Tail Light Won't Turn Off

How strange. The Electrical Wiring Diagram for the Prius Prime (EM32D0U, available by subscription to techinfo.toyota.com) shows that the tail lights are switched by a TAIL relay in the Instrument Panel Junction Block Assembly; when the relay is open, there shouldn’t be any voltage applied to the circuit. I don’t see any provision for dimming at all.

The load side of the TAIL relay is connected to selected front and rear exterior lights (but not to the stop lights) and to numerous devices for instrument panel illumination. Perhaps the tail lights are being back fed somehow, or there is a fault in the wiring.

If the car is under warranty and you can reproduce the problem, I’d suggest taking it to a dealer for diagnosis—you might be able to find the problem using a multimeter, the EWD, and some troubleshooting skills, but this won’t fix it, and if you were to break a wire or damage a connector, it could be an expensive repair.

 

Should be under warranty.

 

Seems like that happens a lot at those tinting places. I guess one should request they listen to their own radio while working.

 

Hours of the car sitting with doors and trunk open with interior lights on. The small 12v auxiliary battery in the Prius is easily discharged under those conditions.

Posted via the PriusChat mobile app.

 

That reminds me. I forgot to re-enable the dome light on my wife's car after replacing her hatch push button. Oops!!

 

Glad a read your post. I had my windows tinted today and the same thing occurred on my PP2020 tonight. Hoping it will resolve by itself!

 

I had the same problems after getting my tires changed at Costco. Taillights won't turn off, causes the batteries to drain and check hybrid system alarm. I took it to the dealership. Paid 780 for diagnosis only. They wanted me to pay 4000 for parts and 3000 for 30 hours of labor. The problem was some corrosion in the junction connector by the passenger side to the main electrical harness. There's an easy way to fix it. Buy some gasoline, disposal electrical toothbrush, and a cup big enough to fit the center connector with the black tab. FIRST UNPLUG THE ORANGE SAFETY PLUG ON HYBRID BATTERIES AND UNPLUG THE MAIN 12 VOLT BATTERY. there's a live wire connected to the harness. Then remove the cover by the front passenger side by unscrewing the plastic knob located in the back of the side panel then pull it off to expose the main electrical junction box. At the very center there's the connector with a black tab that locks the connector into place. You will need a flat screwdriver to unlock the locking mechanism by pushing it down. Then pull the black tab out and up as it will arc and rotate out and up. Poor gasoline into the cup and dip the connector into the cup to dissolve the corrosion. Turn on the toothbrush and place it in the cup to agitate the gasoline and connector for ten minutes. Then use the toothbrush to clean the hole where the pins go into. Make sure all the corrosion color blue is remove. VERY IMPORTANT. MAKE SURE EVERYTHING IS DRY BEFORE YOU REPLUG. I used a blow-dryer to speed up the process. Then replug the connector back by placing the connector into place and push down and in on the black tab. It will click if you put it back in place correctly. Then replug the 12 VOLT BATTERY and the orange safety clip. DON'T FORGET TO SIDE TO THE RIGHT TO ENGAGED THE SWITCH. Good luck