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Hi everyone, I had an odd thing happen with my car over the weekend and I am hoping you guys might be able to give me some insight or share your experience with me. I searched the forum and couldn't find a discussion of this problem. I apologize if this is something that I should have been able to find by searching the forums.

The car is a 2008 Mazda 3s Grand Touring, with about 123,000 miles on it. I've had it for about 4 years of totally worry free ownership. However, on Saturday I walked out to the car (in the winter cold), and the car was totally unresponsive to the key fob or key. I should mention it has never done this ever before, and I had just driven it about 2 hours before this happened.

Since the fob wasn't working at all, I manually unlocked the car and got in, which set off the alarm. I put the key in the ignition and turned it. But the the alarm continued and the car wouldn't start. The dash lights went on, but the starter was unresponsive.

I was able to walk to a watch battery store and they put new batteries in the fob. But that didn't work. I went back to the watch battery store and confirmed with them that the batteries were good, and that the fob appeared to be working. The guy even cleaned the contacts on the board in the fob. He also showed me that the small red light inside the fob was lighting up when the contacts were made. I went back to the car, but it still didn't work.

I then disconnected the battery and let the car sit for several minutes. I was hoping this would reset things and clear out whatever error was causing this problem. I reconnected the battery, and the alarm went off again and the key and fob were still unresponsive.

I ended up having the car towed to the dealership. It was the weekend and they were closed, so I just dropped it off. And then, of course, when I spoke to the guy at the dealership this morning, he said he walked out there and everything worked perfectly. He used the fob to unlock the doors and disarm the alarm, and the key fired the car right up.

They are going to run a diagnostic to see if they can figure anything out, but I am skeptical since everything seems to be working perfectly now. I am really worried about this ever randomly happening again, particularly if I am far away from home or if it happens to my wife when she has the car.

Lastly, I should also mention I bought the car used and it only came with one set of key and fob. I should also mention the car has a remote start, FWIW.

Is this a common thing, or is this pretty unusual? I'm hoping a new replacement key and fob would do the trick. But it seems like placing the key in the ignition should have disarmed the alarm and allowed me to start it up. Maybe not...

Any thoughts? I really appreciate any advice or expertise that any of you can offer.

Thanks!
 

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We purchased a 2007 Mazda 3 Sport in August 2018. Had to replace the battery about a year later so the battery is good. My daughter drove the car to join us for dinner and when she went to leave, the car would not recognized the key. We left it set overnight and I tried it again early the next morning - still didn't recognize the key. Called a tow truck and while I was waiting about 3 hours later I gave it a try and the car started. Took it to a mechanic and they couldn't find anything since it wasn't acting up at that time. It caused a problem a couple of time when I moved the car to clear snow. Again tonight it left my daughter stranded across town. Previously I had used the fob to lock/unlock the doors and it would start but that did not work tonight. The outside temperature has been about -5 degrees or colder both times it has left her stranded. Fortunately both times were in town and I could get her quickly.

Has anyone found a solution to this problem?

Thanks.
 

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We purchased a 2007 Mazda 3 Sport in August 2018. Had to replace the battery about a year later so the battery is good. My daughter drove the car to join us for dinner and when she went to leave, the car would not recognized the key. We left it set overnight and I tried it again early the next morning - still didn't recognize the key. Called a tow truck and while I was waiting about 3 hours later I gave it a try and the car started. Took it to a mechanic and they couldn't find anything since it wasn't acting up at that time. It caused a problem a couple of time when I moved the car to clear snow. Again tonight it left my daughter stranded across town. Previously I had used the fob to lock/unlock the doors and it would start but that did not work tonight. The outside temperature has been about -5 degrees or colder both times it has left her stranded. Fortunately both times were in town and I could get her quickly.

Has anyone found a solution to this problem?

Thanks.
The key has a internal transponder, which doesn't use batteries.
 

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My guess?? Maybe a low ambient temperature = low main battery voltage thing. When the car is brought indoors or jump started it warms up and the problem disappears.
 

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this is wierd looking at this since this just happened to me today. not so extreme though. i have a 2016 mazda 3. i live in florida so cold is not a factor, it was when i was leaving to work, i just do my normal routine i place my keys in the center console area and wanted to start up but the car did not do as i wanted, instead the start button started flashing green like it was not recognizing my fob. i literally tried for 15 seconds than i opened my driver door and tried again with success. it was wierd. and hopefully it does not happen again.
 

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Hi,

So, if the problem matches what i have encountered, its an issue where a small switch inside the key ignition barrel module goes bad (the switch either goes open or close)

So this particular part of the circuit is very simple, however not even Mazda japan were too sure about what was going on. Wasn't until I stumbled across another post for annoying door chime my suspicions were confirmed.

How to resolve. Two ways (in this case it was my stepfathers 2.3L and short of stripping down to a point i could access the microswitch (i assume) I took the easier and less invasive route)
1. Isolate the two wires attached to the connector harness plugs, detent the claws and cover the pins in heatshrink (i used Butyl tape).
2. Strip column down to point where the switch is accessible (I didnt do this so i wont be explaining this method at all). Replace the defective switch

PCM monitors this input and it does so by putting the input into a high state with 12v. (I wont go into details but the PCM inputs will be high impedance inputs). The other wire is ground. So what happens is that you put the key in, it hits the switch and the pin showing 12v will now be shorted to ground. This flows on to the digital logic inside the PCM.

In my case, this barrel would work momentarily. So by attaching a multimeter (with some nice clamping terminals) and monitoring DC Voltage i could actuate the switch and momentarily see the change.

What does this have to do with the immobiliser?
The PCM monitors for the Key Fob code, when it receives a code that matches stored ones, it then starts a chain event leading up to the toggling of the central locking. PCM will not toggle a lock condition if it sees that there is a key in the barrel.

How can you tell? The constant chiming.. Dead giveaway........Also, the barrel would make an unusual click and feeling. Unlike mine, it didnt feel right. This solution probably wont work if the chime is responding properly (door open with key in conditions).

So, isolate the wires, disconnect and cover the wires(leave them out of the harness. There are guides regarding the 'chime' issue that explain the process. This process will by the way effectively defeat the chime condition. - Yes, the car will still turn over, remote central locking and the immobilizer code are separate

What causes it. Heavy Keys...... The barrel dont like it..

He spent $600 approx for a mazda dealership to try fix, i did it in 20 mins..
 
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