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2006 Toyota Prius electrical problem - please help!

I bought a 2006 Prius used years ago. From the start I had an intermittent electrical problem.

Here’s how it goes:

  1. I drive the car.
  2. I park the car and go about my business.
  3. I come back to the car, get in, push the brake and hit the start button.
  4. The interior light is an orange (rather than yellow when at full charge); the car ‘starts’ except the radio does not come on and the “P” in the shift icons is not highlighted - and the car will not shift into gear.
  5. I turn the car off (can’t push the brake, or it doesn’t turn off properly).
  6. I jump the car (from another car or portable battery). Everything works as desired. Until the next time.

Other notes:
–This usually happens when I’m in a hurry or the weather is crappy. That might just be my perception. . .
–I’m asking about this now because the repeated stress on the battery plus cold weather seems to have resulted in a dead 12V. . .I expect I need to replace it, but I wanted to see if you guys might know root cause or how to troubleshoot the ‘car not starting, electrical short?’ problem.
–I’ve taken the car to multiple dealerships - everyone says “well, everything looks fine!”. . .
–(maybe, maybe not related) the headlights will sometimes go out while I’m driving. Used to only happen to the driver’s side, now happens to both although not simultaneously (I need new bulbs?).

I love the gas mileage, but I’m really getting done with the car and this issue.

Any suggestions, similar experience or thoughts are greatly welcome!


How old is the 12V battery? That’s my first guess as to the problem.

Have you looked around the priuschat forum?

I’d start with a new 12v battery. Because it is a Prius, there aren’t many people here qualified to handle many questions about them specifically, but there are some here that are familiar with Toyota’s in general and sometimes that helps.

As a general answer, if I remember correctly, the daylight running lights are controlled by the body control module (BCM), which means all the headlight functions run through this computer. Some of the other functions you are having problems with also use the BCM. Computers do not like batteries with low voltage, they sometimes don’t boot right, or something like that. They also don’t like it when the battery terminals get a little dirty or oxidized.

Replacing the battery and cleaning the terminals might solve your problem. You might also make sure the body to engine grounds are all good, these are little braided straps you will find going from various points on the engine to the body.

Good luck.

January 19, 2009, Toyota Issued A TSB (Technical Service Bulletin) For 2006 - 2009 Corolla, Highlander, Matrix, Prius, RAV4, And Sienna Vehicles For Their Technicians.

“Some customers may experience multiple warning lights illuminated, vehicle not shifting from Park to Drive, and other accessories becoming inoperative after the vehicle has cold soaked in sub freezing (below 14F[-10C]) ambient air temperatures. A newly designed relay has been made available to improve this condition. Use the following procedure to address this concern.”

This looks like a possibility, although I don’t see anything about headlights cutting out. Your vehicle may not have been this cold soaked, but is it possible that this same relay is to blame if this description matches your symptoms ?

I’d be tempted to pull this IG1 ignition relay, heat it in my hand, tap it, and replace it the next time it throws a tantrum.

If interested, search for or obtain a copy of T-SB-0047-09 or a newer revision for details.


I think I have the solution. I would leave my Prius at the airport for two days and it would be dead when I returned. If I left it in my garage for two days it would be dead. How improbable is it that a battery rich car could die so often? I was a big hit with the roadside assistant guys.

After a lot of gnashing of teeth and several years of poor answers from the car dealer - they finally got it right. There was a small electrical leak in my radio. original cost to repair - over $900. due to the magic of modern engineering, you cannot just fix the radio - you need to replace it. (Or is it the magic of modern merchandising?)I declined repair and kept calling my new best friends at roadside assistance. The next dealer visit - well they could do it for over $400 - It turns out that they were quoting me for the radio and the telescreen - and you could just get the radio. I finally agreed, and now I have no problems. Best of luck.

A 12 volt battery lasting more than 3 years is an unexpected bonus. But you can put a cheap 12 v test light in series with the battery to see if any current is being drawn when everything is turned off. If the light does not light, you may be safe. But you can also use an ammeter, which is much more sensitive than the test light. A few milliamps for clocks etc would be a normal OFF current draw. And, as Keith says, check all connections, especially grounds.

A 12 volt battery lasting more than 3 years is an unexpected bonus.

You must live in warm climate… While 3 years is considered long in warmer climates…7-10 years is the norm in the northern climates. Heat is a real battery killer.

I have a 2007 and there is a recall for the headlight problem. Both lights would go of while driving. It is not repaired and no more problems.

I would replace the 12 volt battery, 6 years was a good life.

If you have HID headlights, this is a known issue.|76&Model=Prius|1026&Year=2006|2006&carId=005&n=15684181&newCar=1&s=automotive&vehicleType=automotive Buy two Search youtube for hints on installation, it is not obvious.