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I had a locksmith program 2 keys, a new one and a used one for $45 each. He used some kind of wireless device to do it, so I don't think it's a DIY job. The hard part is finding a locksmith who is equipped to do it.
 

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I had a locksmith program 2 keys, a new one and a used one for $45 each. He used some kind of wireless device to do it, so I don't think it's a DIY job. The hard part is finding a locksmith who is equipped to do it.
That's funny...I was awaiting for someone to reply. Since David left zero info about his car including year, you hansboomer are a clairvoyant.

Yes it is difficult to find a locksmith who has the electronic tool to program keyless entry fobs. I have commented extensively on this topic on other threads and losing a key fob on a road trip with no back up plan can be a huge and expensive venture, up to and including having to have your car towed to a Mazda dealership.

BTW, I have a 2017 3 GT hatch.
 

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That's funny...I was awaiting for someone to reply. Since David left zero info about his car including year, you hansboomer are a clairvoyant.

Yes it is difficult to find a locksmith who has the electronic tool to program keyless entry fobs. I have commented extensively on this topic on other threads and losing a key fob on a road trip with no back up plan can be a huge and expensive venture, up to and including having to have your car towed to a Mazda dealership.

BTW, I have a 2017 3 GT hatch.
We're in the 2014-2018 Mazda 3 forum section, they're all the same, regardless of trim level. I don't think there's any difference even with the models with advanced keyless entry. All the keys should be the same because they're all keyless push button start.

In other words, all BM and BN are the same as far as keys go, with the difference between the hatch and the sedan being the only material difference (sedan has boot open button and hatch doesn't).

If I'm wrong, please correct me.
 

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We're in the 2014-2018 Mazda 3 forum section, they're all the same, regardless of trim level. I don't think there's any difference even with the models with advanced keyless entry. All the keys should be the same because they're all keyless push button start.

In other words, all BM and BN are the same as far as keys go, with the difference between the hatch and the sedan being the only material difference (sedan has boot open button and hatch doesn't).

If I'm wrong, please correct me.
Sorry David, you made no initial indication of Keyless entry, not all Mazda's have keyless entry in those years, in all regions, and also there is nothing that precludes anyone with a prior year Mazda to ask the same question which happens all day long here.

In short if you are inquiring about a 2014-2018 Mazda with keyless entry, the locksmith is not programming the remote, they are programing the CMU to find the remote. Therefore, special and limited equipment is needed by an authorized locksmith to have that equipment which is plugged into the OBD.

I, along with others have commented extensively on this topic on other threads. Keyless entry has some tech advantages, but there are some serious issues if you lose a fob and you don't think in advance how you are going recover. Also, there are some other security issues as well which are discussed elsewhere.
 

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It can only be done per service manual if I recall correctly, you must have 2 original key fobs. It can also be done with 1 key fob but you will need an OBD tool as mentioned above.


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It can only be done per service manual if I recall correctly, you must have 2 original key fobs. It can also be done with 1 key fob but you will need an OBD tool as mentioned above.


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Also, I can tell you from experience, if you are programming additional fobs ...make sure you have them all with you when they do the programming. It is both for your protection and to make sure all key fobs work properly after the programming is done. As Nostalgichero points out it can be done with one, but the 2nd one is for your protection in case something goes wrong with the programming of the new fob. When I did it the first time wanting to have a 3rd fob programmed and the programming was being done at the locksmith's brick and mortar and not mobile, the locksmith sent me home to get the 2nd working fob.
 

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Also, I can tell you from experience, if you are programming additional fobs ...make sure you have them all with you when they do the programming. It is both for your protection and to make sure all key fobs work properly after the programming is done. As Nostalgichero points out it can be done with one, but the 2nd one is for your protection in case something goes wrong with the programming of the new fob. When I did it the first time wanting to have a 3rd fob programmed and the programming was being done at the locksmith's brick and mortar and not mobile, the locksmith sent me home to get the 2nd working fob.


And how do you do that?

If one has a new car.... with BOTH key fobs... how can one program a 3rd (as the OP asked)?
 

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And how do you do that?

If one has a new car.... with BOTH key fobs... how can one program a 3rd (as the OP asked)?

You can have up to a total of 6 key fobs programmed for your car.
Programming of fobs requires special gear that connects to the DLC-2 data port. Your dealer has MDS, i had a local IT guy with a tool from china that worked at $40. The programming is under the PATS system created for security purposes it must be tough to crack. Even the powerful FORSCAN tool is not set up to program Mazda fobs.

And just like "2017mazda3" stated bring all keys... because the best procedure is to clear all and then program the fobs back in 1 at a time.

I learned the hard way, (for my 2017 3 GT) that while i was able to program a second fob (with the trunk release designed for sedans) as my second and it works... it also turns on a DTC red-light on the dash.... incorrect fob.....makes sense... but too bad. My 2nd learning experience i thought for my 2nd fob i'd use my wife's 2nd (2014 3 GT) while this program well into my 2017..... when i returned home i found that the key fob would no longer function for my wife's 2014. In other words the pairing is two way...and a fob can only be used for one car.
 

