2004 W211 E240 Estate ABS, ESP & Service Brake Malfunction

[Chazof the west]

On turning on the ignition I get all of the above and the orange abs light on the panel. Drives and stops as normal. I've changed the secondary battery as the original was still in situ and get 12.67v. The earth tab near the abs controller is good. The fault is occasionally intermittent and disappears when the car has been stood in the sun! It also cleared for a short period after I disconnected the earth tab.

My eBay OBD Code reader doesn't show any faults. Before I splash out on a STAR session are there any other places I should be looking? TIA