Can a new key fob add remote start?

No. Factory remote start is part of the car, not the fob. Owner's manuals list it as "if equipped", and the remote start button only works on a car built with the system.

If your car has it, the replacement key needs the remote start button too. If it does not, the maker's phone app or an aftermarket remote starter may add it.

How to tell if your car has factory remote start

Look at the key that came with the car. A remote start button, often marked with a looping arrow, is a strong sign the car has it.
Read the remote start section of the owner's manual. It is marked "if equipped", because the manual also covers cars built without it.
Try it near the car. On a Ram 1500, press the remote start button twice within five seconds. On many Chevrolets, press lock, then press and hold remote start. The parking lights or turn signals flash when it starts.

Key page: Ram 1500 keys and key fobs · Chevrolet Silverado 1500 keys and key fobs

Why a key fob with a remote start button is not enough

The button only sends the request. The car does the rest: before it starts, it checks its own conditions. Ram's manual lists them: in Park, doors closed, hood closed, hazard lights off. A car built without the system has nothing to answer the button.

Order the key that matches how the car was built. Partexia reads that from the VIN.

Replacing a key on a car with remote start

Order the key with the remote start button. A key without that button cannot start the car from outside, even when everything else on it works.

Partexia shows the OEM key for the VIN, so you can see which one keeps remote start.

Toyota key fob remote start and Remote Connect

On many Toyotas with Remote Connect, the remote start button on the key fob works only while the car is enrolled in Remote Connect: during its trial, then with a paid subscription. If remote start on a newer Toyota key stopped working, check the subscription before blaming the key.

Key page: Toyota Camry keys and key fobs · Toyota RAV4 keys and key fobs · Toyota Corolla keys and key fobs

How to add remote start if your car does not have it

The maker's app. On some cars the maker offers remote start from its phone app. Toyota does it through Remote Connect on compatible cars, with a paid subscription after the trial.
An aftermarket remote starter. Installed by a shop with its own module, plus a bypass or data interface module so the car's immobilizer accepts the start.

A new key fob from the car's own range is not one of them.

Remote start key fob questions

Can I add remote start to my key fob?: Not by changing the fob. Factory remote start is equipment in the car, and a fob with the button only works on a car built with it. Partexia shows the key that matches the car's VIN.
How do I know if my car has remote start?: Look for a remote start button on the key that came with the car, check the owner's manual's remote start section, and try the start sequence near the car. To see the OEM key for the car, scan the VIN in Partexia.
Will a remote start key fob work on my car?: Only if the car was built with remote start. Otherwise the button does nothing. Partexia shows the OEM key for that VIN.
Why doesn't my Toyota key fob remote start work?: On many Toyotas with Remote Connect, fob remote start needs the car to be enrolled in the service, so an expired trial or subscription stops it. If you need a replacement key, scan the VIN in Partexia.
Does a replacement key need the remote start button?: Yes, if you want to keep remote start: a key without the button cannot start the car from outside. Partexia shows the OEM key for the VIN.