Rex is toast... Any way to stop maintenance cycle?

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Ever find anything?
Mine's a BEV so I don't have any REx problems! You'll probably need to do some internet searching yourself - I think you'll find something out there on the BimmerCode related forums.
Hello All,

I have a 2016 REX and have really enjoy it. I can see where the average person might get frustrated with it. My approach to this problem is not to start replacing parts.

You must have it properly diagnosed first. And the vehicle is designed to work with the REX working properly. Disengaging he REX will create more problems. I'm 62 years old and one thing i have learned over the years is whenever you try to use something in a way it was not designed or for you are welcoming other problems.

Proper diagnosis is the key to any physical illness and the same exists with vehicles. Take it to someone who can diagnose it properly. Take no shortcuts.

As a side note i have used the Bimmer Code app and modified my settings to cut out a lot of the crap BMW and the State of California required. Love using the REX manually as needed around town and on long trips around the state of Arizona as to avoid loosing power.

I am interested in seeing the end result of this saga.

Matthew Z.
[email protected]
Hi all I3 experts

I hope some of you may be able to help me with my Rex predicament. I have a 2015 I3 60Ah Rex model and until recently I thought it was the best car I had ever owned. But now trouble with the rex have turned things into a nightmare.

A couple of months ago the rex came on and from the noice you could clearly hear that something was not right. After a while the rex shut down and gave the Drivetrain malfunction error. I wanted to get all the "usual suspects" out of the way so I installed a new 12 battery and a new fuel relay.

Then I figured that the noise might be caused by the engine running on only one cylinder. So I put in new spark plugs and new ignition coils. But still the same.

So I gave up and took the car to the local BMW workshop. They too said it was the spark plugs or ignitions coils that were faulty even though I told them that I tried changing them. But they changed them anyways. No luck. Then they changed the fuel injection nozzles. Still the same.

They did however find out that the rex was not running at all. The noise was just the engine being turned over by the starter and not starting properly. They said that they had removed the exhaust and saw flames coming out when the rex was trying to start.

And then they gave up. They want to pull the rex out but they really don't know what is wrong with the rex and they will not give any guarantee or a fixed price for the repair.

I suspect that it might be a misaligned crankshaft censor that is causing the engine to misfire and not start at all.

So, I´ve come to the conclusion that I will have to use my car as a BEV and do without the rex.

But now a new problem has occured. The car wants to do the rex maintenance cycle and tries to start the rex, which it can´t. But it will turn the engine and cause a lot of misfire noise. Then it will give the engine malfunction error. It will repeat this with very short intevals. On a short 15 km trip it will run and fail the rex maintenance cycle twice. This is VERY annoying.

Is there any way to disable the rex maintenance cycle? As a quick´n dirty I will unplug the ignition coil wires. This will end the misfiring noise but it will not stop the maintenance cycle. Any suggestions?

Thanks in advance

- Michael Hammer
From the description of "flames coming out" when the exhaust pipe is removed, it sounds to me like a valve timing issue. I don't know if this engine has a belt, chain or gear linking crankshaft to camshaft, but that's what may have failed.
As I read in a german blog (I3rex) someone had a problem with the chain spanner on the chain which drives the camshaft. This is obviously a common problem at the early Rex. If the spanner spring is defect the chain jumps and the valves open and close at the wrong moment. In the worst case the valves can be dammaged which was the case with the german guy. At later Rex the spanner has been replaced by an hydraulic one the guy wrote. Perhaps this is the problem with your Rex too but I hope not. Here is the link, maybe you can translate with DeepL.
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A BEV without the heat pump, which would occupy the space where the gas tank was.
That may require sourcing a BEV transmission as well as the BEV mount, as the REx serves as structural member. It's unclear to me if the base transmission casting is the same or not from these two photos. Perhaps the extra casted bit of the REx mount is just a bolt on adapter.


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Hi Michael,
Sorry to hear about your problem.
Here is my humble contribution to what to do to try and solve it:
- You say you took the car to an official BMW dealership and they could not fix the problem ? This is unacceptable and I would write a complaint to BMW Germany explaining your situation and asking them for advice to how to solve it.
- Take it to another dealership to see it they can support you.
- The engine is a motorcycle engine so any experienced motorcycle workshop should be able to find what's causing the non start.
Once the gasoline engine works, the error messages with the i3 hopefully disappears.
- If an engine has air, gasoline and spark then the engine should run. Therefore when the engine tries to start need to check if it sucks ir air, that there are sparks coming out of the spark plug cable, and that the injector squirts out fuel. I believe you have air, spark and gasoline reading your post.

Then you need to check if you have compression in your cylinders. Any workshop can help you with this. If you have compression it might be the pickup sensor (I had this problem in my BMW C1 125 cc).
If you do NOT have sufficient compression, it can be worrn piston rings, valve leaks, perhaps head gasket leak (all this more likely if high mileage engines).
Although I'm more inclined to think that your engine is out of timing due to the chain skipping a tooth. You can put the engine a TDC and see if it holds pressure through the park plugs. A good workshop should be able to test all this.

There ise a diagnostic odb 2 port on the i3. Thai port should be able to diagnose the gasoline engine error codes.
A workshop (and BMW) should be able to help you with this too.

Hope you can solve the problem soon.
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Same issue here. MY BMW dealership in Austin, TX quoted me .... YOU READY? EIGHTEEN THOUSAND DOLLARS to replace REX.
I agree with what others have said, avoid the main dealer. Their technicians, no disrespect, simply don’t have the technical knowledge to fix. They communicate with BMW via a portal and they don’t tend to deviate from the repair plan. You will literally spend thousands on new parts on the premise it may or may not fix it.

The engine is a fairly basic bit of kit, so assuming it’s mechanical, then that’s the route I would take. In addition, before doing anything, then ISTA software is essential. This is basically dealer level diagnostics, so a mechanic worth their salt will be able to see fault codes and work from there. Even an extreme option would be to swap out the engine for a replacement used engine if the EME can communicate with it.