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Car Forum / BMW Cars / May 2007M70 oxygen sensor diagnostics
I have an intermittent check engine light, on my 1991 750iL. I have the Bentley manual, that describes the connector location as beneath the transmission. Is there any easier location to check the voltages to the sensor heaters, and the sensor output? The check engine light used to come on on the first hill a mile or so from my house on the morning commute, but now it comes on immediately upon startup, and sometimes goes out after highway driving. I used the manual method of reading out stored engine codes (pumping gas pedal 5 times right after turning on ignition, observing sequence of flashing 'check engine light'), the output is 1444, which I believe means everything OK. I had the vehicle to a dealership before for the check engine light, and they replaced one of the O2 sensors, upon picking up the car, there was still a check engine light, but with different behavior, in terms of when it turns on. When I returned the car to the dealership, they claimed the check engine light was due to a slipping transmission. I since had it serviced, and noticed that the harsh down shifts when coasting 40-45 mph went away, I am unsure whether the slipping transmission engine code was reset. But the check engine light never went away. My gas mileage, is 13mpg (US), in a commute with 50% highway, 50% local roads. Are there conditions that cause check engine light to come on, without storing a code? Is there indeed a slipping transmission engine code for a 1991 M70, or is the BMW dealership simply blabbering to cover incompetence? Any other suggestions for how to troubleshoot this problem? Jan Fure > I have an intermittent check engine light, on my 1991 750iL. I have > the Bentley manual, that describes the connector location as beneath [quoted text clipped - 33 lines] > > Jan Fure ----- <to the background blabbering> The check engine light is emissions -related, not transmission problems. And why the HELL didn't the dealer mechanics tell you that the first time? Bunch of jack-offs! Am I wrong here... anyone? My guess is you need both O2 sensors replaced and both ECUs reset. I say both because the v12 has 2. That's right. Some would say disconnect the battery for a few minutes and you're good to check if the light went out for good. This would be a good time for a trans fluid and filter change, DIY, of course. Can anyone back me up on this? Bill in Omaha '86 535i >> I have an intermittent check engine light, on my 1991 750iL. I have >> the Bentley manual, that describes the connector location as beneath [quoted text clipped - 16 lines] >> >> When I returned the car to the dealership, they claimed the check > ----- > [quoted text clipped - 11 lines] > Bill in Omaha > '86 535i I would agree Bill. The first thing I would do is change the other Oxygen sensor as well. You can reset the the ecu's in the way you mentioned or by another proceedure layed out in the repair manual for the car. I am about to change my sensors in my 850 because I am experiencing the same thing as Jan at the moment. There is a fair bit of coverage on this topic in the 8 series forum. Same engine with many of the same problems. Dave > >> I have an intermittent check engine light, on my 1991 750iL. I have > >> the Bentley manual, that describes the connector location as beneath [quoted text clipped - 46 lines] > ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** > ---------------------------------------------------------- ----- Most of the info I culled from the WWW is somewhat model-interchangeable. That's one reason I like BMW. I need to do a sunroof replacement soon due to a PITA tiny rust spot. I'll be swapping in a glass section from... SAAB! I found several articles and DIY, plus there's a yard here in Omaha with 5 donors. Not a lot of folks know about the 2 ECUs for the v12s. Kudos to all those folks who provided info that has helped me and those I've given the info to. I guess my computer surfing time does pay off. Bill in Omaha '86 535i >>This would be a good time for a trans > > fluid and filter change, DIY, of course. Can anyone back me up on [quoted text clipped - 11 lines] > the same problems. > Dave Update: shogun from a BMW forum gave me this useful reply: http://www.bimmerboard.com/forums/posts/351877 and after stomping 6 times, I get a flash code for the left half of the engine (DME2/cyls 7-12), from which I got code 2221, which means oxygen sensor. This one might be replaced under warranty, as this is the same sensor as I paid BMW to replace for me last year. Jan Update: As mentioned in other post, the stored codes can be read out by stomping gas pedal 5 times for DME1, and 6 times for DME2, which represent cylinders 1-6 and 7-12 respectively, only when I learned about 2 manual readouts being needed, did I know for sure I had an O2 sensor code. Dealership fixed the oxygen sensor code under warranty. Problem: Oxygen sensor connector loose. Why: That's the way it was installed by dealer. Why was it not addressed before? When I first complained to dealer that they did not fix the check engine light, they blamed it on a slipping transmission. Is this dealership-incompetence, or a deliberate attempt to empty the wallets of 7 series owners? Jan Fure > Update: > [quoted text clipped - 18 lines] > > Jan Fure ----- I noticed that women, and some men, are treated differently by the dealer/mechanic, esp. BMW owners. We tested this and my wife was the helper. We even used the same car! You know, I ain't sayin' one way or another, I'm just sayin'. Not everyone is like that either. Jan, I'm glad the problem is finally resolved and I wish you didn't have to experience it that way. I do think the dealer has a "ditz-o-meter" they aim at incoming