got a 99 tahoe no start. Drove fine one day, that night the ol man left the charger on overnight, went to crank her--no start--turns over like its 180* off. coughs and backfires into intake. My thinking is protection device for ecu shorted and in turn shorted ecu. Got fuel and spark. no engine codes. Will almost start, but then stumbles. any ideas? she got 250k on her