Has anyone tried fitting a new battery and then doing a battery resrt so the car knows it’s got a new battery.
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I am not aware that the ND has this facility, can you tell us how we do this?
I think all mazdas from 2018 ish with stop start have a battery reset.
I cant remember it from the top of my head.
Something like.
Brake pedal and accelerator pedal pressed, ignition on, release and press accelerator 3 times whilst the istop light is flashing.
You will have to google it, i cant remember rhe full sequence
Sorry but I have just ‘googled’ it and there is nothing out there for a battery reset.
I have looked here NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION | 2016 ND Shop Manual (hexorcism.com) and as far as I can see you can replace a battery and all you will lose is some trip computer data.
I have disconnected the battery numerous times without issue, I believe you can just replace the battery without having to do any thing other than tightening the clamps firmly.
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There was a rather complex istop resetting procedure on the Web, but a battery disconnect seems to get the same results.
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Update!
I have just got my car back from the dealer who were investigating the problem of the P2502 fault code issues relating to this thread. They initially suspected the alternator and were going to replace it if the wiring/connectors were found to be ok. While it was in, the Service Manager rang me to tell me that they had recently had a notification from Mazda relating to the fault code and the symptoms described above. Basically Mazda had stated that they had found that these issues were related to a problem with the DC-DC converter on some cars. As a result I agreed to have the DC-DC Converter on my car changed at considerable expense. When I requested a copy of the document relating to the DC-DC Converter issue from the dealer, I was told that they were told by Mazda that they strictly forbidden to do this!
Does anybody know the position and function of the DC-DC Converter as I cannot find any reference in the online Shop Manual relating to this. Is it basically some form of transformer/inverter?
I really hope that this has cured my problems as it has cost me a great deal of money so far 
.
Cheers.
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Here’s hoping changing the DC-DC converter stops the random messages, pls keep us posted. I am however not very happy with a major car manufacturer keeping quiet on an apparent known problem.
The capacitor is <> 24 volt, the DCDC converter steps the <> 24 volts down to <> 12 volts.
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Thanks guys. Picture of the offending article replaced on my car that matches the diagram in the manual kindly given in the link by Scarletpimpernel. Strange that I couldn’t find it in the Online Shop Manual (Not Mazda issued). Anyway it is very expensive to replace!
Cheers.
Sure hope it does, and yes I will keep you posted.
UPDATE
So far so good. No more messages and the car seems to be behaving differently in that iStop function seems to activate much sooner after a cold start than previously, which suggests that the battery is being recharged much more quickly.
However, I still have the warm start (judder and stall) issue though, and have asked the dealer to contact MAZDA UK to see if they are aware of the problem (which does not throw up any DTC fault codes).
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Hello
Just suffered the false alarm of the iStop charging circuit failure on the M25. Slightly scary at night.
Car was driving fine and clearly getting charge from the alternator, no tell tale signs of battery light, dimming light output, or flickering rev counter. Fortunately Cobham service station was less than half a mile away so pulled up engine off, bonnet up. No loose connections were obvious so… turn the engine on…no surprise no more problems. Drove 30 miles home. Now it’s not driven daily and, for now lives outside. I’ve read the thread and it seems the finger points at the DC DC converter. If this is a known point of failure then Mazda should be prepared to replace the part, it’s not complex in principle as a part and the ND has been around forever. Mine is 2020 and 37k miles BTW. If this was a Lotus or an Alfa I’d understand it was “character” but by reputation the MX as a general type is supposed to be a robust and reliable car…or so I thought. If the flaw is the DC DC converter how much are they and what’s out there secondhand, or is there a superior alternative part or known fix, OR is this a Software glitch since a “hard reset” cured it, for now? If it’s SW glitch and upgrade available?
I’d welcome any input as I’ve been mildly disappointed and disconcerted by this… just wasn’t something I was expecting from what seems to be otherwise an excellent car. Thank you for any inputs you may have
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So about the DC DC converter replacement…
Did this cure the random false alarms?
According to First Rider (the poster) yes., at great expense.
Did he say how much?
I’ve seen DC DC converter replacement units at 500 dollars to 100 pounds on eBay
The unit seems easy to access so I’m guessing the labour is an hour max
Cost to replace was…?
Many thanks in advance
Hello
Did replacing the DC DC converter fix your random false alarms?
Was this an expensive fix, if it was a fix?
I’ve seen prices from 100 pounds to 500 USD
It seems very accessible so I’m guessing the labour cost isn’t too high
Thanks in advance
I also found this which may be relevant
In answer to your questions replacement of my DC/DC converter by Mazda cost me £1,300 and does seem at this point to have cured the problem (not many miles done though). Apparently the recall was for a different year of manufacture i.e .2015 as you state and did not include my 2019 model which even though it is the DC/DC converter I would hope that it was for a different fault. If these DC/DC converters are available on eBay, I certainly couldn’t find them and would be wary as to whether they were new/used and what year MX-5 they were suitable for etc. It would be interesting to know how many later DC/DC converters have proved to be faulty.
I think that I should have requested that they returned the replaced unit to me in case it could be repaired. Dealers never repair anything nowadays they just replace as they would not have any liabilities and they don’t care how much it cost the customer.
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It certainly would.
Many thanks for your reply, most helpful. At least I know the upper end of the cost!
Thanks 