What a pain in the ass!
A while back I’d noticed the cruise wasn’t working and put it on the TODO list. Since I’m planning a couple longer trips in it, I figured today was the day to work on it.
First thing to check was the vacuum hoses. Sitting in the engine bay, they’re know for perishing and causing the system not to work. Sadly, mine were in good shape.
Assuming then that the vacuum pump sucked in a bunch of crap the last time the hoses were bad, I went ahead and swapped over the pump for one I had hanging around. I also hooked a manual vacuum pump up to the throttle actuator and proved that it was working.
Actuator was working and swapping the pump made no difference.
Ok well I guess it could be my brake switch? But my brake lights are working fine. In fact I just replaced them with LED bulbs a couple weeks ago.
Well must be the Cruise ECU? The manual shows that on the driver’s side so I’ll just pop off that panel....
Oh. The other driver’s side.
Take off the glove box, remove the panel, and pull off the ecu and swap it with a junk yard spare.
I can hear the relay clicking, but no actuation.
Uhh... ok. Wiring harness maybe? Or...
It couldn’t be...
Not my LED tail lights?
I pulled the 3rd brake light and replaced it with conventional and...
Yup. Everything works fine now.
Uuuuuuuuuuuuuugh I guess the system uses the resistance of the tail lights as some sort of pull down or load resistor. Without it, the system assumes the brake pedal is pressed and shuts off.
Now I have an completely torn apart interior but working cruise! Crap...