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DIY: Troubleshooting S.A.S. and How to Replace the Famous Fuse # 107!

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#1 · (Edited)
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:
http://www.bimmerfest.com/forums/showthread.php?t=402816

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!
 

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#76 ·
Wow, what a gold mine to go through. Thanks cn90. I'm on the trail of code P 0492, SAS bank 2.

Hoping its valve and maybe small hoses going in. I should be able to tell on cold start up whether the pump is still working, correct?
 
#77 ·
Since you don't have both banks failing, suggests carbon build up in one head, bad O2 sensor (1) on bank 2 side, possibly it is a very small but plausible to DME low flow rate just to one side due to a loss of total air volume which could include valve, plumbing, and or weak pump. However, if I look at error code literally, it appears to be not enough air flow making it through just one head which could be CBU issue or piping from valve to heads leaking or just one oxygen sensor which is greedy and wants even more exhaust dilution. Would be interesting to know if it were possible to send the output of bank one O2 sensor only to both inputs of O2 sensors at DME. Could cause drivability issues worse than stupid SES light due to emission issue. There are software solution from PowerChips, but expensive. You might try swapping O2 sensors first from side to side and see if error follows O2 sensor or stays with bank #2.
 
#78 ·
Thanks for thoughts. The O2 sensors are pretty new, pre cats changed 1.5 years ago. If sensor was bad that would be a different code wouldn't it?

Tried to listen this AM closely to cold start, couldn't really tell if pump was working.

Doru, how difficult was access to the valve?
 
#79 ·
SAP system sends injected air from the pump, through the valve, air into both heads (on a 540). O2 must see an appropriate swing to a leaner condition when pump is running. I did not mean to suggest that the bank that is not working has a bad 02 sensor, but if the pump were not running at all, you usually get an error on both banks. Swapping O2 from side to other side would just rule out sensor that does not need to be bad as in "not functioning", but may just not send a signal to the DME that it is seeing a proper lean swing while pump is running.
 
#80 ·
Hey all. Reread this thread again, but I'm a Noob when it comes to electrical.

What I'm searching for is a clear, "talking to a 6 year old" type description of how to confirm the problem is NOT electrical, prior to replacing the secondary air check valve. And if possible, confirmation the valve can be reached via the pass wheel well, with car on lift.

This thread is a godsend -- the threads on M5Forum all go down the winding road of carbon buildup, not helpful.

Thanks in advance.
 
#81 ·
EXACTLY what error are you getting? Do you have a multi-meter? The car in question is the M5, correct? Do you want to walk your way through it and I will take you under my wing such that you understand 100% how the sap works and maybe a little bit about electronics. If the answer to all these questions is "yes", then go to one of the big box hardware stores and tell the people in the electrical department that you want a digital multi-meter capable of reading up to 10 amps. If you are in luck, you should find one for under $30. You don't sweat it as you will likely have two and your second one can be a "Fluke" brand bought on Ebay. You will use it a thousand times over the course of your lifetime. Might as well get handy-now.
 
#82 ·
Thanks.

I'm on the trail of code P 0492, SAS bank 2.
I have a multimeter, never cracked the plastic.
 
#83 · (Edited)
Just for kicks (I'm an electronics tech) I removed relay completely on my 2002 and 2000 540s. As anyone can see, the wire from fuse #107 is solid red-not red with black or yellow or anything but SOLID RED. It leads from fuse #107 to terminal 30 on the socket and terminal 30 on the relay, btw. Terminal #30 has a large red wire leading to it and has 12VDC with lots of current handling capacity. Cn90s schematic and my car are exactly alike. Terminal 30 of the relay is not the center of the SPDT relay, but nonetheless has 12 VDC at ALL times. Terminal 87 is the lead to the pump and when 12 volts is applied to the relay coil through terminals 85 and 86, the relay energizes which puts terminal 87 to terminal 30 and energizes the pump. When the DME says "enough" the coil drops out and terminal 87a is the NC contact and grounds the pump. Terminal 87 in the NO contact and gets 12 volts from terminal 30 which is always hot because it is fed from fuse 107. My relay and my relay base and the schematic CN posted all agree on my cars. Do not run a jumper between terminal 30 and terminal 87 as you will blow fuse #107 as the pump power lead is grounded because it is still connected to ground through pin 87a. If you want to force the pump to run, take the connector off the pump. then ground the appropriate terminal of pump and run a lead from pin 30 to the pump. My cars agree entirely in all respects to the relay, the relay base, and the schematic. I would let car sit in garage overnight and then have multimeter connected to pump connector and see if pump is getting 12 volts. I would then go from there.

I have had to replace 2 saps, valves, hoses, fuse and relay and one car took PowerChips software to over-ride CBU issue in M5 heads.
 
#91 ·
Now, go to your local junkyard and get some odds/ends.

Ebay is another good source.
Some people part their E39 and sell the whole package (fuses, relays) on ebay for cheap.

I pulled a whole of stuff from an E39 from my local junkyard:
- bulbs
- relays
- fuses

This way in a pinch, I can fix things instantly w/o going to dealer for mundane stuff like relays.
 
#92 ·
Will do ill stock up on some misc things.

Ran I jumped the relay yesterday pump kicked on, replaced the relay and it wont turn on. Could jumping the fuse mess anything up. I checked the fuse and its good. I plugged the relay in without disconnecting the battery.
 
