Ddec III cruise troubleshooting

###### thing has never worked. I would appreciate any insights you all have.

I have also hooked up a simple computer (blue fire) to read the computer status on these items.
1. Clutch switch verified ok and adjusted ok

2. Cruise will rev up engine when parking brake on or off

3. Brake switch appears to be tied to brake light switch? and it is ok and parking brake always shows as off

4. Pto switch verified ok

5. When i connect with blue fire system, it shows cruise switch on at ecu, with speed of 0 (when i’m sitting In the shop) and moving the switches around shows up in the ecu. The ecu registers speed when moving.

7. i have the wiring diagram for my vin, it is really basic, i can only see what pin number the cruise is on the ecu, but don’t know how to test that. There is a rumor of a better diagram for units with the modular fuse block, but I don’t have it

8. Had a bad ground on the ecu, fixed it

9. Throttle position sensor was throwing a code, it cleared up after disconnecting and reconnecting it. No open codes.

Engine is a 12.7 dd

Took it to a shop where they swore they could change settings in the computer. They couldn’t, but the tech advised he could see the max speed was set at 75 mph.

The cruise always shows “cruise active” as off, so is the cruise turned off in the computer settings? Is it possible to disable the cruise in the computer settings?

Thank you for any light you can shed on this.

 

1998 379
Old BJ blower truck

 

I just want to turn it on, if it is off.
Safety switches for clutch, brake, and dash on/off, set/resume work, as i can see their status change in the computer.

Only one speed sensor shows on the wiring diagram, but i will look on top of the trans for another.

 

Yes, thank you, i can see those two switches work correctly, and clutch switch works/is adjusted.

Speedo is steady also.

 

Thank you, interesting that you mention that, it looks like my parking brake is jumped out or the switch is not working. I will dig into that.