I started my blazer up and it was running fine for about 30 sec then it just shut off and won't turn back on, I'm getting fuel I no for a fact, just no spark. My icm is good had it tested and my coil pack is good as well. I replaced the rotor and distributed cap, iv checked all relays and fuses. I had it towed to auto zone and they came up with 2 codes on it that were low voltage to coil pack and my icm witch was tested and just fine, iv been told it might be my ecm but would a bad ecm cause no spark? Been working on it for a week no and haven't got no were with it dose any body no any ideas of what the problem is? Please help