CM 870 Engine Brake

[Truckdriven]

I have a cm870 with 2 jake solenoids, howenver only one will come but occasionally after several seconds of engine brake the second one will come on. Watching the commanded output with Insite it only shows one on and if the second one comes one the commanded output goes right with it. Could it be sensor inputs that are doing this? Does the ecm monitor resistance on the solenoids and not turn them on if they are bad? I only have a coolant level sensor fault but don't see any relation with that. Demandate was done by RR