Member
I have a 2002 530i with about 114k miles. Recently the check engine light went on, and the codes were the two Secondary Air System Bank 1 and Bank 2 codes (po491 and po492, if I recall correctly). The strange thing is that my air pump seems to work just fine (it cuts on, blows very strongly, and doesn't make any strange noises). The valve also seems to work fine (it does open and close when you apply vacuum). So I then wondered if the valve wasn't getting vacuum to it. So I followed the vacuum hose back to the back of the motor, and found a section of hose that was dry rotted. I replaced that. So far, the CEL has not come back on yet, and there are no codes (but I've only started it once or twice since replacing the hose, and I figure it's going to take a couple more starts before I'm confident that CEL isn't coming back on).
Would a vacuum problem cause these codes (i.e. if it won't open the valve)? The hose that goes to the valve connects behind the engine (by the firewall) to an electric valve, part number 11747537612. Could this electric valve be the problem? It's part number 5 on the following realoem parts diagram:
http://www.realoem.com/bmw/showparts...03&hg=11&fg=45
I'm just wondering how something "mechanical" like the check valve could cause this code. However, the electric valve on the diagram seems like it would have some connection to the ECU. Of course, if my CEL doesn't go back on soon, I'll know that the vacuum hose solved the problem.
If this is the cure to my problem, it sure beats buying a $375 pump and a $100 valve.
resident, old fart
If the valve does not open, then how is the air pressure from the SAP to get to the exhaust system? Maybe you are thinking the check valve works the wrong way. The check valve is there to keep exhaust gases from flowing toward the pump. So, if the valve does not open for whatever reason...rotted lines, bad valve, etc. then the fresh air can not get into the exhaust ahead of the O2 sensor (pre-cat) and make the O2 sensor go lean as the ECU expects when the pump and the valve are functioning correctly. This is basically how the ecu interprets a properly functioning SAP system. It looks for the pre-cat O2 sensor to see lean conditions all the while the pump is running.
Member
Yes, I realize the valve opens to let the pumps push air into the exhaust. But I wasn't aware that the 02 sensors would throw the po491 and 492 codes if they didn't detect the increased airflow from the pump during cold starts. I read somewhere that the computer detected the electrical draw from the pump, and the lack of the draw caused the code. But what you say makes sense. Hopefully replacing this 4" section of hose solves my problem!
Thanks!
Member
Many have tried to create a SAP system sim to eliminate this somewhat useless, poorly designed SAP system and avoid getting the codes. I believe that they have all been unsuccessful. I believe that the fault code can be triggered by either "fault": insufficient voltage draw which indicates a malfunctioning pump or an incorrect exhaust mix by the pre-cat O2 sensor (caused by a defective valve). You have correctly diagnosed your problem and have applied the proper corrective action. Well done!
Prodigal Member
I'm waiting for a group buy on SAP's..
UNDER CONSTRUCTION
- 2000 528i Sport -
Got any questions about my car? Feel free to PM me!
Member
I hope this isn't true - I just paid AA $199 for a SAP simulator that damned well better work and keep the CEL from coming back on!Originally Posted by fudman
Member
This morning when I drove to work, the CEL came back on. So I went to the auto parts store and bought 3 feet of vacuum hose with the intention of finding and replacing all of them. I followed the vacuum hose from the check valve all the way back to the back of the engine and to the electric solenoid valve (I had already replaced both hoses to the valve). There was another hose coming off the electric solenoid valve to the underside of the intake manifold. Not only was that hose dry rotted, but it was also completely collapsed. So, of course, I replaced that as well. I've erased the codes, and hopefully this will take care of the problem. In any case, I know I had some kind of vacuum problem with the collapsed hose, and I'm hopeful that this fixed the problem.
Last edited by lps; 09-04-2009 at 07:04 PM.
Member
Nice job finding the collapes hose. I think you've got it.
Hey GreenAdam,
Where do you buy the SAP SIM? I'm sure there will be a few interests on here want to do the same somedays including me. Thanks man.
Last edited by 16valex; 09-04-2009 at 07:16 PM. Reason: Automerged Doublepost
Member
Thanks! I'm right proud of (hopefully) finding a $2.00 solution to a $450 problem.
I'd be interested in hearing how the SAP SIM works, as well. If my $2.00 of vacuum hose don't fix my problem, I'd rather spend $200 on a useless piece of electronic hardware that keeps the check engine light off than spending $450 on useless pieces of electronic hardware that do some useless things, plus also keep the check engine light off.
Member
Do a little search on "S.A.S.".
Basically during cold start, extra air is injected into the exhaust, reducing emission.
This is accomplised by the Air Valve opening to allow air to be injected.
