315 vs 433 vs 902 MHz Key Fobs: How to Tell and Why It Matters

Most North American key fobs transmit on 315 MHz, most European-market and many newer North American fobs use 433.92 MHz (listed as 433 or 434), Ford's 2015+ PEPS smart keys use 902 MHz (868 MHz is the European equivalent), and Toyota and Honda run slightly off-standard variants at 312.09, 313.85 and 314.35 MHz. The frequency is fixed by the vehicle's receiver, so a fob on the wrong band will often program and pass the immobilizer but never operate the doors, and the tool will not report an error. Confirm the band from the FCC ID, the fob label or a frequency read on your tool before you order.

The four bands and where they show up

Listings that say 433 and 434 mean the same 433.92 MHz signal; suppliers round differently. Likewise 314 and 315 are usually the same 314.35/315 receiver family, although Toyota's 312.09 variant is a genuinely different setting that a fixed 315 board will not satisfy.

How to tell which frequency a fob uses

There are four reliable ways, in order of how often you will use them.

1. The catalog listing. Every Car Key Source vehicle listing carries a frequency field alongside the FCC ID and chip, so searching the FCC ID or part number gives the band without a second lookup. The find-my-fob tool filters by year, make and model.
2. The FCC ID. The code on the back of the fob is registered with the FCC, and the grant lists the operating frequency. Our FCC pages, for example HYQ1EA and M3N-A2C31243300, summarise the vehicles and band. The FCC ID lookup guide shows where the code is printed on each fob style.
3. The label or shell. Many remotes print the frequency on the case back or the board; Ford and GM fobs often say 315 or 433 outright.
4. A tool read. The Xhorse VVDI Key Tool Max Pro, KEYDIY KD-MAX and Autel KM100 all have a remote frequency tester: hold the working fob near the tool, press a button and the display shows the transmitted frequency. This is the only method that works when the customer's fob has no legible code.

If none of those is available, the vehicle year and make narrow it down, but the same model can switch bands mid-generation. The 2013–2016 Nissan Sentra is listed with both CWTWB1U815 at 433 MHz and CWTWB1U840 at 315 MHz; GM's 2015–2020 trucks run HYQ1AA at 315 while the Tahoe and Suburban run HYQ1EA at 433. Year alone would get both wrong.

Why a wrong-frequency fob fails silently

A key fob has two radios. The immobilizer transponder talks to the ignition or the smart-key antenna at 125 kHz, a low-frequency link that does not depend on the RF band at all. The remote (lock, unlock, trunk, panic, remote start) transmits on the RF band. When you program a fob on the wrong band, the transponder side registers correctly, the tool reports success, and the vehicle starts with the key in the ignition or the fob at the start button, because the 125 kHz side is fine. The remote side simply never reaches a receiver that is listening 100 MHz away, and there is no error path for that: the receiver does not know a transmission happened.

On a push-button smart key the symptom is confusing: the car starts with the fob held to the start button or in the backup slot (transponder mode over LF), but the buttons do nothing and passive entry at the door handle, which needs the fob's RF reply, is dead too. Techs then swap batteries, reprogram and blame the fob before checking the band. On a remote head key or flip key the symptom is simpler: the key turns the ignition and starts the car, but the buttons are dead.

The fix is a fob on the correct frequency; nothing in the vehicle can be reconfigured to accept the wrong one. This is also why "315 vs 433" is the first question a supplier's trade desk asks when a remote "programs but doesn't work". The key fob troubleshooting checklist runs through the other causes.

Ford: 315, 902 and now 434

Ford is the make where band mistakes are most common because the same generation ships in three bands. From 2015 the F-150 and most PEPS smart keys with 5 buttons and remote start moved to 902 MHz, while the 3- and 4-button smart keys on the same platform stayed at 315 MHz. In the catalog that is M3N-A2C31243300 at 902 beside M3N-A2C31243800 at 315, and later M3N-A2C93142600 at 902 beside M3N-A2C93142300 at 315. Flip keys split the same way: N5F-A08TAA at 315, N5F-A08TDA at 902, and the 2023+ N5F-A08TBLP at 434. The M3N-A3C108397 smart key for 2023+ Expedition and Mustang is 434 as well. Button count is a useful first clue on Ford, but confirm with the FCC ID; the Ford programming guide covers the rest.

Adjustable-frequency universal boards

A universal smart-key board with a switchable frequency removes the band question from stocking, because one board covers 315 and 433 (or 868 and 902) and the tool sets the band during generation. Car Key Source stocks Lonsdor's adjustable-frequency range:

Xhorse and KEYDIY offer the same idea in a few shells: the Xhorse XSADJ1EN Audi-style smart key covers 315, 433 and 868, and the KEYDIY KD-B21-4 knife-style flip is a 315/433 remote. Most other Xhorse and KEYDIY universal remotes set the band automatically when the tool generates the remote from its vehicle database, which is why they still need the correct vehicle selected. See the Lonsdor hub.

What Car Key Source stocks by band

• 315 MHz vehicle-specific: the bulk of the GM, Toyota, Honda (listed 314), Nissan pre-2013 and Ford 3/4-button catalog; browse by make at /keys/toyota or /keys/chevrolet.
• 433 MHz vehicle-specific: Chrysler/Dodge/Jeep fobiks and smart keys, Nissan and Infiniti 2013+, Honda 2016+ smart keys, Hyundai/Kia 2015+; browse /keys/dodge or /keys/nissan.
• 902 MHz vehicle-specific: Ford and Lincoln 5-button PEPS smart keys 2015+ at /keys/ford.
• Adjustable: the Lonsdor boards above.

If a key or remote won't program on the vehicle we listed it against, it is refunded within 30 days of delivery and we pay the return freight, which covers a listing error on our side; it does not cover a 433 fob ordered for a 315 vehicle against the listing, so read the band before you add to cart.

FAQ

Is 433 MHz the same as 434 MHz?

Yes. Both refer to the 433.92 MHz band; some suppliers and OEM labels round up to 434 and others down to 433, and the receiver treats them identically.

Can a 315 MHz fob be changed to 433 MHz?

No. The RF section of a vehicle-specific fob is tuned at the factory and cannot be retuned in the field; the only remotes that switch bands are universal boards built for it, such as the Lonsdor adjustable-frequency series, where the tool sets the band during generation.

Why does my fob start the car but the buttons do nothing?

That is the classic wrong-frequency symptom. The transponder side works at 125 kHz regardless of band, so the car starts, while the RF remote is transmitting on a band the receiver ignores; confirm the band with a tool read and replace the fob.

Which Ford fobs are 902 MHz?

In the catalog, the 5-button PEPS smart keys M3N-A2C31243300, M3N-A2C93142600, M3N-A2C940780 and M3N-A3C054339, and the N5F-A08TDA flip key for the Raptor and Ranger, are listed at 902 MHz. The 3- and 4-button keys on the same platforms are 315 MHz.

What frequency do 2018+ Toyota smart keys use?

Toyota's newer smart keys operate at 312.09 or 314.35 MHz depending on the model, which is why the Lonsdor LT30-02 board lists both; older Toyota smart keys such as HYQ14FBA are listed at 315 MHz.

Does the frequency affect the transponder or programming?

No. The immobilizer link is at 125 kHz for every band, so a wrong-frequency fob programs normally and starts the car; only the remote functions fail.