Need help truck is cutting out(lightningbolt)

ok today the lightning bolt light came on and i cleared it, then about two minutes later it cam on again, ive cleared it about 6 times and it comes back everytime. the truck will cut out every 15 secs goin down the road and when i let off the petal and let it slow down on its own i hear a loud whistle that sounds like the exhaust brake but my jake is off. any ideas? o and this light has came on before at the river. it seems everytime it comes on is in or around water (went thru puddles today)