The warning light on the dial comes on when a failure is detected.
See also:
Speedometer
The speedometer A-fig. 31 - 32 shows the vehicle speed.
...
Front passenger's airbag deactivated
(amber)
Warning light comes on when front
passenger’s air bag is deactivated.
With front passenger’s air bag on, turning the ignition key to MAR, warning light
comes on steadily for about 4 s ...
“Dualdrive” electric power steering failure
Turning the ignition key to MAR the warning light on the dial turns on, but it
should go off after few seconds.
If the warning light stays on (on certain versions together with the message
on ...