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To be clear and more accurate in terms of what is really being programmed, the CMU is being programmed and not the fob. You are teaching/programming the CMU to communicate with/find the fob and that is why it is important to have all fobs with you when you want to program additional fobs. It's really a safety net. There are multiple scenarios during programming where the outcome is bad and some are worse than others....including who and where you are programming your fobs and the reason you are programming a fob including...a lost fob on a road trip. It's always possible that the programming of the new fob to the CMU could clear out any existing fobs while failing to program the new fob. If you are at a Mazda dealership, then you're covered as they can resolve. If you are dealing with a locksmith, then there could be issues.

My alter ego is "Sammy Safety" so I will let you in on a secret as I am a freak about possibly losing a key on a road trip, or anywhere for that matter, dropping it in the pool or ocean, etc. I have a hide a key hidden on my car and a fob hidden inside the car (battery removed). The worst case scenario, and this is true and confirmed reality...if you are on a road trip or in the middle of no where, meaning not being able to locate a locksmith who has the proper electronics, updated codes and specific key fob, you will have to have your car towed to a Mazda dealership for them to program new fobs. This scenario obviously isn't exclusive just to Mazda. Think about all the costs and hassles of losing a fob with no back up plan. Also, the initial locksmith I went to (whom I deem incredibly competent) also had a difficult time cutting the copy keys and had to recut multiple times to make them work properly.
 

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Aaaaaand no, it is not the CMU being programmed.

To be clear and more accurate in terms of what is really being programmed

The way these keys work is they have 2 different radios inside. There is an LFID (125khz) and a 433mhz(?) radio. When the key is in proximity to the car, the car sends out a LowFrequency pulse from each antenna. The keyfob in return modulates that radio frequency so that the car's antennas can see which antennas are affected how. The 433mhz radio in the key is for the different button presses. Finally theres a PATS chip as well which is for the backup battery dead deal. The car has 3 different types of receivers: There is the keyless receiver module which connects to the SSU (start stop unit under the steering wheel). This module is in charge of the lock/unlock key presses. The second receiver is the PATS loop inside the start-stop button. The last module is the LF unit located at the driver footwell. That is in charge of generating the high voltage needed to challenge the proximity Low Frequency radio in the key fob. Notice all of these go to the SSU, not the CMU. Your SSU is your vehicle's immobilizer. It talks to the RBCM over a dedicated serial line and to the PCM over the general CANBUS. If the SSU detects an incorrect start/not authorized start, it will inhibit the PCM and TCM's operation. The engine will shut off and the trans will be blocked from shifting. A DTC "Vehicle Theft Detected." will be thrown.

Little side note, If you put your ear close to the LF unit, you can hear at a varrying period the pulses it sends. They will be quiet, high pitched whines. Kinda neat.

All of this basic background aside, unless the car has a regular turn key ignition (which I do not think any 3rd gen 3 has because even the base models have push start BUT NOT ADVANCED KEYLESS ENTRY), programming new keys in is the same.

I have not tried programming in a 3rd key from the car itself so I do not know if that procedure works or not, but I have programmed in a couple extra keys. One I added had the trunk release button ( I wanted to use it to fold my mirrors from the remote) That, like someone else pointed out, throws a DTC that it is the incorrect key. I ended up programming that into my mazda 6 instead. Then I programmed a regular hatchback key into my mz3 and it worked without a problem. You basically have to teach the PATS system what key it is and that identifier will work for the PATS, LF, and RF transmitter radios in the key fob.

You do not necessarily need all the keys because there are a few different ways to program them in using the OBD2 unit. One is to delete all keys in the system and start over, the other is to just add a key. Every key that is added needs to be programmed to the car. Then all keys need to be confirmed. That being said, you theoretically just need the key that is being programmed there. Then the next time you use another key you just tap it to the start stop button quickly (might not be necessary)

This programming was done with an OBDSTAR F100. Cheap on amazon. Works well.

Finally, each key is paired with the car. it is like the rolling code system on garage door clickers. The car has a challenge and the key fob has a response and these change on every successful communication. This is to make sniffing the signal from the remote and duplicating it all the more difficult. This means that there is effectively a mathematical equation tying a key fob to a car. The car does not really care if theres a response to the equation or not since it stores up to 6 keys (ie more than one). If you try to reprogram the key to a second vehicle with the intention of being able to use one key for 2+ cars, it will overwrite the "equation" on the key that is tied to the first car and make it unusable for it. The first car will see the key but the key will not be able to authenticate with the car's expected result so the car just ignores it.

If you need to program a new key, try whatever method is in the service manual. But be very sure theres no way you can delete the existing keys and effectively brick your car temporarily. If you exhaust your options and can't afford the OBDSTAR, PM me and ill send you mine if you cover the shipping.
 

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I had problems with programming an additional key. I could never have done it alone and it really annoyed me. I was really reluctant to use locksmith, but it was to expensive to go to mazda for help. I decided to give locksmiths a chance and I searched locksmith near me. That is how I have found Emerald Locksmiths and I was really lucky do have found them. Their locksmith came to me and did an amazing job with programing the key. It was done quickly and really was not expensive.
 
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