Q: I have a 2007 Toyota Prius. I was driving last night and the master warning light came on.

asked by on May 18, 2017

I was driving last night and suddenly the master warning light and check engine light came on. The car runs fine, I was able to get home. I drove it to the mechanic this morning and he said they scanned my car and the code is in the hybrid control module. He said he can't do anything and take it to the dealership. How serious is this?

My car has 98000 miles.
My car has an automatic transmission.

Hi There, The master warning light in the hybrids generally refers to the hybrid battery control module. This module monitors the charging of the high voltage battery (main hybrid battery) in these vehicles. When this control module is not working properly, this may cause the main battery to discharge rapidly as the control module will not know when to maintain, increase or decrease the charging of this battery, which may ultimately result in total failure of this battery. As you may know, these batteries are very expensive. This is something you should have looked at by a Toyota dealer immediately.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

What do the service codes displayed in the Maintenance Minder™ mean?
While your Maintenance Minder™ is primarily designed to let you know when it’s time for your next oil change, it also displays codes for other needed services based on vehicle mileage. There are several different codes that can be displayed,...
How do I adjust the height of the head restraints?
The correct height of the head restraints ensures comfort and proper positioning to prevent fatigue and strain on your neck and backs, which is especially important for long trips. The correct positioning is with the center of the head restraint...
Loud noise from underneath car.
Hearing any noise coming from your car can be startling, but it can be especially so when that noise is so loud others cannot hear you! Though the information provided is a bit limited, my experience tells me that the...
The front tire is making a knocking sound when I accelerate
The noise could be a from a tire that is separated or one of the front axles joints being bad. If you do not feel anything in the steering when the noise is happening, then the noise is most likely...
What's wrong when the alternator is not charging the battery, both parts are new, car Will go dead after driving 20 mins
Your vehicle has a fusible link in the wire harness that goes from the main wire on the alternator to the starter. If you had the starter replaced then maybe the wire was not put on the starter. The fusible...
Brake exhaust doesn't shut off when I press on the accelerator.
Hello and thanks for your question. When you press the accelerator to deactivate the jake brake system, the electronic throttle sends a signal to the computer to shut off the power to the jake brakes for acceleration. The switch inside...
My car has a coolant leak - 2001 Lincoln Town Car
The heater AC (air conditioning) case has a drain to let out condensation from the case. The heater core is positioned in the case that allows it get out through the case drain on the outside of the engine firewall...
I have 1988 oldsmobile cutlass ciera 2.8liter. I have had five mechanics check the car for a popping sound but they could not figure it out.
The popping sound from the engine sounds like the engine's timing is off or the fuel system is not delivering enough fuel to the engine. There could be a fuel injector (https://www.yourmechanic.com/services/fuel-injector-replacement) that maybe sticking and not spraying properly. The...
Press the gas and my rpm go up to 4000
Hi Sammi. Thanks for sending your question today. I'm not quite certain what issue you're having with the Cobalt. If you press the throttle and the car does not move, but the RPM goes to 4,000 RPM, then you likely...

Related articles

A Buyer’s Guide to the 2012 Toyota Sienna
The The 2012 Toyota Sienna is one of the most innovative and luxurious minivans on the market today. Not only has Toyota increased its size to better compete with the Dodge Grand Caravan and the Honda Odyssey, but you can...
A Buyer’s Guide to the 2012 Toyota FJ Cruiser
If If you’re looking for a hint of nostaligia in an SUV that can actually handle off-roading like a pro, the 2012 Toyota FJ Cruiser is the perfect choice for you. Designed specifically for tackling those off-road jaunts, what this...
The Best Used Cars to Buy If You’re a Painter
If If you’re a painter, and you work for someone else, chances are you don’t care all that much about what you drive, as long as it gets you to and from work reliably. On the other hand, if you...