We all should know that if a CMOS IC input pin is left floating, it acts like an aeriel, picking up whatever noise it likes.
I noticed I had a problem with my LCD switching into one of the table edit modes some time ago. What I hadn't thought about was that these problems started when I removed the PS2 keyboard from the car when I no longer needed it.
It seems the PS2 keyboard input has been left unterminated on my VEMS - is this because the pull-up (or pull-down) resistors in my ECU have died (they're probably on-chip, so nothing can be done) or is there a bug in the firmware which causes them to be turned off?
I seem to have fixed the problem by making up a PS2 plug which permanantly grounds the data line. It's been a couple of days now and I have had no table-mode LCD funnies. Prior to this, I could rely on at least one a day happening.
I also wonder if this mechanism would allow table corruption in severe cases - if the noise just happened to provide the right signals to edit something...