Tail lights head scratcher

truckblue · Mar 22, 2015

I'm having a problem with my tail/parking lights on my '08 Cascadia Straight truck. The brake and blinker lights work, but the tail lights only come on if I turn light switch "on" before I turn the ignition switch on. If I try to turn ignition on, then my lights, the parking lights wont come on. All the other lights work as they should. I recently had the ECM replaced. Not sure if there is a connection to that repair. Any thoughts?

tknight · Mar 23, 2015

sounds like a short in a marker light is tripping automatic breaker, had that recently, large bumps with a rubbing wire inside the box would trip breaker, loss of markers, got me pulled over, when i restarted truck they came back on, finished drive with 4 ways blasting into the night, fixed it in the morning when i could see it happening.

truckblue · Mar 23, 2015

tknight said:
sounds like a short in a marker light is tripping automatic breaker, had that recently, large bumps with a rubbing wire inside the box would trip breaker, loss of markers, got me pulled over, when i restarted truck they came back on, finished drive with 4 ways blasting into the night, fixed it in the morning when i could see it happening.

Thanks, TKnight. Not sure if that's the problem. My markers stay on, and once my tail lights come on, they don't go out. I might end up running a new wire from another source to my tail lights. It's not really a big problem, but I have to pull over and shut off ignition, turn lights on, then re start truck. Thanks again.

jamom123 · Mar 23, 2015

Have you had the AMU sensor checked? I know it can cause your brake lights to do all kinds of crazy things.

truckblue · Mar 24, 2015

jamom123 said:
Have you had the AMU sensor checked? I know it can cause your brake lights to do all kinds of crazy things.

No. What is it?

jamom123 · Mar 27, 2015

truckblue said:
No. What is it?

Sorry Truckblue for the delay in responding. The AMU sensor tells your lights to come on when the brake pedal is pressed. My AMU sensor went out and when I would barely press the brake the lights would come on, but if I put any pressure on the brake pedal they went off. It wouldn't hurt to have it checked they are usually located under the frame near the rear axle.

truckblue · Mar 29, 2015

jamom123 said:
Sorry Truckblue for the delay in responding. The AMU sensor tells your lights to come on when the brake pedal is pressed. My AMU sensor went out and when I would barely press the brake the lights would come on, but if I put any pressure on the brake pedal they went off. It wouldn't hurt to have it checked they are usually located under the frame near the rear axle.

ok, thanks.