customers to determine how gullible they are to over-priced, mis-diagnosis that fixes nothing correctly. Bill in Omaha '86 535i >> Update: >> [quoted text clipped - 32 lines] >Bill in Omaha >'86 535i Bill (and all) All vehicle owners/operators are guilty of being "EXPERTS" so as not to appear a complete tosser (jerk). Why? It's a macho thing. "Me - I am a MAN and I know EVERYTHING there is to know about cars (that's why I am asking you to fix it??)" The Stealer or mechanic will suggest something that MIGHT be the problem - in my case the PDC wasn't working on my E39 740i. My instructions went exactly like this........... Service guy: Can I help sir! Me: My PDC has packed up - can you fix it? Service guy: Certainly sir, let's get the paperwork done Wait until we get the vehicle details on the job sheet etc. Service guy: Sign here please Me: Why? Service guy: We require the authority to carry out the work. Me: What work? Service guy: What I have put on the job sheet Me: Sorry my friend (presumptuously) I have no idea what this means (NOTE - after 30 years in the auto business I do know exactly what it means) Service guy: We will replace the PDC electronic control unit Me: Will that fix it? Service guy: It should do Me: And if it doesn't? Service guy: We will have to try something else Me: Of course if the PDC - control unit is not the problem you won't charge for it? Service guy: Sorry? - lost for words........ Me: I take the job sheet and cross out all the bollocks about swapping Control units and such like and write across the sheet in capital letters "PDC not working - FIX IT" Service guy: Excuse me - goes and gets service manager. Manager: What's the problem? Me: My PDC is not working - can you fix it? Manager: Yes Sir! Me: With no mumbo-jumbo bollocks about me authorizing you to do something that I have not the faintest clue that you are talking about. Manager: Certainly sir - passes job sheet to service guy exactly as I cancelled the crap and wrote FIX IT. Collected car same day and needless to say - PDC didn't work after they swapped the PDC control unit. I didn't pay and booked the car in for another day. Arrived to collect car on the second day and found it had not moved from the parking place I left it - How do I know? I had parked on an Ice lolly (pop) stick and noticed it when I left the car - exactly the same when I got back. I hit the roof - time wasting, incompetence etc. I was offered the Service managers M5 to pacify me and left the car there for 6 days until they fixed it. Cost --------- You'll never believe it. £52 ($100 roughly in today's money) What for? - 1 relay and a connector. MORAL ------------- Never agree to ANYTHING except "CAN YOU FIX IT" You are NOT an expert and know nothing of how it works (even if you do) - if you agree to having a new gearbox then that's what you pay for when you probably only needed a replacement clutch. Wake up guys! > Bill (and all) > [quoted text clipped - 82 lines] > > Wake up guys! ----- If I may... I always take full responsibility for my car, my knowledge (or lack thereof...<chuckle>), and my actions. I ranted pretty hard here a couple of months ago about folks who have BMWs, but probably shouldn't. I think the thread was "armchair" something. Anyway, nothing against Oscar, Jan, or anyone here, but I often get the impression some folks who post here, especially the "grammar-challenged", just want to be hand-held with their car's problem and have no desire to understand the situation. We (the readers and contributors) often don't even get the bare minimum to troubleshoot the problem. Model, year, engine/trans, location in the world... you know the drill. Oscar's story above is an example of what I mean about some shops who "repair" our machines. I thought OBD-II was supposed to help curtail some of that crap. <slapping head> Stoopid Bill! I find that as I get older, the level of competant people is going down. Things and people are becoming too replaceable and throw-away. Where has "expertise" gone? So... that's why I make all the info I have available to others. Maybe someone can be saved from the PITA trouble-finding expedition I went through. At the same time, I hope they also care enough to really get something out of it besides "WHAAA! fix it for me! I don't want to give a sh.t about this problem!" Then next time it happens to you or someone you know, you can CONTRIBUTE TO THE FIX INSTEAD OF THE PROBLEM. Damn, I started another rant. I kinda like answering the questions on here and I hope I fixed more than I broke. I just wish I was getting paid for it! HA! Bill in Omaha '86 535i >> Bill (and all) >> [quoted text clipped - 124 lines] >Bill in Omaha >'86 535i Bill In my Alta-ego I am a technical teacher in what you would call a "high School". I teach electronics and engineering to complete idiots who will remain that way for the remainder of their lives. If it don't use batteries or can't be recharged they are not the slightest interested. If it hasn't got a phone in it they cannot play with it. The Gov' rules state what we should teach them unfortunately they don't state what they MUST learn so they learn NOTHING by choice. We must teach them HOW but not WHY which is the root cause of this nanny society and no handbooks in the car - why put handbooks in the car - they can't or won't read them. > The Stealer or mechanic will suggest something that MIGHT be the problem - in my > case the PDC wasn't working on my E39 740i. > Wake up guys! ---- E38 740i, "expert". <said with humor> Bill in Omaha '86 535i >> The Stealer or mechanic will suggest something that MIGHT be the problem - >in my [quoted text clipped - 6 lines] >Bill in Omaha >'86 535i Hi Bill Been there done that now got the 740i and a new E65 730d SE |
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