07 Prius Dead - Any Guesses?

The red triangle of death (engine warning light) showed up. I drove directly to the dealer. The dealer fiddled around for a week. I received telephone calls about what kind of gasoline, etc (clearly the dealer did not have a clue). Toyota engineers were finally called in. Problem solved: a single loose connection on the engine.

 

It is highly likely that you need a new 12V auxiliary battery. The reason that the gas gauge is blinking one bar is because when 12V power is lost, the gas gauge loses its fuel level memory. It will take a few minutes to restore the correct reading.

For future reference: when the car became READY after the jumpstart, you could have driven it, if the amber check engine light was the only warning light lit. Further, if the 12V battery is in good condition but just had a low charge, you could recharge it by leaving the car READY for several hours.

 

The check engine light comes on when the engine ECU logs a DTC. I normally would not expect that light to appear due to a weak 12V battery. However, it's possible that given the low voltage on the 12V bus, that a spurious error was logged that will go away after you disconnect the old battery (thus cutting power to the ECUs) and install the new one. Once you install the new battery, then you can see whether the check engine light persists, in which case you will have a second problem to solve.

I'd encourage you to DIY install the new battery. It's not quite as simple as you suggest in your msg above, however.

You'll have to remove the traction battery vent that runs over the 12V battery, and also move the brake power supply located next to the 12V battery. You can remove the hardware that secures the brake power supply, without removing the wiring harness connector. There's enough cable slack so that you can move the power supply an inch or so away from the battery.

Pay attention to the various nuts and bolts as you remove them, so that you can put the correct hardware back in the correct locations.

Then you'll have enough clearance to remove the terminal connections, battery bracket, and vent hose (suggest you remove the negative cable where it attaches to the body, rather than where it attaches to the battery) so that you can lift the battery out of the hatch area.

Some owners get stumped by the red plastic terminal cover, trying to remove it from the fuse block. Just bend the cover up sufficiently so that you can access the nut securing the positive terminal.

The fuse block will be attached to the battery bracket with a plastic clip. Rather than try to remove the fuse block from the battery bracket, just remove the whole assembly as one part.

The battery vent runs into a rubber grommet located on the body, to vent hydrogen gas to the exterior. You can feel around with your left hand to locate that grommet in the body, if the vent hose pops free before you have a chance to see where the hose leads.

Once the old battery is out, transfer the vent hose and the negative cable to the new battery, then reinstall. Make sure all electrical connections are tight, and that the bracket is snug (but not so tight that you risk cracking the battery case.)

You'll need to reset the driver's window auto up/down function once power is restored. Make the window halfway open. Then close the window, and continue to hold the window button in the upwards position for a couple of seconds after the window is closed. Then the auto function should work. You'll probably have to reset your radio presets and you will lose trip odometer and possibly MFD mpg readings. You will also note your fuel gauge blinking one bar for a while, until that system figures out how much fuel is in the tank.

Hopefully this provides enough guidance for you to be successful without spending lots of time on this project. Good luck.

 

+1 on the DIY. Once you get the floor out of the way and look at it for a few minutes you'll see how easy it really is.

- D

 

I don't know whats wrong with your Prius, but Jim Lentz just came on Television and he say's he's sorry and suggests you call the 1-800 number...

 

Thanks for the update; is your check engine light gone now?

Your story illustrates why I believe it is a waste of time & money to pay for a dealer (or anyone else) to do a load test on the 12V battery. Too often you'll get a good health report, only to find that you have to replace the battery anyway. It makes much more sense to spend the $95 on partially funding the purchase of a new battery.

I doubt that there's anything wrong with the Prius charging system. To verify this, all you have to do is to hook your digital multimeter (which I assume you own since you mentioned the voltage of your new battery and failed battery) across the battery terminals when the Prius is READY. If you measure ~13.8VDC then all is well.