bmw7833
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Exploring the (2000) 528 OBC----------------------------From: Lon LeaderJust for reference here - if you have a 540 or, I believe,a 528 with NAV, with the 'high' or 8 function computer youcan learn about it at Peter Glaskowsky's web site:http://www.ideaphile.com/bmw/540-obc.htmlIt makes interesting reading because the displays appearwith short text discriptions that are not available with the 'low' OBC. Please note however that while there aresimularities between the two computers there are alsosignificant differences in some of the displays.Back to the 528 ('low' or 4-function) computer. There are 21 'tests' or 'displays' in total, and some of them have sub-displays. Tests 1 (car data) and 2 (instrument test)are accessable without 'unlocking' the OBC. There is NO chance you will screw anything up (except MAYBE reset the trip meter) if you don't 'unlock' the computer (which requires you to do something specific). Even with the computer unlocked there are only two tests (20 and 21) that allow you to change anything and those will be explained later. (One of them, 20, is the fuel correction factor that I suppose is the reason you're reading this.)Access is a little more complicated on the 'low' OBC becausethere is only one control that you use - the trip resetbutton on the dash. There are only three things you can do with one button - a 'short press' (less than 1 second), a 'longer press' (greater than 1 second), and a 'don't press'(ie: wait a second or two without pressing the button). OK, with the key in the accessory position (no need to have the car running) to get started you press and hold the trip button for several (more than 5) seconds. As you first press the button in, the trip meter will appear to reset to zero - don't worry, if you keep the button pressed untilyou're into test mode when you exit test mode the trip meter will be restored to what it was.After 5 seconds or so, the mileage/trip display will change to:_teSt_ __1._VERY QUICKLY release the button (if you continue to hold the button, it will pop you back out of test mode)One thing to note here is the word 'teSt'. When that is on the display you are in what I call 'index' mode - it is at this point you can step from one test to another. What happens next depends on whether you quickly press the button again ('short press') or do nothing ('don't press').If you quickly press the button again the word 'teSt' will remain and the __1._ will change to __2._, and if you repeatedly 'short press' again and again, it will step up through the index of tests to _teSt_ _21._ and then start over again at __1._. These are the 21 available test displays and only __1._ and __2._ (and _19._) are availableto access without 'unlocking' the computer. (_19._ is the 'unlock' panel). OK, back at _teSt_ __1._ - if you pause there ('don't press' the button for a second or two) you will 'drop into' (or access) test 1's first display (it has 8 sub-displays).You should see something like:_xxxxx __1.0 (the first digits, censored here, will be your VIN number)If you then 'short press' the button repeatedly you will step through all the 8 displays of test 1 (car info) - here are what mine say:_xxxxx __1.0 (VIN number) __4812 __1.1 (body number)838119 5_1.2 (part number for cluster)063309 __1.3 (coding / diagnosis / bus index) __2999 __1.4 (week/year cluster manufactured)07_150 0_1.5 (hardware / software versions) 095_06 3_1.6 (engine data)03_28_ __1.7 (ROM status)Continued short presses will just cycle you through this list again and again. The brief descriptions listedabove were provided by Jim Cash. More info might be extrapolated from the 540 OBC described at the web page mentioned above.To get out of this display and back to the index just do a 'long press' until the display changes to _teSt_ __1._again. If you 'short press' at this point you will step to _teSt_ __2._. If you continue your 'long press' (greater than 2 seconds) it will drop you right out of test mode entirely and restore your trip meter reading. The fun display is _teSt_ __2._. Go to it and pause there so you 'drop into' _teSt_ __2.0. (This is the only time the word 'teSt' appears when you're not inindex mode) Do a 'short press' here and watch the dash displays (don't worry, you won't miss it!) To get out of this wait until the gauges stop moving and do a 'long press' to back out of test 2 and into the index. Youcan't get this display to work when the car is running.If you attempt to 'drop into' tests other than 1 and 2 (without unlocking the computer) you will be immediately booted out of test mode entirely. The only exception is test 19 - the unlock panel. If you accidentally drop into it, and don't want to unlock, do a 'long press' and youwill get back out. OK, now to unlocking. NOTE: from now on, you're on yourown. If you venture past this point understand that Ibear no responsibility for anything that may happen. I'vebeen there and done that, and my car still runs fine andno magic smoke escaped. As far as I know, tests 3 through18 are displays only. Test 19 is unlock, 20 is the fuelcalibration (and I've changed mine several times as I zero in on getting the mileage right), and test 21 isRESET. I suggest you don't do a RESET, but only because I can't tell you what it does. While learning how all this works I inadvertently did the RESET. The only thing that I noticed happen was the clock in the MID zeroed out and had to be reset. What DID NOT happen: the oil changelights didn't reset. The vehicle mileage