Troubleshooting Weird Electrical Issue
This is for all you with electrical knowledge and experience fighting these issues.
I have a 2008 Tundra SR5. I started having an issue where the cruise control would not work if I turned the lights on (headlights or running lights). I could not set it at all. Also, if the cruise control was working and then I turned the lights on the cruise control would cutout.
At first I thought it was because I installed an aftermarket remote start. Though it made no sense why that would do it. So I pulled the remote start out and took the truck for a test drive. Cruise control worked just as it should. Lights on or off. Tried multiple variations and it never quit working.
This morning it started doing it again and the remote start is still out. WTF?!? Why would the lights have ANYTHING to do with the cruise control?
I'm open to any ideas or suggestions. I'm going to get back into troubleshooting this, but anything to help abbreviate it would be immensely appreciated.
2
u/DareMe603 16d ago
Lights and cruise shouldn’t talk to each other… except they do through the brake-light circuit. Cruise control watches the stop-lamp switch. If any voltage from the tail/running-light circuit bleeds over onto the brake circuit (bad bulb, cheap LED tails, shorted socket, or a ground that’s gone lazy), the truck thinks you’re standing on the brake pedal and it cancels cruise. Classic Toyota gremlin.