air; then re-connect the hose).
For a long time, I always thought the Air Valve simply opens a gate, then the Air Pump blows air into the exhaust manifold, then the O2 sensors registers a change in reading, and the ECU is happy about the readings, no codes are reported.
Well, I checked and during cold start, the Air Valve sucked in air!
* My observation:
1. During cold start, it has similar noise like as if the Air Pump is running in a normal car; nothing unusual.
2. Then roughly 1 minute later, all quiet like the way it has been the last 4 years. Checked the hose: no vacuum b/c the Air Valve is shut now.
Re: carbon monoxide etc.
My disconnect point is not under the hood, it is in the wheel well, where the blue arrows area, just behind the fog light area. So in the event the Air Valve fails (if you remove the Air Pump), exhaust gas will enter the wheel well area as shown; and in that case of Air Valve failure (the Air Valve lasts about 80-100K), it will be noisy, and you will know about it and change to a new Air Valve. No C.O. danger to worry about.
If my theory proves to be correct, then one can always add a short hose to route it under the bumper, just in the event of Air Valve failure, exhaust gas is pumped under the bumper. I think this whole SAS thingy is over-engineered.
trust me, I am not fond of the system myself, having went through a couple pumps before I realized that valve was shot years back. I have run my personal car without one for some time, I keep wanting to fix it but other things take priority. Even with a work discount the parts are $.
One interesting tidbit I will share from my experiences with my car, 98 528i. Recently reprogrammed the entire car's modules after a manual transmission swap so that the various error lights would not be on anymore and I could pass smog. I do not have the air pump plugged in electrically at the moment, nor was it when I programmed the car. I was expecting the same old SAP codes to register a day or two after flashing the DME, but it never came back. I have put hundreds of miles on it since and still no light. I wonder if by leaving it unplugged when I reprogrammed the car's modules if it may have caused the car to no longer look for the thing. My other thought is that the software I used on my engine computer may have been an updated version that does not trip the light for SAP errors. (flashed DME with progman 32) Either way a trouble code scan of the DME shows "no errors!" Works for me. :)
Hello Mark. What did you use? Carsoft or GT1? Or something else?
cn90, how did you post pictures like that on this forum, where pictures are shown in full size without clicking on the attached pictures?
2. Move mouse over to the pic and Right click Properties.
You will see it says for example:
(In new post with new pics, it usually says
but all you need is the attachmentid #, so delete the blahblahblah after the attachmentid number).
3. Then Click on "Insert Image" and enter the link wherever you want it.
Could you review and edit your most excellent post? I believe there is a typo in the WDS Wiring Diagram System print you have displayed. The Secondary air pump relay in the diagram has the #30 terminal and the #87 terminal reversed. I just triple checked this on a '01 525i and the #87 is always hot and the #30 has continuity to the pump.
This means your drawing of the K6304 Connector for the air pump relay will also need editing. We wouldn't want a noob to think that his BMW has crossed it's Plasma streams somewhere and undergone Total Protonic Reversal. :eeps:
I made the same mistake because I was looking at the RELAY instead of the CONNECTOR.
It can be confusing if you are not careful!
You need to get the CONNECTOR pins properly labeled!!!
Best is to get a piece of paper and place the RELAY on top on the paper and trace the numbering system like 30, 85, 86, and 87, now use this piece of paper for the CONNECTOR numbering system.
It is easy to get the 30 and 85 terminal mentally reversed but not the 87 and 86. The labeling on the diagram you made of the CONNECTOR for the relay is correct but the image of the WDS Wiring Diagram System does not conform to the testing I did.
When testing this '01 525i I have in the shop I find that the 87 slot on the CONNECTOR is definitely hot all the time while the 30 slot definitely shows continuity to the plug for the pump. (testing also shows that 86 becomes hot as it should when I turn the ignition on)
The image (and your description) of the WDS Wiring Diagram System suggests that the 30 slot in the CONNECTOR should be hot all the time and the 87 should lead to the pump. This does not conform to my probe testing
One of the reasons I had to be extra careful about this is that the physical layout of the vast majority of relays I have seen in my 20 years as a mechanic specializing in electrical trouble shooting (my major in collage was Electrical Engineering) has the 30 and 86 terminals reversed from your drawing. Typically 85 and 86 are the low current actuating coil terminals and they stand opposite and parallel each other on the relay while 30 and 87/87a are the high current load bearing pair of terminals that are opposite and perpendicular to each other on the relay. This Air Pump relay changes that conventional configuration to the layout you have correctly described in your drawing of the CONNECTOR.
The image of the WDS Wiring Diagram System is technically set up correctly. 30 SHOULD be hot all the time as per German wiring convention and the motor terminal 87 is properly switched between hot 30 and ground 87a to dump the back EMF and park the motor. Unfortunately that does not conform to how the car is actually built and the screwball (in my experience) layout of this Air Pump relay and its connector.
*IMPORTANT NOTE* Please read the reply I made right after this post.
Now that I think about this you are right in your descriptions and diagrams. I believe this 525i was wired incorrectly from the factory so I am going to swap the wires going into the 30 and 87 slots in the CONNECTOR. 30 SHOULD be the hot wire while 87 SHOULD be the pump wire.
The car being wired improperly as it has been would work OK but it would not give the back EMF in the motor anywhere to go when switched off which would be hard on the motor and hard on the relay. It would also confuse the poop out of anyone who is trying to probe and diagnose this wiring. :confused:
What are the car's symptoms?
I find it hard to believe the car is wried wrong from factory.
Make sure you look at 87 and 87a carefully!
Never try to replace fuse #107 with the battery still connected unless you like resetting air bag faults.
The Pierburg for an Audi A4 was just bought used at a salvage yard for $17 and mounts in the same mount as ours. A new air pump for the A4 can be bought for $100 on Amazon. Why buy the BMW pump?
Disconnecting the SAP will not act like a SIM-Sorry. Been there, done all this......
Good news and good work CN90, but nothing new here.
Is my problem in the relay?
First of all, let me thank the editor of the DYI for an outstanding job. It has helped me a lot when I replaced the secondary air pump on my 2000 528i.
That being said, it is still not working. Here is what I have done.
1- The BWM dealer told me my pump was dead and needed to be replaced. So I replaced it with a new one. I also replace the air valve, and hose and the hose.
2- Since doing this did not help, I replaced fuse #107 and tested it. The new one works fine. It gets 12v and there is continuity through it.
3- Since my air pump was still not working, I had a look at the relay and measured voltage and resistance. Here are my findings:
- 87 was hot (12v) all the time
- 30 is not hot.
- 85 only had .1v with the key in position II
- resistance b/w 85-86 was 78 ohms (not sure if this is important).
So, if I understood your post correctly, there is something wrong with the connector. Or maybe it's before the connector.
Can anyone help?
Your #86 terminal on the connector should be hot (12v) when you turn the key on. If not, then you need to check the F31 fuse (where is that located?).
You can test the air pump by putting a jumper wire between 87 and 30 to see if the pump runs.
You have the same 87-hot (from fuse 107) and 30-cold (to pump) apparent backwards connector wiring that I believe I have on this '01 525i. My customer has the car right now. Give me a week and I will get the car back to install a good pump I got at a wreaking yard for $125 (his original pump was all melted down inside and not rebuild-able). I will triple check everything, swap the wires so #30 in the connector is hot and #87 in the connector runs to the pump then report back on how it all turned out.
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