Wouldn't problems with the actuator set a
DTC? My 07.5 is doing the same thing, exhaust brake works when it wants to and I don't have any related DTCs.
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1995 RCLB 4x4: H-pump, 5x.012s, HX35
2001 RCLB 4x4: H-pump, 6x.013s, S472/S488
EdzGarage, Matt's Diesel Supply, HTS Transmissions