Hello Colin,,
Although the figures were also showing with the ignition on (engine off). I went back to the car after about an hour and switched on he ignition, only the digital clock figures (in green) were showing. The background red figures had disappeared. I also started the engine to no avail.
Are fault codes displayed in this manner?, if not, how are they displayed, the owners manual is no help at all.
If it happens again I will try to photograph the images, although they are quite faint.
Many thanks for your interest, much appreciated. BTW the way RX300 is a Mk2 2003 model, so far very reliable.
Barrie