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Ask Ted Ritter Your Own Question
Ted Ritter
Ted Ritter, Toyota Master Tech
Category: Toyota
Satisfied Customers: 4283
Experience:  Toyota Master Tech, ASE Certified
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My son has a 09 prius the auxiliary battery died, and we

Customer Question

My son has a 09 prius the auxiliary battery died, and we changed it, however the check engine light came on, and the car won't start, I'm confused what should I do?
JA: Does the light stay on, or does it blink?
Customer: It stays on
JA: Are you fixing your Prius yourself? What have you tried so far?
Customer: Yes. Next I'm going to check the codes
JA: Anything else you want the mechanic to know before I connect you?
Customer: I did jump start it, and stayed on until I disconnected the cables, and then it shut off
Submitted: 6 months ago.
Category: Toyota
Expert:  Ted Ritter replied 6 months ago.

Thanks for posting

Since it starts and runs with the jumper battery it seems the battery you put in is not fully charged, do you have a battery charger? If so please charge the 12 volt battery at about 10 amps for 5 hours and check again,. The Prius batteries charge very slowly so it takes quite a while because the is no alternator like in non hynbrid cars. It would also help if you have a voltmeter to check the battery voltage, it must be at least 11.5 volts for the computer to let the car run.

Customer: replied 6 months ago.
I only was able to start it once, and after that it hasn't started since
Customer: replied 6 months ago.
I bought a new battery, and still nothing, but the check engine light
Expert:  Ted Ritter replied 6 months ago.

Even with a jumper battery it won't start? Do the lights on the dash turn on and do you get a "READY" light?

Customer: replied 6 months ago.
Nothing
Expert:  Ted Ritter replied 6 months ago.

Somehow it's losing voltage from the 12 volt battery to the front fuse box, do you have a volt meter? Check to make sure the ground wire on the battery is connected to the body.

Customer: replied 6 months ago.
Could it be a code that needs to be reset?
Expert:  Ted Ritter replied 6 months ago.

At this time I don't know if there are any codes, you'll need to check but if no lights on the dash turn on with the power button it won't show any codes, we need to find out why there is no power to the dash, I would like to verify that the system has enough voltage to even power up, can you get a voltmeter and I will instruct you what to do, otherwise I can't help anymore and you will have to have it towed to a dealer.

Customer: replied 6 months ago.
I will
Expert:  Ted Ritter replied 6 months ago.

Ok, let me know if you need anything else or have other questions,.

Customer: replied 6 months ago.
Thanks
Expert:  Ted Ritter replied 6 months ago.

You're very welcome.

Customer: replied 6 months ago.
Hello Ted I've got the voltage meter, what's next?
Expert:  Ted Ritter replied 6 months ago.

Next open the fuse box under the hood and then open the red cap with a plus sign on it, measure voltage there, let me know what you get.

Customer: replied 6 months ago.
9.06
Expert:  Ted Ritter replied 6 months ago.

There is the problem, 11.8 is the absolute minimum or the hybrid system will not start the engine, you'll need to charge the battery up for about 5 to 6 hours at a low current of about 10 amps. Or you can take the battery where you bought it and see what they will do, these batteries are not the same as regular car batteries as I said earlier.

Customer: replied 6 months ago.
After charging volt meter reads 12.5, but still nothing
Expert:  Ted Ritter replied 6 months ago.

Check the ground connection on the 12 volt battery make sure the ground cable is attached to the inside of the fender.