Originally Posted by pinballdave
I don't think anyone really knows what causes it, it could be disconnecting the battery while the ECU is still active, it could be a failure due to low battery voltage, it could be a spike while reconnecting the battery.
All we know is that these kinds of events happen all the time, I expect most of us have suffered from battery problems and/or disconnected and reconnected the battery many times, for long or short periods, and our ECUs are still fine. It's very rare but one day it could happen to any of us (at least those of us with 2.0D engines, the rest of you can just worry about the airbag CFFF error!).
The good news is that if it does happen, there's a few ways to fix it. Either take the car to Volvo for an ECU reload, or there are many third party specialists that can read the CEM data, the ABS module serial number and re-sync the immobiliser code in the ECU. (I even have the tools to do this myself!).
You seem to have a lot of threads about your issue, some talking about CEMs, others about ECUs and batteries, each with a different isolated question, and some of the answers given (including my own) are appropriate for the question asked in the particular thread, but given the whole picture a different course of action may be more appropriate.
I'd suggest choosing one thread, and updating it with all the details of the problems you've had, the things you've tried so far, and then keep all new questions and comments in that one thread.
From your thread with all the fault codes, a lot of them appear to be related to can bus communications. This is a common problem on these car models. The suggestion of checking the CEM for corrosion and cleaning the contacts of it's connectors, can be a quick fix for this problem, but it's more likely to be due to a few connector contacts in the wiring to the CEM that were poorly specified by Ford and are a weak point, if these are not replaced, then the fault can re-occur.
Sometimes it can be caused by a worn out battery, or a failing alternator causing electrical noise on the communications bus.
But it's very rare for it to be one of the electronics modules themselves. So removing them and sending them out for testing, before checking and addressing the common causes is unlikely to be productive.
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