» Site Navigation | | » Recent Threads | | 1999 M3 Swap 09-07-2023 10:10 PM 05-02-2024 08:18 PM 6 Replies, 405,615 Views | | | | | 07-11-2006, 04:52 AM | #1 | Member Join Date: Dec 2003 Location: Los Angeles, SoCal Posts: 77 | I've got a problem... I keep getting an Pre-Cat O2 sensor code message and lights up my check engine light. I've already replaced my O2 sensor and after clearing the code, it will come back after about 1 day of driving. Any body have any ideas what may be causing this problem? thanks | | | 07-11-2006, 01:15 PM | #2 | doesn't care about you. Join Date: Aug 2004 Location: Denver, CO Posts: 3,925 | Quote: Originally Posted by vix_98_318ti I keep getting an Pre-Cat O2 sensor code message and lights up my check engine light. I've already replaced my O2 sensor and after clearing the code, it will come back after about 1 day of driving. Any body have any ideas what may be causing this problem? thanks | Are you getting any other codes, like for the Secondary Air Pump? What O2 sensor message are you getting? (response time, heater, etc...). __________________ '99 Dinan M3 | | | 07-12-2006, 04:25 PM | #3 | Senior Member Join Date: Apr 2004 Location: Pennsylvania Posts: 218 | I was having this same problem with my car... turned out to be the diffa (spl.) unit. | | | 07-13-2006, 01:11 AM | #4 | Member Join Date: Dec 2003 Location: Los Angeles, SoCal Posts: 77 | The error code I get is 0A - which is related to the Pre-Cat O2 sensor. I was getting really poor mpg (about 15/gl) then I replaced my spark plugs with Bosh 4+. The the O2 sensor was replaced, which did improve my miles slightly. But the stupid "engine light" has come back a couple of times. What exactly did you replace Etienne (diffa spl. unit)? Can you explain that a bit further...not sure what you mean and how much did it cost you and do I have to take it to the mechanic? thanks | | | 07-15-2006, 07:28 PM | #5 | Member Join Date: Dec 2003 Location: Los Angeles, SoCal Posts: 77 | bump ANY HELP?? | | | 07-17-2006, 02:43 PM | #6 | Senior Member Join Date: Apr 2004 Location: Pennsylvania Posts: 218 | Sorry for not getting back to you sooner -- not much time to scour the boards in the past few days. (more info in my pm, but thought I'd post this here as well in case its helpful to anyone) Here is basically what happened to me. CEL was on -- code read out that the oxygen sensor was bad. Took it to a shop (not dealer) and had them replace it. about a day later the CEL pops back on -- so I go back and find out the other O2 sensor is bad... so they replace that one too. Then about another day or so the CEL is back on... reading O2 sensor. I reset it... and it stays off for like an hour. Started grad-school in philly so didn't have much time to deal with it. However, my gas mileage was going down the tubes (like 18mpg) so as soon as I could I took the car to the dealer. Turns out that the diffa (spl.) unit which if I remember correctly controls the heating and maybe the current to the O2 sensors was bad because the shop that put the sensors in spliced some wire wrong. The result is that the the ECU doesn't get a proper signal from the sensors, so it throws an O2 sensor fault. Dealer had to replace the Diffa and the ECU because both had been damaged by the spliced wire, however, that being done, the CEL is off and gas mileage is back where it should be. Quote: Originally Posted by vix_98_318ti bump ANY HELP?? | | | | 07-17-2006, 07:44 PM | #7 | Member Join Date: Dec 2003 Location: Los Angeles, SoCal Posts: 77 | Could it be that I have another BAD O2 sensor? I went the cheap route and bought mine at Autozone! It cost me about $80 and it is exactly the same OE part. I'm thinking it might be the problem? Maybe I should buy from a BMW dealer/distributor? | | | 07-17-2006, 08:32 PM | #8 | Senior Member Join Date: Apr 2004 Location: Pennsylvania Posts: 218 | Its worth a try I suppose. Though if you are spending 80 bucks anyway, it might be worth it to have the dealer test 'em for you. They will probably charge you arou 80-100 bucks for the labor. If it is the plug, I would think that AutoZone would replace it for you and you'd have a new plug. If it isn't, there is a good chance they can tell you what is wrong -- it would suck to buy a new plug and find the CEL is still on... | | | 07-17-2006, 10:38 PM | #9 | Senior Member Join Date: Aug 2004 Location: Tyler, TX Posts: 1,022 | AutoZone is not going to have any better/worse parts than your BMW dealership. They only cary Bosch O2 sensors. Did you by chance have autozone pull the codes? If you did, or if they told you an O2 sensor would fix your problems then yes, you are intitled to a refund. Otherwise they will not refund your money. Seeing as you just replaced the O2 sensor then the problem probably lies elsewhere (a faulty O2 sensor is a possiblity, but very unlikely). | | | 07-19-2006, 01:00 AM | #10 | Member Join Date: Dec 2003 Location: Los Angeles, SoCal Posts: 77 | Well....I figure this much, if the connector is bad then it could indicate that I still have a bad O2 sensor. But, since there was no splicing of any kind...I doubt the problem is elsewhere. It has to be in the sensor or connector. yes? Well I am not sure what to do next...I can either buy another sensor or just live with it until I can figure out what is causing my pre-cat O2 sensor to be giving me a faulty code! Help please! thanks | | | 10-09-2006, 07:56 PM | #11 | Member Join Date: Dec 2003 Location: Los Angeles, SoCal Posts: 77 | anyone? | | | 10-09-2006, 08:09 PM | #12 | Senior Member Join Date: Dec 2005 Location: Portland Oregon Posts: 1,363 | Well if your getting low miles, try using seafoam on your car, It improved my MPG. Did you put the O2 sensor in right, maybe its loose or just needs to be whiped off. Also to imporove the cars mpg you could change the filters (fuel Oil and air). there are tuts you can look up on this site. | | | 10-09-2006, 08:43 PM | #13 | Member Join Date: Dec 2003 Location: Los Angeles, SoCal Posts: 77 | Done all that pre-maintenance stuff. New filters, oil, plugs but no help. Where can I get that seafoam? | | | 10-09-2006, 08:52 PM | #14 | Senior Member Join Date: Dec 2005 Location: Portland Oregon Posts: 1,363 | Wellit most likely will not fix your o2 issue, but your car should run better, I got my seafoam from napa, it was like 6 or 7$ | | | 10-11-2006, 12:18 PM | #15 | Senior Member Join Date: Apr 2004 Location: Pennsylvania Posts: 218 | Any further luck on this? | | | | Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | | Posting Rules | You may not post new threads You may not post replies You may not post attachments You may not edit your posts HTML code is Off | | | |