2003 Peterbilt 379 Cruise issues

ok im trying to understand exactly what you are trying to say. I have an 02 379. I can tell you this, the cruise control has absolutely no connection to the brakes. or at least in my truck. If i have cruise control set, tapping the brakes wont shut it off. Only the clutch will. So i cant see how its possible to set the cruise control by tapping the brakes. Even if it was connected to the cruise control it would not set the cruise but in fact do the opposite, disengage it.

 

Cam,

Your Cat should also kick out cruise with brake applied. I would say that the ECM is not seeing brake application signal correctly.

OP,

What engine are we working on? Has it always been this way? Sounds like maybe configuration settings screwed up in the ECM to me.

 

I have a 94 379, when my cruise was acting up and not working correctly, eventually I would get a sensor that would start leaking. That sensor would be behind or under the panel (however you see it). I don’t know exactly whether is was the brake or clutch sensor to knock it out of cruise control mode.

Btw, like just mentioned above, if my cruise was on and set, if I touched the brake, clutch or trailer brake valve, it would disengage the cruise every time.

 

good to know. It doesnt. When traffic slows and i go to hit brake, she keeps trucking.
Ill look into it next time im on a scanner. i appreciate the info

 

I been told, that sensor that deactivates the cruise, what some will do is bypass it. They would remove the sensor and stick a plug in the base.
Edit; what I mean by sensor, I think it’s more of a “Sending unit”.

 

well iam the second owner of the truck. I always scratch my head at some of the stuff the previous mechanic did when i work on my truck. so i can see that being possible

 

I had one shop tell me to plug it up cuz those sending units are cheaply made these days and they go out more often than before. But told me to beware that if I bypass it(plug it) I will have to deactivate the cruise manually always.

 

yeah thats how my truck is. Ive learned how to adapt to it. so it sounds like its a good thing for what the issues are

 

The cruise control should disengage either by applying the brakes or by pushing in the clutch.