2010 Prius Wont Recognize fob key, replaced 12 v battery and fob battery, anti theft blinking

does the red fob light illuminate when you push a button?

do you have any way to check for trouble codes?

 

The lock symbol on the display only indicates that the keyless system is trying to detect if a smart key transmitter is present. It is not a security system.

If you installed the wrong battery or a bad or weak battery into the key fob, no signal is produced by the key fob transmitter. I recall, you need the 3 volt battery. I do not immediately recall the number.

There is a chip in the fob right under the chromed Toyota symbol on the fob. A fob with a dead battery can still work by holding the Toyota symbol to the start switch and pressing the clue start button. If this works, replace the battery in the fob and try again.

 

My 2010 shows a warning on the dash if low fob battery is detected. Maybe a Canadian model thing though, not sure.

Test both batteries, for starters. With just a multimeter set to voltage, the fob battery for sure should be over 3.0 volts (IIRC I've gotten the warning on the dash even when it was right at 3.0), and the the 12 volt battery (test first thing in the morning) should be mininum 12.5, but brand new should be at least 12.6, though 12.7~12.8 is healthier.

Fob battery should be CR 1632, at least according to my notes.

 

I just replaced my keyfob battery last week, so I tested it with a multimeter. The old battery that kept giving me dash warnings was 3.03V (manufactured by Eunicide). The new fresh battery was 3.32V (which I ordered online from China).

I would try starting the car with both keyfobs (if you have a second one) to rule out if it is a keyfob problem. The keyfob should be able to lock/unlock your car remotely if it has power and is working.

 

I order stuff thus too, but it tends to be things nigh impossible to find locally.

Which sadly is more and more these days. For batteries I just walk over to the mall, pay through the nose. There's a rumor our mall is slated to be torn down soon, replaced by highrise condos.

One more thing: if I get the fob battery warning on one, I replace them both, kinda like headlights I guess: if one's going, the other's likely not far behind.

 

Is it possible, one of the battery jumps could have been polarity reversed if so there's a fuse or fused link that gets fried?

 

USA models have the same warning. A fob with a weak battery will function for quite a while until it doesn't.

The last time I bought fob batteries I could buy a full card (8?) on line for what one sells for in a retail store--after looking on line for a retail store with one in stock.

 

i think you need to start with the 12 volt battery health test, and the tightness and cleanliness of the connections. especially negative to ground.

 

We don't know what the SOC (state of charge) of the recently purchased 12V battery is. A low SOC could cause what you are seeing as various ECU's fail to initialize. That could explain why some systems (lights, horn) work while other electronic controlled systems don't. My suspicion is turning toward wiring damage, maybe by rodents. Or something electrical was disconnected in the process of battery replacement and has not been reconnected.

 

This indicates the fob is powered normally

I would focus on the "new" 12V battery. What should happen if the fob was dead would be "Key Not Detected" when you press the brake pedal and push the power button. Then another note pops up saying to hold the fob next to the power button. At this point, the green LED comes on in the power button and you are able to start--even with a dead fob.

 

I don’t think there is any way you can bypass the immobilizer. A failed body control module can cause similar symptoms. You might need to get a locksmith or someone with a good diagnostic tool.

Do you have 2 smart keys / key fobs?

Will it lock/unlock with the switch on the door?

On both of my Toyotas, if I have a dead smart key battery, I have to hold the Toyota emblem on the back of the smart key directly on the start button on the dash. It can’t just be near it. It needs to be right on it.

 

Some questions:

• Can you measure the voltage of each battery this morning before you try and do anything to your Prius?
• You say you’ve had your Prius since last August (2017 or 2018). Did any event bring on this behavior?
• Was the 12 volt in the Prius the original (do you still have it or look at the date code prior to removal)?
• Any recent electronic additions to your Prius?
• Any damage to the door mechanism?
• Where did the AAA guy perform the jump (at the back of the car or under the hood)?
• Did you watch him perform the jump or where he tried to connect it?
• Have you checked for blown fuses, particularly under the hood?

Good luck and keep us posted .

 

It sounds like this isn’t your first rodeo with jump starting your Prius .

What I would do is get a multimeter and determine what the parasitic draw is and how much it is.

In the 9+ years I have owned our 2010 with 193 k miles on it (bought it brand new in August of 2009), I have never jump started it. To me that is a concern and something I would do first off as anything can happen when electricity is involved. The risk is higher when in a hybrid too.

Have you checked the fusible link in the fuse box? If the AAA guy was struggling, he could have reversed the polarity causing the fusible link to blow. Hopefully that’s the only thing that got damaged cause if the reverse voltage got passed this, one of the next stops is the inverter and it could damage that.

Good luck and keep us posted .