The flat branded face is plus unless a mark in the shell says otherwise. The cell usually fitted is a CR2032 or a CR2016, matching the stamp, and the key is a smart key, flip key, or remote-head key. People who searched toyota key fob battery polarity still have one rule to follow. Read the stamp on the old cell, because that stamp wins.
Read the stamp before polarity
The coin already in the shell is the buying guide for polarity.
CR1632 is reported for polarity on some mid-generation smart keys, including certain Prius shells.
The CR2016 you might buy for polarity is 20 mm across and 1.6 mm thick.
Every one of those coins, in the case of polarity, is a 3-volt lithium cell.
A rechargeable LIR2032 does not belong in the shell for polarity.
A mark molded into the plastic wins over habit during polarity.
Right-hand drive does not change the coin you buy for polarity.
Touching a dead smart key to the start button is a separate backup, not the shopping step in polarity.
Close the cover fully before you test polarity from outside the car.
A brochure can list two keys for one car, and polarity still follows the shell you are holding.
If the shell in polarity is a new undocumented shape, the pry method is not confirmed.
Look for a plus sign molded in the well before you trust the habit.
The same rule applies to a CR2025 or a CR1632 if that is the stamp.
Match the cell for polarity
A push-button smart key from the 2010s onward usually takes a CR2032 when you are doing polarity.
If two reliable notes disagree about polarity, the page says they disagree.
The CR2025 you might buy for polarity is 20 mm across and 2.5 mm thick.
Same voltage does not make the coins interchangeable for polarity.
Almost every Toyota fob takes one cell, and polarity is not a two-cell case.
A battery-only swap for polarity does not require programming.
Base grades often kept a metal key after a higher grade moved on, which still matters for polarity.
Keep the spare coin for polarity in a cool drawer, not on a dashboard.
A gap at the cover, during polarity, means the coin is too thick or a clip missed.
Japan, Australia, Europe, and the US can print different grade names around polarity.
A bZ4X-style shell is not opened with an older Camry method during polarity.
The shell mark wins when it disagrees with the branded face.
After it works, lock and unlock once from outside.
Keep the wrong parts out of polarity
An older remote-head key or flip key usually takes a CR2016 when you are doing polarity.
CR1616 is uncommon for polarity and is not the default older Toyota cell.
A CR1632 reported for polarity is 16 mm across and 3.2 mm thick.
A CR2450 is the wrong coin for polarity.
This site does not invent a two-battery fob for polarity.
After polarity, lock the car once from outside and then unlock it once.
Grade names used for polarity belong to that market, not to a borrowed US list.
A pharmacy coin and a dealer coin are the same job for polarity when the stamp matches.
Do not stack a second coin as a shortcut for polarity.
The work of polarity stays a cell swap on a hybrid.
If the stamped coin is seated and polarity still fails, the fob has failed. Stop.
A coin seated backward leaves the buttons dead even when the size is right.
Close the shell after polarity
CR2025 appears for polarity only on some older compact remotes.
The CR2032 you might buy for polarity is 20 mm across and 3.2 mm thick.
A CR1616, uncommon for polarity, is 16 mm across and 1.6 mm thick.
An A23 battery is the wrong shape for polarity.
Plus, while you handle polarity, is the flat branded face unless the shell mark disagrees.
A hybrid badge does not change the coin you buy for polarity.
A never-paired extra fob is outside polarity. A dealer or licensed locksmith does that work.
A date code on the blister for polarity tells you the coin is fresh. It does not choose the size.
Do not slip foil under the coin as a shortcut for polarity.
The work of polarity stays a cell swap on a right-hand-drive car.
Write the stamp on the spare sleeve when you finish polarity.
Turn it over once and test. Do not add a second coin on top.
Pages that sit beside polarity
Continue with How to Replace a Toyota Key Fob Battery.
Continue with the page What Battery Does a Toyota Key Fob Take.
Continue with the write-up on Toyota Key Fob CR2032.
Continue with notes for Toyota Key Fob Not Working After Battery Change.
Continue with How to Open a Toyota Key Fob.
Hold this page to the shell
On the Toyota Key Fob Battery Polarity page, one stamped coin is enough.
On the Toyota Key Fob Battery Polarity page, the old stamp is the purchase.
Questions answered only with the facts above
Which face is plus?
The flat branded face, unless the shell mark says otherwise.
What if the shell shows a plus?
The shell mark wins.
What does a backward coin do?
The buttons stay dead until you turn it over.
Does the stamp still win for polarity?
Yes. The stamp on the old cell wins over a chart or a photo of another year.