Engine Light Signal for 2005 PCM swap (Page 1/1) Yorgle JUL 03, 03:53 PM I understand that the Fiero ECM grounds the engine light bulb on the dash to turn it on. Does anyone here know if the later GM PCM's worked the same way? In other words, on my 3400 (from a 2005 Impala) swap, can I simply disconnect the signal wire to the light from the FIero ECM and instead hook that wire directly to the MIL pin on the Implala PCM? I was going to simply try it, but I don't want to risk sending 12vdc into a pin that's not expecting it. olejoedad JUL 03, 11:34 PM Yes, the PCM supplies the ground to turn on the MIL lamp.