"Check Hybrid System" Warning Screen

Hi guys! First time poster...

So I was working on installing a custom stereo system in my new Prius C. I had the main 12V battery removed for awhile. I put everything back together and now I get an error screen when I go to start the vehicle:

CHECK HYBRID SYSTEM
STOP THE VEHICLE IN A
SAFE PLACE IMMEDIATELY

Vehicle will not go into ready mode and is undriveable but all electronics turn on and work. Some research on the limited amount of Prius C information so far has shown that disconnecting the 12V battery may cause this screen to show up. Also that some installers have bumped into the orange connector on the hybrid battery and this will also cause the error screen to show up. Here is what I have tried so far:

+Cycled ignition on and off multiple times (I believe they said it was 3 times for original Prius would clear this screen, no luck)
+Checked voltage on 12V battery: measures 12.3VDC under load (vehicle in start mode) and also not under load (vehicle off)
+Checked that orange plug on hybrid battery is properly inserted
+Checked for Check Engine Light (CEL) codes, none
+Checked in the factory owners manual (said call Toyota dealer immediately, no further details)
+Called Toyota dealer, said they don't know and to tow it in (no help)

I should also mention the entire interior has been removed. I made sure all essential plugs are back in, only thing not connected is the passenger seat and light for the trunk (shouldn't impact driveability as I drove it like this before no problem). Problem showed up after I disconnected the 12V battery.

I suspect there is a reset procedure to get it out of this lockdown mode but I can not find it listed anywhere nor does anyone I've talked to knows what it is. Either this or 2. I blew something up or 3. Something is still disconnected somewhere despite my searching.

Any help (besides telling me to take it to the dealer) would be greatly appreciated. Thanks!

12.3 under load for the battery is a little low... Maybe charge your battery a bit? Also does this problem occur when your new stereo isn't drawing power/isn't connected? I've read on here about people having problems with the MFD after installing aftermarket stereos because the stock stereo is sending specific signals to the MFD that need to be bypassed by 1) adding a specific resistor to a specific wire, or 2) keeping the stock stereo connected and stashing it under the seat. Hope some of this helps...

I was thinking about a lighter battery so if I swap mine out this will also occur? Strange because what if people need to change the 12v battery when it goes bad?

Lighter battery? It's really small and light already... Going smaller is going to make the car more likely to not work properly... But as for replacing a 12 volt, it's no big deal other than maybe having to cycling your car on and off a few times to get everything running again... You also have to reset your clock and radio preferences as well (at least on '07 Prius) and you have to hold passenger side window button all the way up and all the way down to get it to run in automatic with just one push again.

Ok I left the battery on a trickle charger for 4 hours and now the battery measures 13.15 VDC. Warning light still shows up. I even tried just for fun disconnecting the battery for awhile to reset and reconnecting, still no luck.

I don't have any fancy stereo equipment hooked up (yet) besides just the new head unit. I'm not sure that the MFD would be an issue since I got the Prius C Two which does not come with factory navigation. Also the aftermarket head unit was installed in this car for about a month prior to this incident so I would think if it was a problem that it would have shown up then. But I'm willing to try anything at this point.

Well, I guess if you haven't tried putting the old stereo back in to see if that gets it running? If that solves the problem you'll probably be able to track down a solution from your car stereo manufacturer or a reputable installer who's already worked on Prius C.

I would disconnect radio first and if that didt help check fuses.

They make Li-Ion or Dry Cell batteries that have the same capacity but are lighter. Just a nut about further improving things like weight or handling when I can.

How can I learn more about who makes these batteries? Do They make both HV and 12v batteries? Maybe you have some links?

Often times people remove the high voltage interlock and do not install it correctly causing Prii not to ready. I have not come across a Prius c interlock yet but if it were a Gen II I would tell you to make sure to slide the lever after flipping it back.

Here is one for dry cell

ODYSSEY Batteries - Official Manufacturer's Site

Here are Li-ion

Flux Power · 12V Battery


A123 Systems Lithium Ion Battery Manufacturer | Lithium Iron Phosphate


12 Volt Lithium Battery - Products

There are more out there coming to market so its only going to get better.

Update: I put the factory radio back in, still giving warning message. I will try checking fuses.

Here are some pictures of the high voltage interlock. I am pretty certain it is installed correctly...

Looks like you need to slide the lever up.

I agree with Avi's.

This is a photo of the service plug on my 2011 Two, rotated to match your photo.
See how the lever extends above the plug body.

So Crabtech, did that work? Are you back on the road?

Maybe Crabtech needs some time to cool off before answering? By the way, I learned this by doing it myself.

Sorry for the late reply. Since my Prius wasn't moving I decided to strip it and sound dampen everything:



I just finished putting it back together last night and pushed the plug up as depicted in the picture above. Now engine would start but would still give the warning screen! So I cycled the ignition a few times and the screen cleared!

Its interesting since I don't recall bumping that switch and it isn't intuitive that it locks in like that unless you see a picture of someone elses. Thanks guys for the help!

PS: However a new problem showed up:



Code pops up immediately after being cleared so its not a one time deal apparently. I'm probably going to start a new thread for this one unless someone has an answer right away...

Probably unplugged EVAP sensor.

Where is this sensor located?