m3 e46 gear position sensor problem

I have a 2003 m3 with the yellow cog light on. Replaced gear position sensor twice and the problem still persists. I have reset the light with icarsoft scanner. It comes back on after reset. I have tried 4 different salmon relays, no difference. The car shifts and drives fine but can not get rid of cog light. One answer was to check compression spring. What is this and where is it located. Any other advice will be helpful.