It HAS been said before, by me several times
, but these cars are seriously sensitive!
WAY to sensitive if you ask me, but there's 15 "computers" in the R171 and 30 (!!) in the R172.. The battery is at the heart of this. If any of the computers don't work properly (for whatever reason, in this case maybe power?!), then you'll get these .. "weird" issues. Almost impossible to pin down, there's seldom any actual triggered errors to go by.
I recommend getting a name brand battery, instead of that .. whatever that is!!
Also, AGM batteries have been noted not to .. "work as it should" (weird errors, gone away once it was replaced with a "normal" one). Some swear by it, some have had issues..
Also, don't cheap out on the power. I got a Varta Silver 74Ah for my 55 and it was MUCH more responsive after that. My old battery was not at all bad (I HAD gone too low a few times - although not zero!), which takes a toll on the battery over time. It was a few years old, so I changed it anyway, just because I wanted peace of mind. Don't go below 70Ah, that's IMO just borderline..
Considering how "cheap" (all things considered) a new, PROPER/KNOWN-GOOD, battery is (I payed £93 for mine, which is a bit steep but by no means horribly more than any other, cheaper brand), I'd recommend replacing it "just because". It should be done regularly anyway, because of aforementioned considerations.
Don't go cheap, this is a high performance sports car, it deserves good quality parts. No point in trying to save £10, £20 or even £30 when it's very likely to be a problem in the long run..
If the error/problem persists after that, at least you know it's absolutely not the battery, and I'd start looking at replacing those sensors. Again, "just because".
We're usually VERY resistant to "replace parts at random" here, which is very good and correct. BUT, there are parts that "should" be replaced, "just because"
. Just because they're very likely to be a problem, they're very likely to cause issues "shortly" (if they're not already!
), because it can be very difficult to pin down the error to something specific, and are known to go bad, AND that are cheap enough that it won't cause an economic ruin. EVEN if you have to get a professional to replace them for you. But both of these are simple and quick enough, so even if you only have a basic knowledge on how to use a spanner, you can do it. Maybe with a bit of guidance, but still
They're only about £40 a pop. Not sure how many you have, but I have one of each in my 55 - some have two CAM shaft sensors. Not sure which engines have that though..