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Ask Ted Ritter Your Own Question
Ted Ritter
Ted Ritter, Toyota Master Tech
Category: Toyota
Satisfied Customers: 4407
Experience:  Toyota Master Tech, ASE Certified
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Master warning light, brake warning light, check engine

Customer Question

Master warning light, brake warning light, check engine light, and hybrid system warning light.
JA: Does the light stay on, or does it blink?
Customer: All stay on.
JA: What is the model/year of your Toyota?
Customer: 2007 prius
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Tightened gas cap. Stopped and restarted vehicle. Left vehicle off for long periods of time.
JA: Anything else you think the mechanic should know?
Customer: At one point, electric motor would not charge battery. Turned vehicle off and on. Charging returned. Acceleration feels a little sluggish.
Submitted: 1 year ago.
Category: Toyota
Expert:  Ted Ritter replied 1 year ago.

Thanks for posting

The first thing to always check when a Prius exhibits some warning lights is to check the 12 volt auxiliary battery in the trunk, unless it was replaced recently and is known to be good, this battery controls the voltage for most of the hybrid computers, it must show more than 11.8 volts if less either charge or replace it, in most cases it will not accept a re charge if more than four years old.

You mentioned the check engine light was on, this indicates that the engine control computer has detected a fault with it's control system or there is a communication malfunction between the hybrid and engine computers.

The check engine light on will also trigger hybrid codes so the first thing I would recommend to you is to get the engine codes from the computer, most of the larger autoparts chain stores can help you do this or get the trouble codes for you at no charge (expt CA), After you have the check engine light diagnosed and have some code number information I can help to figure out what should be done and how to proceed, In most cases once the check engine light problem is fixed the other lights will turn off and return operation to normal.

Customer: replied 1 year ago.
I will check these things. But I am noticing that the acceleration problem is getting significant, and that (according to the interactive screen) the electric motor seems to be operating erratically. It does not always charge the battery the way it should, and power is not coming from the battery at some times when it is needed (like accelerating out of a stop at an intersection). I'm guessing that this is highly significant.
Expert:  Ted Ritter replied 1 year ago.

It all depends on what the diagnostic codes indicate, that's the starting point and don't forget to check the 12 volt battery. If in doubt replace it.

Customer: replied 1 year ago.
Have not checked 12v yet, but diagnostic code was: no code recorded for this alert.
Expert:  Ted Ritter replied 1 year ago.

Ok, let me know about the battery.

Customer: replied 12 months ago.
12v battery is fine.
Expert:  Ted Ritter replied 12 months ago.

Ok, then we need to look a little deeper, those lights that you mentioned earlier come on for a reason and there are trouble codes in one or more computers, I would recommend that you have it scanned for codes with a diagnostic scasnner that is capable of accessing the hybrid system computer as well as the engine control computer.