didn't change.The stereo presets and settings didn't change (I have theDSP). The heater/air cond/fan settings didn't change.I suspect you would have more grief if you disconnected the battery. But I don't KNOW if anything else happened,so I recommend you don't do it. If you accidentally pause at test 21 and 'drop into' it, the display will say 'RESET'. Nothing has happened yet and won't unless you do a 'short press'. Simply do a 'long press' (press and hold) and you will be popped out of test 21 without reseting.Enough waffling. Here's how you unlock. You have to bepaying attention because it can be a bit tricky. Stepup through the index to _teSt_ 19._ as described above.Pause there (don't press) and allow it to 'drop into' test 19. You will see a display that consists of a large 'L' followed by the words 'on' and 'off' flip-flopping back and forth. Watch it for few seconds and when the word 'off' pops up press the button and watch for the display to change. Should require just a short press. Be ready to do another short press right away, because usually the display will change to _teSt_ _0._. You don't want to pause here and 'drop into' this test 0 because if you let that happen you will be booted right out of test mode entirely. So you jump in with however many short presses you need to move through the index to get to the test you want. You can stop at any one, even 1 and 2 (which won't be any different in unlock mode). You can back-out of anytest you are in (and get to the index) with a 'long press'. While in the index another long press will takeyou right out of test mode entirely. If this happensyou become 'locked' again and have to do the 'unlock'thing all over again.I'll skip the other tests for now and get right to theonly one (besides 21-RESET and 19-UNLOCK) that allows you to change anything: test 20 - fuel factor. While unlocked step up to _teSt_ _20._ as described above and allow it to 'drop into' _20.0_ You will seeyour current fuel correction factor displayed there as a four digit number - probably '1000'; I think that is the default. You can sit there and look at it, it doesn't start changing by itself. If it is not 1000 you should write down what it is for reference. If you want to back out without changing it just press and hold the button('long press') until you pop out of test 20.Changing this number works like this: If you 'short press'once while the number is displayed you change from panel20.0 to 20.1 and the '1's digit starts scrolling. Whenit gets to what you want it to be quickly do a 'shortpress' to advance to panel 20.2 - where the '10's digitwill start scrolling after a second. When that gets towhat you want quickly do a 'short press' and move topanel 20.3 which will scroll the '100's digit(s). Whenthat gets to what you want another 'short press' putsyou back to panel 20.0 where you can admire your efforts.If you're happy with what you have set, do a 'long press'at this point and pop out of test 20. A furthur long presswill get you right out of test mode if you're done.Before getting out of test mode entirely I usually 'dropinto' test 20 again just to verify my changes are stillthere. Don't be surprised if this takes a little practice.You can go to whichever digit you want to change withoutchanging others by quickly stepping over them with quickpresses of the button. The number has to be between750 and 1250 (according to Peter Glaskowsky's 540 OBCweb page).What should you change the number to? Well, a startingpoint would be to do a percentage. If you figure yourOBC is giving you an mpg figure too high by 5%, increasethe factor by 5% from 1000 to 1050. It will take a whileto get it right because you should change it right when you do a gas fill-up and do a compare at your next fill-up.My OBC was high (optimistic) by approx. 1 mpg so I changedit from 1000 to 1050. Next two tankfulls the OBC was low by .5 mpg so I changed it to 1032. It's still off a little so I'm going to set it to 1035. You will probablyhave to check it over several fill-ups to average outinconsistencies in your fill procedure. Back to the other tests (3 through 18). While unlockedyou can check out these other displays by 'droping into'them. For each one you should try a few 'short presses'to see if there are sub-panels in each one before doinga 'long press' to back out and select the next test.To get the most out of some of them the engine has to berunning or the car moving. You can start the engine orshut it off and stay in the computer as long as you don'tturn the key right off. The brief descriptions for each test listed below were found in a post in the bimmer.org E39 forum by 'slc1230'on October 21,1998. Some of these may be wrong or changed since that was back in 1998. (stuff in brackets are my comments):- test 3 (3.0-3.1)is european inspection data - test 4 (4.0)is momentary fuel consumption- test 4 (4.1)is fuel consumption per hour- test 5 (5.0-5.1)is distance consumption - test 6 (6.0-6.2)is fuel level inputs- test 7 (7.0) is coolant temp - test 7 (7.1) is outside temp - test 7 (7.2) is engine speed (digital tach!)- test 7 (7.3) is vehicle speed (digital speedo!) (kph)- test 7 (7.4) speed again, matches optimistic speedo (new-2001 only?, 530 only?) - test 8 (8.0-8.3)is hex codes- test 9 is battery voltage- test 10 is country code- test 11 is cluster code- test 12 is not used- test 13 is gong test- test 14 (14.0-14.6) is error memories- test 15 through 18 not used Compare the above with the info on the 540 OBC at theweb site I noted at the beginning of this essay.
