M5V8 337 Report post Posted July 28, 2013 (edited) Help!!!!! Cruising home the M5's gone into limp mode. (not even driving fast at all!! Honest!) Nothing over 3000rpm. No warnings nothing. Turn key off & on its ok. Then almost straight away the same thing. 1/2 tank of gas (always 98) Get home scan Codes: 81 - low fuel cat protection (I think) 58 - post cat o2 voltage (always get this one) 25 - precat 02 heater 26 - precat o2 heater 27- aftercat o2 heater 28 - aftercat o2 heater Reset & go for a drive & it's ok again. What the hell?.. I've got a big drive coming up in two weeks I can afford to have this happen again. Anyone know why the cat system might put the car into limp mode? or is it a fuel pump failing? things done recently: - spacers on the post cat sensors thanks to ray for sourcing them - new fuel filter - new OEM MAF's - replace pre-cat sensors with OEM bosch items (yes i pluged them back in the right way, since I only replaced the pre cats it was pretty easy) Edited July 29, 2013 by M5V8 Quote Share this post Link to post Share on other sites
yng_750 247 Report post Posted July 28, 2013 could be a fuel pressure issue? i thought each side of O2 sensors had their own entire circuit of heaters with separate relays etc so shouldn't be common so have the same errors on all the sensors. Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted July 28, 2013 (edited) i replaced the fuel filter a few weeks ago. But the car was fine all the way over the hill yesterday which is weird. She was out overnight and it got really cold. This is not normal for her. But driving back over the hill she was fine going up, following some grandpa really slowly on the way back down the other side, when to pull out to finally overtake and nothing. Could it be i was driving too slow down a steep hill? but seriously..... maybe a failing fuel pump? or bad gas? can a failing post cat o2 sensor do this kind of thing? I haven't replaced the post cat sensor as I figured this was just to monitor the health of the cats. Could a damaged or short circuit on a sensor cause this issue? I am considering dropping her off to the BMW dealership next week for a full inspection 2 service. She's probably only 5000km off being due anyway. Edited July 28, 2013 by M5V8 Quote Share this post Link to post Share on other sites
yng_750 247 Report post Posted July 28, 2013 coasting can cause issues with vacuum being strong enough to cause vac leaks on the intake, this can make it run lean and throw out your mixtures but the ecu should be able to manage this, shouldnt screw the o2s clear codes drive and see if codes reappear. Quote Share this post Link to post Share on other sites
yng_750 247 Report post Posted July 28, 2013 i had a 740i that went into limp mode one day when i was crawling up a very steep hill at 5kph behind a truck (stupid hill in cambridge) pulled over turned car off, restarted and it went fine, never missed a beat again. think it was the slow pull made it think gearbox blew? dunno Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted July 28, 2013 (edited) when we got down on the flat I turned off & on and it would rev fine. pulled out accelerated and it went into limp mode again. Turned it off at the next red light. Again as soon as it reved over 3k,..... limp mode. So it would do it over & over. Limp mode literally just got us home. Even in limp mode the motor sounded fine. Got home. Cleared codes. Went for a rip up the road and it's normal again. No sign of any issue. We are out for dinner tonight so I think I will take the M5 for another drive see if it happens again. Very freakin weird. Thing is I don't want to just drop it a Jeff Grey & say find the fault as they might not find anything and hand me a bill for squillions. Edited July 28, 2013 by M5V8 Quote Share this post Link to post Share on other sites
euroriffic 607 Report post Posted July 28, 2013 hows your battery? Have heard these can cause issues if theyre getting flat, and especially if your going slow so the altinator wont be charging fully and drawing more current off the battery. Quote Share this post Link to post Share on other sites
1rotty 40 Report post Posted July 28, 2013 Try giving it a battery reset. Disconnect both battery caables.....tape the terminals together(well away from battery terminals). Leave for 30 mins or so This drains all the capacitors relays etc. Same problem on a 740......this solved it Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted July 28, 2013 (edited) just came back from dinner. freakin did it again. Battery is good. Prob 6 mths old. I'll try the battery disconnect / reset thing tomorrow along with removing the post cat spacers see if that makes a difference. Also I believe there is a heater fuse in the engine bay? Edited July 28, 2013 by M5V8 Quote Share this post Link to post Share on other sites
