2014 i3 Rex faults

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Emma Matthews

New member
Dec 21, 2023
It’s been 6 months, 1000s of $ and still my i3 is not fixed. Here’s the summary from BMW.
Any suggestions on how to fix?

Initial diagnosis and repair:
Upon inspecting your vehicle for the active drivetrain warning on the dashboard, we conducted a thorough diagnostic scan. Following this inspection, we identified fault codes relating to the RDME control module and intake pressure sensor.
To resolve the problem, and given its potential impact on the RDME, we advised to replace the intake pressure sensor, hoping for a more cost-effective repair. Unfortunately, the warning light persisted and the RDME was confirmed as requiring replacement.

The RMDE was then fitted to the vehicle and tested. The vehicle has been driven for approximately 3,000km’s and then again, an engine warning light has shown.
Secondary diagnosis and suggested repair:

Following your vehicle’s return, our Master Technician reviewed the previous work and repair history on your i3. The diagnosis identified the engine crankshaft sensor had a fault. The engine crankshaft sensor determines the position and rotational speed of the engine crank could be contributing to the intake/ambient engine pressure fault now that the RDME replacement has enabled the petrol engine. As we can now start the petrol engine however every time that it switches to petrol mode, the engine cuts off. We replaced the crankshaft sensor which has now addressed the intermittent RDME fault and allowed the petrol engine to run however there the petrol engine has now lodged faults for the camshaft and a misfire on cylinder one.

In reference to our earlier diagnosis, our Master Technician has highlighted that the presence of the RDME fault in the vehicle would electronically deactivate the range extender (petrol engine). After replacing both the RDME and crankshaft sensor, the petrol engine is now enabled. However, a new wall has been hit – the petrol engine deactivates as soon as it attempts to take control. Drawing from extensive experience, our Master Technician suspects that the most plausible cause is a component known as the torsion splined shaft within the engine.
Our primary concern revolves around the removal of the torsion spline from the engine. The unique operation of the torsion spline involves it being compressed under stress. Once this component is taken out, it typically requires replacement irrespective of its condition. Ideally, if the vehicle's issues are solely linked to the torsion spline, replacing it would be an optimal solution. However, there's a potential complication. The removal of the torsion spline might reveal more than just a worn or stressed component. There's a chance that the torsion spline could be splintered, leaving debris in the engine or possibly causing damage to the engine camshaft. To assess this risk we removed the undercarriage engine oil sump, where all the engine oil is stored. Fortunately, there is no apparent evidence of metal filings or debris, which is an encouraging sign. With that being said, it's crucial to acknowledge that the absence of visible debris doesn't guarantee the torsion spline's integrity. Once the torsion spline is removed, the vehicle becomes inoperable without a replacement.

Going through BMW’s repair instructions for the torsion spline, they also advised to replace the Starter Motor Generator if the run-time of the Starter Motor Generator exceeds a certain run-time and your vehicle has doubled this amount. Now, the vehicle may run perfectly fine without a new starter motor generator however we do not know if this will be the case. The reason for BMW recommending the replacing the starter generator is that the splined teeth of the torsion spline will wear down the teeth on the starter generator over time as the replacement of the splined torsion paired with an aged starter Motor Generator may cause complications.

Going forward, we are going to have a sit down with our Master Technician and Workshop Manager to formulate some options for repair. We have priced up replacement parts for the procedure that the Technical BMW diagnosis has advised and the parts cost alone even at a special rate would still be $5935.28 including gst. I’ve reached out to several 2nd hand parts suppliers as a second-hand engine replacement may be a more viable option.