I show Jake Brake Stage 2 Circuit Failed Open for SID 80 with an FMI 5. Could be wiring or a bad solenoid. Give a god lookover of the wiring from the head to the ECM, if all looks good there, the next step is under the valve cover. You can check the solenoid with an ohm meter. I don't know the spec, but it should be the same as stage 1 (that isn't setting a code). Also check the wiring under the valve cover. If the solenoid is open, there's your problem. If it's not, you have a wiring poblem to track down.