Jono51 59 Report post Posted July 28, 2013 (edited) just came back from dinner. freakin did it again. Battery is good. Prob 6 mths old. I'll try the battery disconnect / reset thing tomorrow along with removing the post cat spacers see if that makes a difference. Also I believe there is a heater fuse in the engine bay? Darren, what scan tool are you using? and is it capable of live data? you seem to have replaced a lot of parts lately for was it a hesitant fault? what was original scan results from this, im sort of wondering wether a new fault has been introduced, so you may now have several Edited July 28, 2013 by JKSE Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted July 28, 2013 (edited) Hi Jon, no i don't think so. I have the peake research tool. I changed the precat 02 & MAF because the car was occasionally stalling out. This solved this issue. Originally the scan only showed bad voltage from post cat 02 sensors which is why i added the spacers in on Ray's advice. I did find some good information last night there is a fuse for the 02 heater system under the cabin air filter box in the engine bay. apparently if this blows you get code 81 & the 02 pre heating system wont work. it is possible the spacer has made the post cat 02 sensor wires short something which I will need to get under the car to confirm. i'll throw this in there too, the alarm randomly went off last wk too. in the garage. No idea if it's related or not. Edited July 28, 2013 by M5V8 Quote Share this post Link to post Share on other sites
hybrid 1043 Report post Posted July 28, 2013 Did you reset the adaptions after replacing the MAF. This is something your not suppose to do on a whim, but after replacing components critical to the calculation of the fueling it is imperative that this is completed. Next thing to check is if you have a vacuum leak on the intake side. Agreed on the live data. Measurement of the OS sensors and MAF values then looking at the adpation values and 'rough idle' state. Are these values going out of range. Now, resetting adaptions will probably do a couple of things, on first start, put the car into limp mode again (just switch off and restart) and pink like hell until you take it for a nice gentle drive to learn adaptions. After about 10 mins you can nail it to relearn the rest. Also as others said, get the battery checked. Doesn't matter if you think its new. Have a proper load test done to it by a specialist you trust. Also is it a proper DIN88 battery? Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted July 28, 2013 (edited) Did you reset the adaptions after replacing the MAF. This is something your not suppose to do on a whim, but after replacing components critical to the calculation of the fueling it is imperative that this is completed. Next thing to check is if you have a vacuum leak on the intake side. Agreed on the live data. Measurement of the OS sensors and MAF values then looking at the adpation values and 'rough idle' state. Are these values going out of range. Now, resetting adaptions will probably do a couple of things, on first start, put the car into limp mode again (just switch off and restart) and pink like hell until you take it for a nice gentle drive to learn adaptions. After about 10 mins you can nail it to relearn the rest. Also as others said, get the battery checked. Doesn't matter if you think its new. Have a proper load test done to it by a specialist you trust. Also is it a proper DIN88 battery? The battery is new and was load tested by AA when they installed. But I can check again. The MAF units have been in the car prob about 5000km now. No issues. Pre cat o2 sensors prob 2000km. Again no issues during this time. I'm not sure what you mean by resetting adaptions. can this be done by disconnecting the battery? Edited July 28, 2013 by M5V8 Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted July 29, 2013 (edited) Woohoo. This was doing my head in so I skipped home at lunch. Yep. Blown 30amp fuse in the little fuse box under the passenger side Cabin air filter. Replaced & cleared codes again & drained power. Ill test drive it this afternoon to confirm. Thanks for the input. To anyone with a e39 in limp mode with code 81 showing on a scan. Check this O2 heater fuse. here: http://www.bimmerfest.com/forums/showthread.php?t=679306 Edited July 29, 2013 by M5V8 Quote Share this post Link to post Share on other sites
hybrid 1043 Report post Posted July 29, 2013 Good stuff BMW insist when a MAF or other item involved in the calculation of adaptions is replaced that the adaptions are reset in the DME. You need BMW specific software to do this properly. Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted July 29, 2013 ok cool. thanks. I've booked her in for inspection 2 service thursday so will ask them to do this then. Quote Share this post Link to post Share on other sites
Jono51 59 Report post Posted July 29, 2013 ok cool. thanks. I've booked her in for inspection 2 service thursday so will ask them to do this then. just got to the laptop now, things got hectic so didn't respond quick enough to your post fortunately someone chimed in, let us know how it turns out cheers Jon Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted July 29, 2013 cheers jon. I propped the car up and found the root cause. Two of the wires on the post cat 02 sensor has touched the heat shield and worn away the plastic shield and shorted on each other. I've electrical tape wrapped the wires back up, pulled the shielding back up and replaced the sensor. Took the car for a burn down to the waterfront for my usual monday SPCA walk. Gave it the sh*ts on the way home. Oh yeah. she's fixed alright. Damn I love that car. Quote Share this post Link to post Share on other sites
