no start replaced battery still no start . just a single click. would this be the starter ?

I would check the cables and the ground and main fuse/relay, next step after that would be to check the starter.

where would I find the main fuse relay? I have checked cables and grounds,

You can also take a multimeter and put the positive lead on the starter solenoid positive post and the negative lead on a ground and then have someone turn the ignition switch. If the meter reads 12 volts, then you probably have a bad starter solenoid. If you're getting less than 12 volts you can check starter relay, neutral safety switch, ignition switch.

The factory alarm might also be the culprit, it seems these factory alarm cause the same issues you are having. http://forums.mazdaworld.org/101-323-protege-protege5/46857-mazdaspeed-protege-won-t-start-2.html

Sorry wrong link:http://www.mazdas247.com/forum/showthread.php?123843086-old-member!-new-car-but-starting-problems

Im having the same problem how do I fix it

replace cables or connectors going to the battery. The get caked up with battery acid and corrode easy.

I had the same problem - strange how no one ever finishes these posts with the answer?? Problem was on a 2008 Mazda 5 2.0 manual (irrelevant) - was told various things e.g. BCM gone bad, fuse box seam rotted, immobiliser etc. Some days it started some days it didn't would usually not start after a few short journeys but not always and whenever I asked a garage to check it, it strangely always started so the issue could not be diagnosed. I decided to get a wiring diagram and workshop manual as a free download and look myself (cant remember the forum with a link to this but there is one for the mazda5). Now, if the starter relay is clicking when you try to start it is nothing to do with the PCM/BCM/immobiliser because these systems would kick in PRIOR to the click they do not stop the engine from cranking after the relay operates they interrupt before this happens - if the relay clicks its an issue with the wiring on the engine side of the main fuse box ( this is in the engine bay next to battery box) or if you are very unlucky its the starter solenoid or starter motor. There are loads of posts on the web for checking a starter motor and solenoid so I will let you look for them. As a warning, I sent mine to a garage to have the starter and solenoid tested, as usual it started fine with them. They said they had checked the starter etc and it was all good so I dismissed this as the cause, they clearly had looked but not really investigated. On the Mazda 5 the starter motor is on the front of the engine and a real pain to access or even find. You need to go from underneath unless you have very small hands. I have just finished putting the car back together and so far so good, I traced the wire from the fuse box relay (unfortunately it was not refusing to start at the time so I could not test the wiring for the fault) The relay sends the current via a red and yellow wire to the starter solenoid (if you are not a home mechanic type the solenoid is the smaller cylinder on the starter motor) this red/yellow wire is much thicker than the others from the fuse box and is easily identified. Look at the fuse box, there is a connector with loads of wires coming out of it between the relays and the fuses - look for the thicker red and yellow wire on the left as you look from the front. When the relay clicks it allows 12V to go down this wire to the starter solenoid and that tells the solenoid to allow the starter to crank. If mine had been refusing to start at the time I would have checked this wire by running a wire from the battery positive terminal to the solenoid where this wire is connected with a spare piece of cable (household cables are fine for this just pull one from a broken lamp and ensure the copper is touching at both ends of your temporary bypass) get a friend to try and start the car as you do it. If it starts then this was your problem. When I traced the wire it ended with a female spade type connector (a plastic fitting on the end of the wire) which attaches to the male connector on the solenoid (rectangular metal spade shape about 3mm wide and 5mm high - its on the left side of the solenoid as you look from the front) it pushes on but does not lock in place so you can just pull it off. The female/male connectors are poorly designed, the fit is not tight and they corrode. On mine the male end was corroded and dull nothing extreme but very dull - I couldn't see the female end because its encased in plastic but I guess it was the same. Cleaned the male end with wet and dry paper until I could see the metal and used a thin blade to scrape at the inside of the female end. Spray some electrical connector cleaner in there, push it back on and you are set to go. This seems to be the answer but I will get someone to replace the female connector with something that fits better because vibration from the engine could work it loose and its going to corrode again. I think the battery can sometimes jump the gap/corrosion and sometimes not so the fault is intermittent probably worse when you do very short trips and the battery can not recover full charge before its asked to put a full load on the starter and cant jump the gap/corrosion. Anyway tried to write this so anyone can try and save a few pound/dollars - hope it helps,