Chrysler 300C CRD - accelerator warning light coming on - Joe 1942

Accelerator warning light coming on, was infrequent and switching off ignition and removing key, waiting 10 seconds and starting up again - like rebooting a computer- seemed to work. Now warning light more frequent and sometimes going into limp home mode. Car has been into main dealership in the past (this has been a long running problem) but no faults with accelerator have been logged. Also been to independent garage but fault not found.