Daytime running lights not working

Hi-A few weeks ago the daytime running lights on my Pontiac Grand Prix Gt 2000 stopped working. I was told by my mechanic that there could be a problem with the DRL module. I checked with a friend at GM,and he told me that it was very rare for there to be a problem with the module. He told me, that right beside the module, under the dash,there was a diode,and he said that the doide would burn out first,because it was there to protect the module.Is this true,because I would like to know which one I shoud change,because the module is $400.00, and the diode is $50.00.Is this true what I am told? Thanks Russell.