Hello, I hope the following assists you.
From the description you've given this will be due to an internal fault with the instrument cluster.
The instrument cluster on the Focus is a control module and also a gateway for the different speed networks on the car. The throttle pedal signals go through the cluster to the engine management control module, when the signal is lost due to the cluster fault the engine returns to idle and the warning message is displayed.
All the warning messages appear as the various signals are interrupted by the cluster fault. Any replacement cluster needs to be programmed to the car as it is a control module and the immobiliser system needs to be reprogrammed as the cluster is part of the immobiliser system.
I hope this helps but if you have more questions regarding this let me know and I'll reply as soon as I'm able to.