Yes, and you put the positive back on with the negative connected. You ALWAYS start and end with the negative cable!! Less chance of spark or surge.

 

Interesting. Did OP fry PCM?

You check with a scanner and read diagnostic or real time data. If your ECU/PCM is fried you'll not be able to view any data from what I understand.

Check the positive terminal battery fusible disconnect. It's a plastic thing probably with a couple of nuts to fasten down main power wires. White and red perhaps. It's a long shot.

If you had to change your battery already, when did your car start dieing? Lots of electrical quirks to these newer cards for reset procedures that a lot of scanners can't really do even though it might say it can clear codes/DTC.

Let us know what happened. When it doubt, blame Mazda.. jk. But really....

 

He might have cooked something. Last year, I was working on my Jeep Grand Cherokee. When I went to start it, it wouldn't start and the dashboard lit up and windshield wipers took off. Pushing the button to off had no effect. After several minutes of futzing around, the only thing I could do to stop it was attach my portable jumping battery which stopped the wipers and allowed the start button to function and the engine to start. However, a number of features were disabled and several lights remained on the dash. I took it to the dealer who was able to clear the codes and return everything to normal. He told me they had seen several incidents of this with dying batteries. The OP may just have something like that, but he may also have cooked something doing the battery cables in reverse order.

 

Im having the exact same codes on my Mazda cx-5. Just wondering if you fixed it and what was the problem?

 

Mazdacx-5, have you had it scanned for codes?

 

Yes. Codes are:
B1207:86
U0415:00
U0121:00
B10c6:1f

 

I've asked this question on another thread so apologies for duplication.....but.....

I have discovered that the previous owner of my 2016 CX5 fitted a standard (cheap) battery to my car.
My wife was doing numerous short school-runs without a long enough journey to fully charge up the battery. We ALWAYS turn OFF the iStop function because, in very heavy slow moving multi-stop traffic, it was a complete PITA!
About 1 month ago we were out in the car and a warning message appeared 'Battery Maintenance System Malfunction' illuminating the instrument panel. I was able to 'hide' it using the info button, but a warning symbol triangle remained.

After searching the internet I discovered that standard 'cheap' batteries are no use with any iStop systems. So assuming that my battery had simply not had enough long rides to recharge, I used my smart-charger and fully charged the battery.
Next day, with the battery fully charged the warning message was off and I assumed everything was ok.
WRONG....
A few days later the warning re-appeared, so again I charged the battery and everything re-set itself.
Then MAJOR PROBLEM........
We were out in the car and ALL AT THE SAME TIME, the ABS, Traction Control, iStop, Tyre pressure warning lights ALL illuminated.
After ANOTHER battery charge, and the lights were all reset.......for a short while.
A few days ago........they are ALL back on, even with a fully charged battery, and they won't go off!

What can I do to reset them? I live on a remote island province of Philippines. It is practically IMPOSSIBLE to take it to a dealer!
The brakes seem to be working perfectly, even with the ABS warning light on, so IS IT SAFE TO DRIVE THE CAR?

At the moment I have disconnected the battery earth terminal and are again fully charging the battery. I'm desperately hoping that 24 or 36 hours without power may force a system reset.

Any ideas of how to resolve my problem? If I buy the correct battery, will it help to automatically reset the system when it 'senses' that it is the correct type?

 

I can't help you specifically, but I can say that some of those warnings can't be reset without the proper software and tools. A few years ago, I was working on my Grand Cherokee and when I went to start it, the windshield wipers started running, the dashboard lit up and it wouldn't start. To add insult to injury, pushing the start button would not take it out of start mode. I had to disconnect the battery. After waiting a half hour and reconnecting, the wipers were no longer running, but it still had numerous dash lights on and still wouldn't start. I jumped it and charged it, but the lights stayed on. Took it to the shop where they determined that a cell had failed in the battery. They had to reset the computer with their computer and replace the battery. The service manager said this is not uncommon with the newer cars.

 

Hi Mike,
Interesting that the source of the problem seemed to be from the battery! It is my 'Battery System Maintenance' warning light that has started this whole sequence of mysterious warning lights.
Unlike yours, mine starts perfectly well, and runs perfectly. The brakes work as normal even with the ABS light illuminated.
I'm going to take it to the battery shop where the 'incorrect' battery was purchased and, as it's still under warranty, exchange it for the vastly more expensive but correct specification battery and hope they give me full refund for the 'incorrect' one against the cost.

To put this problem into perspective, to take my car to a Mazda dealer on Philippine mainland I have to do the following......

Book and pay for the once-a-week overnight ferry to Manila (cost about $400).
Go to the police and obtain a certificate to confirm the car is not 'wanted' for any traffic violation! $$$$
Go to the coastguard with the police certificate and obtain a 'Clearance to Sail' authorisation! $$$$
Leave the car at the port THREE DAYS before the ship sails for them to load onto the boat (no RORO service here)
Book a flight to Manila (cost about $120).
On arrival after taking the car to the dealer and paying them whatever the cost is to reset everything, book into hotel for 6 nights (because the ferry only sails once per week) - Cost about $350-$400.
3 days before sailing take my fixed car back to the port, pay another $400.
Buy another flight ticket home - $120
12 hours after the ship docks, go and pay various 'port fees' and 'documentation fees' and collect the car.
Total cost probably $1500 PLUS all my living expenses while I'm in Manila!

So you can appreciate my predicament.

 

I can surely appreciate it. Sounds like you should plan this as a vacation and spend some extra time in the Phillipines to justify that expense.