thatbbqguy
Posts: 4
Joined: Tue Sep 21, 2021 5:33 pm

2015 Rex misfire issues

Tue Sep 21, 2021 5:52 pm

Hello everyone, long time lurker, first time poster. I have an issue with the range extender on my 2015. When i go to start the rex, it will fire up for a few seconds and idle. But as soon as the rpms increase it will shut off. I am getting misfire codes from cyl 1 and 2. I started with the basics, replacing the spark plugs, coils and fuel pump replay. I finally broke down and took it to a BMW dealership, only to be greeted by a quote for $2200 to replace the fuel injectors, as well as remove, drain and reinstall the fuel tank.

They also let me know that they really didn't know what was wrong, and that the $2200 fuel injector replacement might not fix the issue. I can replace the injectors myself, I was already there when replacing the coils and spark plugs. Should this be the next thing for me to try? It will be the most expensive at around 400-500 for injectors after shipping. Im concerned that this dealership really didn't diagnose anything and just want me to throw money at parts until its fixed. I have done tons of research and am at my wits end.

The car is currently trying to run the maintenance cycle and failing. The rex will start and idle for about 15-20 seconds, attempt to increase rpms and then abruptly shut off with the check engine light coming on.

Not sure if it is related, but I'm also showing a rotor position sensor error, "21DD03: Electrical machine rotor position sensor, electrical: sine/cosine amplitude not possible" . I remember reading somewhere that the rex uses the output of the EME rotor position sensor to determine the rpm that the rex should be spinning at. Also worth noting that this issue came up after replacing a dead 12v battery. I used bimmercode to 'program' the new 12v battery to the car. Any info/help/previous experience from other owners is greatly appreciated. Thanks!

Neil
Posts: 65
Joined: Sat Sep 06, 2014 10:11 am
Location: Davis, CA USA

Re: 2015 Rex misfire issues

Tue Sep 21, 2021 7:24 pm

You didn't mention if you cleared the error codes. These cars can be quirky especially around bad 12V battery issues. Clear the codes and put the car to bed for the night and see if it feels better in the morning. ;)
Neil L.
2014 i3 Rex, Giga World, all the trimmings.

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MKH
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Location: Dallas

Re: 2015 Rex misfire issues

Wed Sep 22, 2021 3:59 am

That cylinder misfire error is almost always for a bad fuel pump relay. You said you replaced it? There are two relays right next to each other - might just double-check that the correct one was swapped out.
relay.jpg
relay.jpg (49.42 KiB) Viewed 1090 times
Mark H.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch Rial X10-i wheels, EVoInnovate EVSE

thatbbqguy
Posts: 4
Joined: Tue Sep 21, 2021 5:33 pm

Re: 2015 Rex misfire issues

Wed Sep 22, 2021 6:41 am

yes , forgot to mention that i cleared the codes and let it rest for a while lol. this has been an issue for over a year now. and yes i also confirmed that i replaced the correct relay.

thatbbqguy
Posts: 4
Joined: Tue Sep 21, 2021 5:33 pm

Re: 2015 Rex misfire issues

Wed Sep 22, 2021 6:56 am

the misfire codes will clear without issue, but the rotor position sensor error persists. it will not clear

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MKH
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Joined: Fri Nov 02, 2018 5:48 am
Location: Dallas

Re: 2015 Rex misfire issues

Thu Sep 23, 2021 4:54 am

the misfire codes will clear without issue, but the rotor position sensor error persists. it will not clear
That seems to indicate that this is the problem.

Looking at this NHTSA doc, appears that a possible fix is updating/reloading the EME software. Could be that the cr@ping out of the 12v caused the EME to lose the rotor position sensor values. In essence, the rotor position sensor is sending the correct position values to the EME, but the EME software now has nothing to check those values against.
https://static.nhtsa.gov/odi/tsbs/2017/ ... 7-9999.pdf
Mark H.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch Rial X10-i wheels, EVoInnovate EVSE

thatbbqguy
Posts: 4
Joined: Tue Sep 21, 2021 5:33 pm

Re: 2015 Rex misfire issues

Thu Sep 23, 2021 9:06 am

Thanks Mark, I really dont want to go back to the dealership that i took it to last time, and its the only one in my area. I assume some independent bmw shops would be able to update/reload the EME software?

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MKH
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Joined: Fri Nov 02, 2018 5:48 am
Location: Dallas

Re: 2015 Rex misfire issues

Thu Sep 23, 2021 9:13 am

I assume some independent bmw shops would be able to update/reload the EME software?
I would think so. Pretty sure it is part of the BMW ISTA online technical service software that any serious bmw shop subscribes to, for vehicle diagnosis and repair.
Mark H.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch Rial X10-i wheels, EVoInnovate EVSE

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