'94 Ram 5.9 gas. The factory CC worked one day, did not work the next. I searched this forum for ideas and then started following the trouble shooting recommendations I found. I really did not find anything wrong. However this is what I have done. Tested the switch in the steering wheel. Works as it should per electrical diagram in Haynes. It has power as it should and the fuse is not blown. The servo was probably original, so I replaced it and it has power from the brake switch as it should. I replaced the VSS and it has the power and reference voltage it should. I tested all vacuum components and lines including the reservoir and the check valve. The running engine generates plenty of vacuum (15+ inches). The servo holds vacuum under a static test as does the reservoir. I did continuity checks on all wires from the VSS, steering wheel switches and servo to the PCU, and checked for shorts on all. No shorts and continuity is solid on all wires. Still no CC. I have done these checks at least twice just to make sure.


I believe the only thing I have no checked, and don't think I can, is the PCU, although I would be surprised to find this one itty bitty part of it is out.


Oh yes, no codes.


Thanks for any advice.


FredJ

 

Check out the speed sensor on top of the rear axle. Some wires may have come lose.

 

Cruise on his truck doesn't care about the rear wheel speed sensor.

Does the speedometer work?

Does the little lite in the steering wheel come on when you press the button?

Do you get the correct OUTPUTS from the cruise control switches? All they do is modify the incoming voltage signal. PCM interprets from there. I think you can do a static test, with everything off, and just unplug the appropriate connector at the PCM, pushing buttons will change resistance across the pins.

 

^ after all that, then you have to eliminate the clock spring. If some things dont work, clock spring is done.

 

Horn works, speedo works. This model truck ('94) doesn't have a light indicating CC on. Their is 12 v coming into the switches and 12v going out to PCU. There is no circuit in the switches. The "Set" switch is normally "on" - pushing it creates an open in the 12 v to the PCU. The resume switch is normally "off" - pushing it creates a 12 circuit to the PCU.

 

Yep, your system is different than what I expected. If you don't already have it, grab the 95 service manual from here. It has troubleshooting flow charts for the cruise control.

 

Thanks VERY much for this reference.