[Clifford Pope]

Thanks Chris, found them, looked at the connections, waggled them, they seem fine.
It's a curious and very infrequent occurence. The light has never come on while the engine is running - when it does, it just appears on the morning start-up, although perfect the night before. Cancelling it or not makes no difference, and it never re-appears if I do cancel it, until the process repeats a few weeks later.
Supposing the connections are fine, does that point to something beginning to go wrong inside a module, or can the diagnostic system itself develop a fault?