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

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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.

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