Factory Jake Brake issues- currently on the road with a 5th wheel

[scootergmc]

Hello everyone...

We're out exploring flyover America with my father in law's '06 and 5th wheel trailer.... everything is going fine, except the jake brake. It's an '06 auto w/ the OEM/mopar jake brake installed at the time of purchase (not factory). While on the road through Nevada I noticed it wasn't working. The light on the switch wasn't working either. I didn't have time to work on it until I got to North Dakota. The pump is producing vacuum. The 10a constant hot fuse is all good too. With my limited tools, I found power at the relay, jumped it, and the solenoid functioned as it should. I checked all grounds, and have constant hot to the relay. The Napa in Beulah, ND had a relay, so I bought one to eliminate that issue if it was. It wasn't. No change. I checked the two wires that go into the ECM on the engine, they weren't protruding or anything, and I don't think they're the problem since when I pull the switch (on), it changes the lockup of the transmission. I think I'm now left with a bad switch, and I don't know how to check that. I have basic hand tools with me.... It's not a big deal as the 5er is only 26' and pulls easily, even cresting the continental divide a few times, but I'd like to be able to isolate the problem best I can, since it's not my truck and I'd like to return it in the condition in which it was provided.

Forgive my convoluted typing as I sit here in Custer, SD at the RV park, 22 ounces into a frosty cold IPA- I'm a lightweight... Thanks in advance.

 

[Ozymandias]

Did you check for codes? There are two special codes for the functionality of the Jacobs Brake.
And did you check all the groundwires?

The brake works that way that with the switch you tell to the ecm that you want the brake, and then the ecm switches actually the relay.
So if you want to check that by yourself you need to have a controlwire to the relay, with a small bulb, that you can see by yourself while you were driving if the ecm at least try to switch the relay.

 

[Ozymandias]

http://www.jacobsvehiclesystems.com/files/support/docs-pdfs/32414 E2_Screen.pdf

 

[Bob4x4]

The most common failure I have run into other than the switch and vacuum pump that you have verified is the solenoid failure.

 

[p-Bar]

I't sounds to me your not getting the signal from the ECU . I would just hotwire it manually operate it the cab till you can get it figured out . It all was BS that the torque converter had to be locked up .

 

[scootergmc]

Thanks guys.

I had no codes. I ended up chasing all the wires and found the black wire had come loose from the green/black/yellow junction. I have the switch back. So all that was left was the pump. I pulled both ends from the solenoid and held them together and the brake failed to actuate. So the pump is bad. Looks like I'll be replacing that when I get home. Kind of odd that two things went wrong at the same time, but Murphy's law is what it is. Thanks again for the help.