Jake Brake Stage 2 Circuit Fail Open.

Question for you...did you have recent upper engine work done recently? Service injectors? Valve lash service? Etc...

1073/5--Jake Brake Stage 2 Circuit Failed Open

1. Disconnect the rear electrical harness connector of the two-piece fuel injector wiring harness.
2. Measure the resistance between pin 13 and 14 on the valve cover side of the rear two-piece fuel injector wiring harness . If you are using J-48671–10, measure across Jake Brake 2 pins.

1. If the resistance is between 9 and 12 ohms,Go to step 3.
2. If the resistance not between 9 and 12 ohms, go to step 5.
3. Turn ignition ON, engine OFF
4. Measure voltage at pin 14 of the MCM side and valve cover harness ground
5. Remove rocket cover
6. Disconnect the rear Jake Brake solenoid
7. Measure the resistance across the Jake Brake Solenoid
8. If resistance is between 9 and 11 ohms, replace the two-piece fuel injector wiring
9. If the resistance is NOT between 9 and 11 ohms, replace the Jake Brake solenoid

 

Let me get a picture for you of the location of this harness--it's not too bad.

 

The rear connector is the location I believe for the oil solenoid that controls the operation of the Jakes.

(Ignore the right side of the picture showing the mechanical fuel injector as yours is common rail)
Here's a picture showing the GENERAL operation...sorta.


Here's the location of the solenoid. It's located at the rear, hence the REAR rocker harness:


Here's a DL of a PDF that talks more about Jakes--if youre interested

http://www.jacobsvehiclesystems.com/files/media/Product/Sell_Sheet_DD_721_2.pdf

 

Most likely either an injector harness or solenoid. The harnesses are pretty britle and don't take much to break if they've never been changed.

 

@GameDayDog what dealer is this out of curiosity?

This really isn't TOO big of a deal. It's all upper engine work. At this point, I would suggest doing a valve lash job, and you'll need new rocker cover gaskets. Go ahead and change the solenoid with a new one--might as well in addition to the rear rocker wire harness. I'm not sure how many miles are on your truck--but I'd just take advantage of it. Maybe even consider getting new remanned injectors..? Engine brakes are very important--especially on hilly terrain.