Hi Everyone
Well, I just had a thorough explanation of the issue typed out but it disappeared with the tags when I inserted the image, so the summary is below. I also can't seem to post when I input the links of forum pages I've read, nor the image of the error codes
TLDR
I am getting error codes:
P268312 "Engine coolant bypass valve 'A' control circuit high, General electrical failures, Circuit short to battery"
P126083 "Theft detected, vehicle immobilized, Bus signal/message failures, Value of signal protection calculation incorrect"
I occasionally get a "battery low" warning on the dash for both the old and new battery (I read it is a common, unfixable issue in these cars), and I believe the ugly metal rattle in the engine is the cambelt tensioner that needs replacement or something in the head gasket.
Can anyone give advice please?