Electrical system and CD

I have a '05 Prius. The CD stopped working an month ago. The disk would go in, it would try to read it, fail, and spit the disk back out every time. I took the Prius in for periodic inspection/maintenance. They replaced a blown left tail light and ordered a replacement unit for the CD unit. When I got the car home, I noticed that the CD was working although nothing had been done to the CD player. On a hunch, I took out the left tail-light bulb – the CD failed. Putting the bulb back in restored the CD function. I repeated the test several times with consistent results. I will defer replacing the CD unit indefinitely. I wonder how many Toyota customers have replaced CD units (at $265 a pop) because of an open tail-light circuit. Have you heard anything like this before?

For $265 you could get a better stereo than the factory unit

What you describe is pretty strange. I can only think that the bulb is making a ground connection somehow that allows the player to work normally.

Yea, it sounds like the CD unit has a bad ground and is somehow finding a ground through the lamp.

That is a weird one. That’s the problem with enormously complicated vehicles like this—you get weird unpredictable interactions that are very difficult to track down. It could be that you’re getting some weird electrical interference through the wire that tells the stereo to dim its lights when the headlights are on, and with the bulb in the circuit it’s being filtered. Or the computer in the stereo may be encountering a condition that its software was never debugged for.

If it was Microsoft, they’d probably tell you that the CD not working was a feature to tell you to replace your burnt out taillight. It might be worth posting this one on a Prius forum–you might save some people a lot of hassle.

On a side note, $265 is pretty cheap for a stereo from a dealer.