red warning light?!

could be anything, you need to have the codes, i would not drive it that way.

 

If the master warning light is the only one to come on, maybe the 12V auxiliary battery is weak.

 

I might be having the same problem. I've got an '06 with 67,000 miles and in the last couple of weeks I've noticed the red triangle light comes on (most of the time) when I first start the car. It turns off in 3-4 seconds and the car drives normal, etc. It doesn't come on all of the time, but probably 80-90% of the time. I'm reluctant to take it to the dealer (they wanted a couple hundred just to change a light bulb). Does the red triangle indicate the car has through some codes? Would Autozone be able to read the codes?

 

Start simple: check the 12V battery. You can do this yourself, either with a voltmeter at the jump point under the hood or with the following no-tools selftest procedure (thanks to jdenenberg):

- Without brake pedal, press the Power button once and release to enter ACC mode
- Press and hold the MFD Info button while turning the headlights on and off three times to enter Maintenance mode; release Info button
- Press “Menu” (on screen)
- Press “Display Check”
- Press “Vehicle Signal Check” - the battery voltage is shown and should be about 12.4 to 12.8 Volts (normal for an unloaded battery)
- Again without brake pedal, press Power button and release to put a current load on the battery - the voltage should stay above 12.0V (if less than 12.0V the battery is not well, or there is a fault or unusual load somewhere)
- Press brake pedal and press Power button once to enter "Ready" mode - the battery is now charging at about 14V (if less than 13.6V or more than 14.4 there is a problem, possibly with the charging circuit)
- Turn car OFF to leave Maintenance mode

 

Last night I got a call from my wife, she was stranded because the Prius wouldn't start. The kids had been waiting for her in the car with the radio and headlights on. After about 20-30 minutes, the car wouldn't start. I jumped the battery and since then the red triangle hasn't come back on, so I'm guessing the problem was related to the 12V battery. I went through the Mnt mode procedure above and the voltage under load was 12-12.1V and in charging mode it was 14-14-4. I did turn the lights on and the voltage dropped to 11.6V, so they do really draw it down.

Thanks for telling me what to look for.

 

Good, a bad battery is a relatively cheap and easy problem to fix. Having been drained a couple times now it probably doesn't have much life left in it. The accessories will drain even a new one pretty fast.

 

Now that you know to get a new 12v battery, look at the deal from elearnaid on eBay. It includes all the required adapters (cable connectors and vent tubing) as well as a yellow-top Optima 51 battery (better than the the original).

JeffD

 

Especially with the headlight on, it goes fast; lots of power to the lights compared to a car radio.

 

Couldn't find the seller on ebay. elearnaid? Thanks

edit: found his website, http://www.elearnaid.com/12vo1topraub.html

 

Tell the kids to not do that. If you need to sit in the car using power, keep it powered up so that the engine can charge the battery as needed. The 12V battery in the Prius is pretty small.

Tom

 

Probably don't want to leave the "kids" in the car while it is READY - seems like a safety issue.

Nothing wrong with leaving the radio on for 30 minutes in ACC-ON mode (not IG-ON) assuming the 12V auxiliary battery is in reasonable condition; the problem was leaving the lights on which consume substantial power.

 

Silly me for missing the bigger problem here: leaving unattended kids in a car is always a bad idea. The questioner is lucky that a dead 12V battery was the only result.

 

Of course, his kids may be 23 years old... watch the assumptions, folks.