#101 ·
I think you are on to something! Do you think its possible that when I jumped the relay to test the pump it could have fried the pump or something else? When I jumped the relay it sparked and the pump kicked on. I lost connection so I did it again to make sure I heard the pump and the wire smoked a bit so i pulled it off. I breezed through the delete thread but I'd have to really read it to see if im capable lol
 
#106 ·
Secondary air pump problem solved

I read this forum over completely and HAD a problem getting the SAP to work. I tried everything mentioned with countless hours tracking down the problem. I took everything apart and did every test procedure. Long story short after replacing every possible part it was corrosion that destroyed the brown wire crimp inside the connector on the pump itself. I cut the connector off and used some new bullet connectors crimped onto the wires feeding the pump and all of my problems were solved. I HOPE THIS SAVES SOMEONE THE MANY HOURS I SPENT WITH THIS PROBLEM. My sincerest thanks to all of those who posted in this thread to help me finally solve this problem!
 
#107 ·
I just threw out my SAS. While taking out the pump, my connector was completly shorted out. The insulation around the pump wires going into the pump was crumbling off. Proobably due to heat from shorting.

But yes, this issue may be pretty common with pump failures. Something to look for.
 
#109 ·
Update on Pierburg Air Pump after 5y/50K...

- I know the electric motor is made by Johnson Control and it is made in China.
- After some 5y/50K, the air pump is very noisy, especially in the morning.
- The car is 17y/150K old.
- Disclaimer: I love the environment and don't want to produce more emission than necessary but this air pump SAS thingy drives me nuts.
- In the absence of diode mod like the Volvo people do to fool the ECU, I'd have to decommission the SAS system b/c I don't want to spend another $260 on this useless system.
- I don't have appetite to rebuild the bearings inside the air pump.
- Newer models (Volvo, BMW) use timing to reduce emission, so this SAS system is a design that is obsolete.

So:
1. Small piece of black electrical tape to cover the CEL light. Once a month, I scan for error codes that are not SAS related.
2. D/C the larger hose that feeds the air valve to prevent further damage to the air pump.
3. D/C the small vacuum hose and plug it with a small screw (you don't want the air valve to be activated pushing exhaust gas into the ABS module that sits nearby.
4. Find a rubber plug and plug the air valve larger opening (the opening that goes to air pump).

Car is now quiet in the morning.
So for those tree huggers, I am sorry but I am happy.
 
#110 ·
I've had the CEL with codes P1421 and P1423 on for the better part of the year. I bought a new Pierberg pump, diverter valve/gasket, plastic valves and solenoid, and vacuum hoses thinking it would be a quick replacement with CEL gone forever - until I read this thread all the way through - OMG. Now the big question is whether a warmer month than January would be a better time to start this journey. Hopefully not a 5 year journey. I don't have the patience or electrical expertise that cn90 possesses.
 
#113 ·
If you have state inspection (does Michigan have state inspection for vehicles?), then you need this SAS system.
Another approach is to clear the codes before the inspection should you decide to bypass this SAS thingy.

If you don't, then do what I just did, de-commission the SAS system and sell what you just bought on ebay, or sell it to someone else in this forum.
 
#112 · (Edited)
Troubleshooting S.A.S. and How to replace Famouse fuse # 107

540iman The low air pressure alarm means that your Pierburg pump in getting 12VDC, but is just not putting-out sufficient volume of error. Seems you can hear the pump as well. This air generally means your pump is weak, you have an obstruction in the head passages filled with carbon, or the valve is not opening sufficiently. Just FYI, I replaced the fuse (mine WAS blown due to the SAP rotor being locked by ice, I replaced the salmon-colored relay. I replaced the pump with $600 genuine OEM, I replaced the valve with OEM, along with all hoses from the pump as well as all the vacuum hoses that trigger the valve. In a nutshell, I replaced everything and I still got a low air pressure alarm. I then replaced the pre-cat O2 sensor just for "luck". Nothing changed.

I took the car to the dealer for just a scan of the SAP system and what was revealed to me was that the air flow to the exhaust system was weak. The swing of the O2 sensors was too weak to satisfy the OEM. I was told I had the dreaded CBU within the heads themselves and only a gun=drill would fix that at a cost of $8000. I bought the powerchips software which opened-up the parameters for which the O2 swing-although minimal- was, in fact, present. Power chips had a software flash which wad the European software which did not require as much air flow to satisfy the ECM. It worked as long as the caveat that the entire SAP system must be in tact, functioning to so degree, but the acceptable air flow was significantly less to satisfy the ECU. This system re-flash is NOT a simulator mimicking the pump, but simply allows a weaker air flow to satisfy the ecu. The entire system must remain intact and
functioning at some reduced level. It is NOT a SAP delete.

My minimal air flow was sufficient to satisfy the oem and saved me $8000 for a gun drill. I would save checking fuse 107 unless I found no voltage at the salmon-colored relay. Many on the M5 forum use this work-around as M5s are quite a bit more affected by clogging of the Sap flow. You will pass emissions if low air flow is your demon.

This may only cure a small instance of the code, but it does work if blockage is your fate. You then have inexpensive "cures" such as the amazon Pierburg pump. you may clean the valve with engine cleaner. such as seafoam, etc. Euro cars need some airflow, they just need less. G/L

My mileage has not decreased at all and in fact, increased!

P.S. 3rd year on same pump and all parts in SAP system still going strong.
Yesterday 05:36 PM
 
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