The problem for me is that as soon as an ECU is involved, unless one is provided with access to the logic contained therein, be that either with a design function specification or access to fault codes via a obd port and reader.... One is left to either rely on ones own accrued logic as to the operation of either the kit in question or similar kit where one has found a similar fault previously..... or one is left staring at the equivalent of a black box
It can be a right pain dealing with an ECU that's locked down in any way by the manufacturer, but fortunately there are alternatives, either by replacing the factory ECU with something from one of the aftermarket people like Omex, MBE etc or by purchasing a diagnostic system based on reverse-engineering the pin data.
My Morgan has an MBE ECU which is completely programmable, not that I've ever bothered to play with it, it works fine as it is and has done so since the conversion 18 years ago. For the latter type, there are all sorts available just a quick google away, I bought the software to manage my Fiat 500 from a guy in Eastern Europe, it worked a treat, enabling me to do all the stuff that would have otherwise required a main dealer to do. Relying solely on OBDII data is ok for routine maintenance but there are more sophisticated solutions available should one wish.
