Engine/Transmission (1998.5 - 2002) Jake Brake Question

[benhall]

I'm having an issue with my Jake Brake not working after long periods of driving with the cruise on and at interstate speeds. Is there something in the ECM that is telling the actuator not to work? It will start working again after I shut the truck down for 5 min. , so I'm not sure what's going on here.



Ben

 

[WestTN]

The ECM activates the brake when the accelerator is released. Maybe your APPS is slightly misadjusted.

 

[blacksheepdiesel]

Never heard of this problem before. Assuming all electrical connections are good (they are, right?) I would suspect either the ECM or the APPS. Any codes? If the APPS is beginning to fail it could send the wrong signal to the ECM which would not allow the brake to work.

Godspeed,
Trent

 

[benhall]

All of the connections are good. The APPS was just replaced in March, so it should be good. Could the SMARTY have anything to do with it?

Ben

 

[blacksheepdiesel]

Might try putting the stock software in and drive it for a little bit ( I know, it SUCKS!). Then put the Smarty software in and see what happens. Process of elimination.

Godspeed,
Trent

 

[ToolManTimTaylor]

Wow even on a 6Spd truck you still have to use the ECM? My BD is straight up on a micro switch under the pedal so when you are off throtle I simply flip the pedal up. ( I set it that way)

 

[PC12Driver]

If it's been on for a while, I'd suspect that the valve is mechanically sticking after it gets heat soaked. Especially since it will work again after the truck cools off. I started experiencing that with mine just before I took it off. It would stick, and a couple of taps on the actuator (engine idleing, brake on) would free it up.



Unfortunately, I don't have a fix for you. I changed turbos shortly after the problems started and never went any further with it.

 

[icman95]

I was going to suggest the same thing as PC12Driver. I have the Jake in my truck and have never had a problem, but we have Pacbrakes at work and have similar problems. Our mechanics tell me that they will work normally after cooling off a bit, but that is a symtom of a bigger problem. In the Pacbrake case, per the factory, there was a bad batch of castings made without enough nickel and this is what is causing the problem. They take them apart, clean them out and lube them up. Seems to help for a while.



I've never heard of it on the Jacobs, but the symtoms you describe, barring any electrical problems are surprisingly similar.

 

[blacksheepdiesel]

TTMT,

Yep, ECM controls the e-brake on-off. The e-brake could be used with a throttle switch like yours, the ECM does not have to be in the loop. The e-brake manufacturers' took advantage of the ECM control because there are less parts to install which makes them more $$.

Godspeed,
Trent

 

[benhall]

Thanks for the input. I will see if I can get the truck warm enough to do this again while I'm home on leave to try out the tapping on the actuator to see if that does anything. Is there any way to lube these while they are on the truck?

 

[ToolManTimTaylor]

TTMT,



Yep, ECM controls the e-brake on-off.

Hey Trent, The same applies in this case being his is an H. O? (Which in 02 is a manual trans) I guess I never really understood what the controller (or exh brake module) is looking for. Sure would be nice for him to get an E-Shifter and convert it so he can use the brake when he wants rather than the ecm.



Kinda like

https://www.turbodieselregister.com...ns/158982-e-brake-switch-gear-shift-knob.html

 

[PC12Driver]

TMTT, I think you're giving the ECM on the second gens too much credit for how much control it has over the ex-brake. Basically there's a pin in the 50-wire bundle that supplies 12v after 2. 5 seconds of throttle-at-idle. There's no warmup function or slow speed cutout. You just take the send from that, run it through your favorite switch, and then to the vacuum switch for the ex-brake. I think that's pretty much how all the 2nd gen 24v ECMs worked, auto or manual.



With the delay, you can leave the switch on and still shift gears without the brake cycling every time you let off the throttle.

 

[HBarlow]

I'm having an issue with my Jake Brake not working after long periods of driving with the cruise on and at interstate speeds. Is there something in the ECM that is telling the actuator not to work? It will start working again after I shut the truck down for 5 min. , so I'm not sure what's going on here.

Ben

I had exactly the same symptom when my '01 HO6 speed was young and had only 60k miles on the odometer.

It was caused by a problem with the APPS. I was told that the original APPS modules installed in some '01s had a compatibility problem with the Jake Brake equipped trucks. I don't remember the details off the top of my head now, years later, but the problem was due to the APPS not allowing a zero volts (closed throttle or zero fueling) signal to the ECM when cruise control was turned on but disengaged so the ECM would not allow the exhaust brake to engage.

I replaced the APPS and the problem was cured and never returned.

 

[blacksheepdiesel]

TMTT,

Yeah, I do have the gear knob switch for my e-brake, like it a lot! I still have the rocker switch that comes with the Jacobs so I can turn the e-brake off if I let someone else drive the truck, but that rarely ever happens!

Godspeed,
Trent

 

[benhall]

If this is an APPS issue, which it is looking like, is there a way I can adjust it to make it read zero? I do have my old APPS with the Williams replacement sensor for when the current one fails.

 

[HBarlow]

I was communicating with a Cummins/Jacobs product engineer at the time who told me that my problem was caused by the APPS. Neither he, STAR, or a trained Dodge dealer tech thought the APPS could be adjusted to cure the problem.

 

[blacksheepdiesel]

The APPS idle validation switch (which is all of the circuit board in the APPS) is what fails most often. Go ahead and put your replacement on and see if that fixes the problem.

Godspeed,
Trent

 

[OldRetiredAFGuy]

My OEM brake did this on my 2002 3500. The Dodge house mechanic and I finally figured out that it was carbon build-up, apparently from lack of use. Try turning it on when you start up the truck, and then keep it on, constantly cycling it every time you think of it while driving.

Mike

 

[PC12Driver]

Seems like a key clue that's getting overlooked here is that it only happens when the brake is heat soaked. That pretty much points to the mechanicals of the brake. If it was the APPS, he'd have issues all the time.



Since you have a spare APPS (btw, the Williams version works great - just plug in and adjust the bellcrank stop to remove some of the deadband) it won't hurt to change it, but I wouldn't expect much.

 

[benhall]

I didn't think replacing the APPS would help, since the signal is getting out from it.

I did find a coolant leak from the return line from the heater core where the rubber hose and the hard line meet. Could leaking coolant have an affect on the vacuum canister that operates the butterfly?