$Deity only knows!!! If this is the culprit we still don't know whether the interference is being transmitted through the casing or whether it's using the attached wires as antennae. You could get a portable radio tuned in to your problem frequency and move it around the engine compartment to see if the signal strength changes. If you have access to an Oscilloscope I suppose you could check the wires out to see if they're carrying the signal too. Maybe try disconnecting the temp sensor (there may be more than one though) and see if this changes anything. If you find the management system (or any other system for that matter) to be the instigator you might be able to fit some kind of notch filter or something. There's not much point in speculating too much until we know whether it's this or not. Anyway whatever it is I hope you can get it sorted easily. Let us know how you get on.