Unexplained Bangs...

[Mr. C]

I bought my Yaris hybrid T4 as a 2,500 mile demonstrator. It's now done 11,000 and had its first service. It's been everything we've wanted. But....

...once at, or about, 5,000 and again around 10,000 miles, I /we heard a large bang, seemingly from behind the front seats. I thought it electrical, since the stereo went off for a few seconds, before returning to normal. I enquired about the 'happenings' as I took it in for service, suggesting a possible fault from one of the cells which are under the rear seats. I was told later that 'a cell exploding would put a hole in the seat.' Must remember to put the mother-in-law there.

Anyone any ideas?

Thankyou.

[FROSTYBALLS]

Hello Roy - welcome to Toyota Owners Club. Moved to the Yaris club.

[Red Yaris 54]

And again moved....This time to the Hybrid section where you might just find out if something similar has occurred to another Hybrid owner........Let us know how you get on :)

[johalareewi]

A wild guess but JBL amplifier?

[Mr. C]

Is this something which is standard fit? No additional equipment fitted. Thanks for the thought.

[kithmo]

May be something has fallen off underneath, part of the undertray ?

As an aside, I doubt if exploding Battery cells would come through the seat as the design wouldn't be allowed under the construction and use regs. The Battery cells are encased in a metal shroud, which would prevent this.

[johalareewi]

Is this something which is standard fit? No additional equipment fitted. Thanks for the thought.

In the gen3 Prius, if the JBL option is fitted by Mr T, the amp is under the front seat. So if it goes pop, that is where you will hear the noise. You also mentioned the stereo going off for a few seconds.

On the other hand, you could have a loose 12v wire which occasionally shorts?

If you had an HV cell go faulty, the stereo wouldn't go off because that is powered by the 12v Battery.

On the other hand, there are posts about 12v Battery problems on new Aurises, so maybe your Yaris has a faulty 12v Battery too? Where is the 12v battery located in the Yaris?

[Yolina]

Where is the 12v battery located in the Yaris?

Under the rear seat, driver side

[jonesbach]

Electrical faults that make a loud bang usually leave enough damage that you will subsequently be aware of it.

12V Battery - If it was in the Battery you'd know about it(no battery). If the Battery was being overcharged it is just possible for a hydrogen explosion outside the battery in an enclosed space(the new Auris vents H₂ into a box section, is the Yaris the same?). I'd put this as unlikely as by now you would have needed a new battery(no electrolyte left).

Static discharge or fault on or near your stereo could well cause a 'thump' on the speaker and could subsequently temporarily affect the sound, I have something similar on an old TV I have. The question is, would it only affect one speaker.

[Mr. C]

Many thanks to everyone for your interest and imput. Kithmo: Nothing fallen off underneath; seems logical that both batteries would be encased to prevent damage to seat and passenger. Johalareewi: Amp might well be under the front (passenger) seat, but that is where the jack is. Loose 12v wire a possibility, but would have expected it to happen more than the twice it has. Jonesbach: Batteries both functioning correctly, although the Hybrid traction Battery has 20 modules: can I have lost a couple? Didn't sound like a speaker thump.