I've got the same problem. I'm using a Fanatec CSR-Elite wheel with a Bodnar SLI-PRO. I was able to revert back to v2.4e for DiRT Rally to work, but obviously this breaks things that are newer like DiRT 4 and the iRacing GRC cars.
For me, the gear indicator and both numerical displays for the time delta and timer work as they should, but the shift light indicators stay lit across the rev range with no fluctuation at all. I've attempted to manipulate the hardware settings in many different ways based off the ReadMe, but nothing changes it. I've played with the ports its reporting to, I've played with the extradata param, nothing works besides reverting back to at least fanaleds v2.4e.
It appears to be a Codie title issue only and possibly due to Codemasters looking at multiple devices, in my case the Fanatec wheel LCD and the SLI-PRO. Even with the Fanatec native support code in the hardware settings, it doesn't prioritize the SLI-PRO.
Any ideas, @Admin?