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Old 11-17-2012, 09:52 AM
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540iman 540iman is offline
resident, old fart
Location: N.W. Indiana
Join Date: Sep 2008
Posts: 1,874
Mein Auto: 2002 540i sport
Quick synopsis as I have posted here before. It was minus 20 degrees at work. Car parked outside. Went to go home at day's end and SES was on. Read code and it was something to do with SAP-low flow, check pump, etc. Began trouble-shooting system. Pump was getting no voltage at start-up. Traced to 50 amp fuse under passenger seat. Fuse #107. Real PITA as passenger seat really needs to slide back into rear seat area. Did not disconnect battery so when I disconnected fine stainless steel wire connected to seat that tells air bag system exactly where seat is relative to front dash, I set an air bag system code I could not clear. Removed pass. seat, removed sill plate, pulled up 1" think insulation and basically 1/2 azz accessed fuse #107, it was blown. Power in, no power out with key on. fuse is a real oddball BMW special. Replaced fuse and re-installed seat. That's when I discovered I had created air bag error by removing wire and air bag system lost calibration of where seat was. Pulled SAP to see if I could see why it had failed. Drilled out rivets, opened pump and water flowed out of pump. Obviously froze that day and fuse blew as excess current was drawn trying to get pump to run with locked rotor. Cleaned pump as well as I could and it ran on bench with old battery, but I did not trust it. Water gets into pump only one way. SAP valve fails sticking open and condensation forms in pump. Water does NOT flow from exhaust to pump through valve. Hot air from exhaust flows "backwards" to pump when pump is not running to overcome exhaust pressure allowed to flow to pump by bad valve. Condensation eventually accumulates and pump fails. Before this day, I had had NO SAP error ever. Ordered new pump, valve, all tubing (from pump to valve), new relay (salmon-colored one in white box (ECU BOX) under passenger cabin air filter, fuse, new tubing leading vacuum to valve, etc. I replaced everythying. Started car, pump ran for about 90 seconds (normal) then shut dowen and I had SES error again. Read it and it was low air flow from SAP. Tried everything then took to BMW. BMW techs charged me nada, but said they could feel strong airflow from pump-just not enough getting to O2 sensors. They said my system was absolutely fine, but I likely had blockage in heads (carbon build-up). $8000 and they said whole system was a joke just to fire cats 60 seconds faster, but BMW needed in USA only to pass government emmissions-many cars do.

So, I had SES light I could never get to stay away. Found out in Europe and elsewhere, low air flow from SAP would NOT throw an SES, but just set a no problem code in ECU in other countries. No issue except places in USA requiring emmission test. They (BMW techs) said my old pump, before it gave up the ghost, may have just had marginally better air flow than new Pierburg which kept error at bay.

I was talking to Powerchips people about a Powerchip for performance-you could negotiate then and $1000 chip was negotiable to $350 or $400. P/C had an "option" you had to ask for which was the European SAP software for a USA car which as long as all the pieces were there in the car as prescribed (pump, valve, power to pump, etc.) the European software would allow a much smaller reaction of the O2 sensors to satisfy the ECU. The O2 sensors must see some lean condition when they expect SAP to be running so you can not just remove everything and go about your business-just less air flow was adequate. New chip cleared error from new pump. I just read recently about an Audi Pierburg pump that is nearly identical to E39 pump (uses same mounting ring, etc.) that is $107 NEW on Amazon. Guy found one at junk yard for $15 and it worked. Remember, always change valve with pump. At least clean it out as carbon builds up in it, diaphram rots, etc. Some can be brought back to life with good cleaning.

I am on 3 years now with chip and new BMW parts. Still HATE system, but it no longer will set an SES light unless system fails. If SAP runs for longer than about 3-4 minutes for any reason (bad relay-stuck closed) it will burn itself up. Pump is running far in excess of what it is designed to run full time. Should only run on cold starts for a minute or so.

BTW, chip made gas pedal feel more responsive, but I would have to bet it added absolutely no HP. Just changed how gas pedal signal was interpreted by ECU. No gas mileage change, but no speed limiter, RPM raised 500 RPM, and if you select DSP "off" it will start on the next ignition cycle still off rather than default back to dsp "on". People talk about sims to defeat SAP, but it was never a thought for me. I wanted a solution and wanted it NOW as if you get ANOTHER ses error, you will never know it if SES is always on. If that is all you care about you could just put black electrical tape over light and forget it. not an option for me. If I had it to do over, I would try Audi pump, and if still low flow, would call Powerchips and tell them you don't care if they do nothing else but give you the non-US software for SAP system and see how cheap you can get chip.

Last edited by 540iman; 11-17-2012 at 09:58 AM.
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