If the Air Valve fails in open position, water from the exhaust back-flows into the Air Pump, killing it. The Air Pump will be drowned in water!
I have a 1998 Volvo V70 as well this 98 BMW 528i. Every 90K miles, I change the Air Valve and the vacuum hoses. Air Valve lasts about 90-120K or so and that is it.
Use BMW or Pierburg (Pierburg is OEM) Air Valve only = $90. Change the Air Valve gasket too.
If you replace the Air Valve every 80-90K and its hoses preventively, the Air Pump ($280) will last the life of the car.
Member
Just wanted to give an update. It seems that the vacuum hose was in fact the cause of the check engine light. My son also has an '02 530i, and I decided to change all the hoses on that one, too. It has far fewer miles on it than mine, but the hoses were pretty dry rotted (but none of them had collapsed).
ShutUpWomanGetOnMyHorse
Would you happen to have the part number for the air valve?
How long did the job take and did you follow a D.I.Y here?
Part #?
Member
Valve - #11-72-7-54-0468
Hose - #11-65-7-80-3732
No DIY needed. Probably took 15 minutes. See http://www.realoem.com/bmw/showparts...03&hg=11&fg=45 for the layout.
Last edited by fudman; 10-04-2009 at 06:02 PM.
BMWCCA 484984
cnn just posted this DIY.
1998 528i S.A.S. Pierburg Air Pump Maintenance and Rebuild Info
Member
Where is the secondary air pump on a e-39 540i?
pompous a*s
About 30-40 degrees around the passenger side wheel well (0* being @ the front of the car, 180* being @ the back of the fender), just above the fender liner.
resident, old fart
Your assumptions on how the SAP works are incorrect. It is not the current draw from the pump that satisfies the ECU that the pump is working. It is the actual swing in the output values from the O2 sensors that satisfy the ECU. This is why Carbon build-up can cause such heartache. The fresh air MUST reach the O2 sensors and the O2 sensors must go lean in concert with the pump being on. Surprised no one chimed in yet and told you. sorry
BMWCCA 484984
musicman,
Welcome to Bimmerforums.
It usually helps when a question like this is accompanied by the Model Year (MY) information of your car, preferably the production year.
Unless I am mistaken, the answer to your question depends on the Engine Management System your E39 model has.
540i, M62s with either the Bosch M5.2 (up to 9/1997) or the Bosch M5.2.1 (9/1997 to 9/1998) DME do not have a secondary air injection system or a Secondary Air Pump (SAP). The four other DMEs (Siemens MS 41.1, 42.0, 43.0; Bosch ME 7.2) have secondary air injection systems and use SAPs, and as far as I can tell, the positioning of the pump is the same for all of them.
(Photo courtesy cnn)
Source: Bentley BMW 5 Series Service Manual; 130-1,2 "Fuel Injection".
Last edited by jamesdc4; 10-12-2009 at 11:58 PM.
Member
How about on a 2001 M5? I see nothing that resembles this equipment in my engine compartment.
Also, I am only getting the error on Bank 1 (P0491). Is bank 1 the passenger side? When I start the car, I hear what sounds like a little bit of excessive noise coming from that side. It goes away in a couple of minutes. I am hoping its a bad hose.
Member
According to the Hayne's manual the SAP system injects air into the exhaust system only on cold days. The air mixes with the exhaust gasses and ignites to cause afterburning
meant to quickly heat up the catalytic converter so that it cleans the exhaust right away instead of waiting for it to heat up.
Member
Sounds like Haynes is confused. The SAP injects air when the engine is cold. Outside temperature, provided it is below about 150F, is irrelevant.
d-
BMWCCA 484984
That's a good question. All the info I posted above obviously doesn't include the M5s.
You may want to ask that question on one of the M5 dedicated forums, but in the meantime, you could partially pull your passenger side wheel well cover and take a peek.
Member
I plan to do just that as soon as it quits raining (we're on day 3).
I think I found the valve yesterday when I was changing the thermostat.
Prodigal Member
Man i feel ya.. it took me 7 days just to change my cam sensors with the way this weather has been..
UNDER CONSTRUCTION
- 2000 528i Sport -
Got any questions about my car? Feel free to PM me!
Member
Thank you BMW- I just spent over $400 at Bavarian Auto to swap my SAS pump and the valve while I was in there so that I could pass NY inspection.
The 10mm nuts are a PITA to access on the 03 540.
And here's the best part- there was nothing wrong with either!!! The vacuum line had broken off the valve. I went ahead anyway and swapped the parts b/c the car has 100k and what the hell.
One of the few times I didn't diagnose and just mouse clicked the parts to my door. And bam.
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