I already checked, all Aluminum, including the piston, the material is not magnetic. the only magnetic material is the small steel dowel pins that align the piston housing and the block. I think the pistons has a built-in magnet.
something within the piston has to be magnetic, otherwise it could not work with the hall effect sensors. regardless that should cause problems based in the theory that the Jim mentioned. Well unless the two different pistons miraculously have the same exact magnetic field.
Ok, I figured I would join in on this one because my e60 is having a very similar issue with the smg. Brief history new clutch new flywheel bled numerous times at bmw dealership. Still pulls code 5506 clutch valve with intermittent red cogs that only got worse until the car would not shift to 1st or reverse even when shifter was engaged. My indy bled again and it ran for a week b4 the code came back. he now has the transmission out himself and replaced clutch control valve isolated and rewrapped the wires on the harness which were partially exposed and replaced the larger harness on top of the trans. All this to no avail. He is now going to replace the smg ecu and I will give you guys an update once I have the results.
I think it's more helpful from a thread/problem discussion point of view to create a new topic with all your issues and steps since it seems you've already spend quite a bit of time and money. 5506 code is quite a specific error and there's only so many things that can cause it, and it doesn't seem to have been remediated by the most expensive part.
Hello Tim5e60, I already replied to one post of yours on other thread. I know as per ISTA test plan to change ECU at last resort, but that is only if you confirmed you have done sequence of testing. I want to see what is the clutch valve data on the status page from ISTA/INPA and to follow the guidlines I included and report the results, also to wiggle the wiring and connectors while viewing the status page for intermittent connection. INPA has more detailes why the fault code triggered. There is also a SB refer to update the SMG ECU but that if you have fault 4F80 ( transmission) and 4F82, 4F82 is for not possible to engage R/1st gear shift rod for example, you have different fault code related to other gear shift rod pair, so the fix in this particulare fault code is to update the ECU, that only if you don't have other fault codes or other SMG failed component. It is important to read fault code whenever the SMG fail to shift gear to know what triggered that code, where and how to trace the problem. If you start replacing the ECU, just do it and lets see what happen and report back. If this the case I would reflash the ECU, I think it is the same as replacing the ECU if the ECU is not damaged, I doubt it is damage because it should thrw a code for that, so start with ECU reflash.