Most of the time when the EUPs have active codes they need replaced. The EUPs are under the heat shields and supply fuel to the injectors. These codes can be active during warm up then go out, during normal driving or become active after the truck warms up. Either way they usually need replaced. 1 is at the front and 6 is in the rear.

The engine brake solenoid is the powerleash solenoid that is clipped on to the rockershafts and applies more oil for the power leash to activate. #1 is the front head and #2 is the rear head. The code should say which # it is. If it doesnt you could apply power straight to the terminal on the left side of the head below the valve cover with the engine off. You should hear it click. Whichever one doesnt click could have a broken wire or just needs replaced.

Thanks for the help. I looked into the EUPs a little today and all of them seem to b working ok. I checked the voltage to each EUP with a diode tester and found a good pulse on each EUP. I then cracked the injector lines coming out of the EUPs and found #2 & #4 not making a difference in the sound of the motor. I should have said from the beginning that at an idle I can hear a miss in the engine. So with that I am leaning towards an injector problem. Do you know if this is a big job on this engine. Is there any special tools needed to remove injectors?

The engine brake code I have not looked in to yet.

Bad injectors don't normally cause active EUP codes. Usually an active EUP code means a faulty EUP. Bad injectors cause a things like misses, smoke but not an active EUP code.

There is a injector puller that threads into the top of the injector and you turn a nut that pulls the injector out. If you dont have the tool you could use a bolt that threads into the injector top and popped it out with a prybar. The bolt size is 1/4 coarse or 5/16 coarse the length should be about 3-4". I cant remember which one it is but its that easy.

1-Remove injector line

2-Remove valve cover

3-Remove injector retaining nut. You will need a 5/8 allen head socket for this nut.

4-Screw bolt into injector and "pop" it out.

When you install the injector you will see a titty on the injector and a slot for that titty in the head. Screw the bolt you used to remove it back in and push the injector back in the bore while keeping the titty aligned with the slot. When you push it in you'll feel it seat in place, it will feel solid at the end of the push. Reinstall the retaining nut and torque to 45ftlbs. Reinstall all other parts.

Its easy, you can do it.

I wanted to check the fuel pressure so I interrupted the line going into the fuel rail with a gauge. Found pressure to be a bit low and also dropping intermittently. I have a feeling there was air in the system also because once I blead the system after I installed gauge the truck seemed to run better with no miss. After test driving truck with gauge still connected it ran better and light came back on, this time only with code for Eup #2 abnormal frequency.

Replace the EUP.

Just got the eup. I am going to replace it.