Posts: 1
Joined: Sat Dec 28, 2019 8:02 am

Rex only runs once the engine compartment fan is running

Sat Mar 21, 2020 10:40 pm

Hello All.

I have owned a 2014 Rex since the fall of 2017. For the past year and a half, I have been regularly receiving the "Drivetrain Error: Note Remaining Range" message about 30 seconds after the car is started. When I look up the error message in Check Control it says: "Only electric driving possible, limited range." I am assuming that a sensor is tripped during a self-diagnostic cycle at startup, as the error message appears at exactly the same time whenever I start the car (regardless of SOC). The CEL also illuminates when I receive this error message.

I have coded the hold state of charge function. Interestingly, I can start the rex in emissions mode or by holding state of charge, as long as I initiate the hold within the first thirty seconds after pressing "Start" so as to "beat" the Drivetrain message. Once I have received the Drivetrain message, I cannot start the rex in either emissions mode or by activating the hold state of charge function until I cycle the start button and clear the message.

But here's the kicker: the rex will only run once the engine compartment fan is running. Prior to that, the rex will start but then shut off at the same time I receive the Drivetrain message. Once the engine compartment fan is running, however, I can start and stop the rex at will in emissions mode and also turn the rex on while driving by holding the state of charge (as long as the SOC is below 75%) without receiving the Drivetrain message. Indeed, as long as the engine compartment fan is running, the rex runs for as long as I need it to and I can cycle the start button and not receive the Drivetrain message at all. Once the engine compartment fan turns off, the Drivetrain message returns.

The rex itself appears to be working properly--providing adequate charge, not misfiring, etc.

The car has had a host of unrelated problems, but this is the one that I have not been able to solve. In my attempt, I have replaced the fuel pump and fuel pump relay. I have scanned for OBDII codes using a Vgate adapter and OBD AutoDoctor and nothing turns up. I have tested the voltage going to the two temperature sensors in the engine compartment and they are in spec (5 volts). I have also tested the resistance of the two temperature sensors and they appear to be functioning properly (ie. the resistance drops as the sensors are warmed and vice versa).

I have managed to essentially drive the car as a BEV over the past year and a half, however, a change in circumstances requires that I utilize the rex for a longer commute.

Anyone have any ideas on a cause or other diagnostic tests I can run?

I have looked into purchasing Bimmerlink to be able to pull the BMW specific fault codes, but am not sure of its functionality with the i3. I have reached out to the developer with that question, but have not heard back yet. Anyone know?

I look forward to your thoughts!

Thank you.

Andrew Cole

PS. Here's the engine compartment fan that I am referring to: ... 1VnXlOJVOv

And here are the temperature sensors: ... 1VnXkd50oQ

Posts: 4837
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Rex only runs once the engine compartment fan is running

Sun Mar 22, 2020 2:28 pm

If the engine coolant sensor is messed up (sensing that it's hot and needs the cooling fan to run), there's probably an interlock to prevent the engine from running unless it sees the fan running.

If it's that, it could be a corroded connector, broken wire, loose connection, or a bad sensor.

Could be other things, too, I suppose. This comes to mind first for me, though.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

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