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Discussion Starter · #1 ·
Hi, I hope this is the right place for this post.

I have some sort of weird electrical issues with the car, hoping someone can point me in the right direction.

Early in the morning, I started my Mazda3 2012 Sedan 2.0L, and everything went as perfect as usual. Then, I arrived to the place I supposed to arrive, and 30 minutes later, the alarm starts by its own (in this place where I am, I can see the car, so no one was near by). I turn the alarm off with my key, and 2 minutes later, the alarm starts to sound once again. This same thing repeats like 3 times. I went to see what was wrong with the car and see that the headlights were on (all the headlight switches were off), which was unexpected for me. I open the car put the key in the ignition switch, and when the key was on the On mode, the headlights turn off. Close the car, went to mind my own business and 2 minutes later the alarm goes on, I shut the alarm off and notice that the headlights were on again. This time I start the car, and to my bitter surprise, Check Engine and Traction Control indicator lights were on, and if that was not all, the car accelerates itself to the 2000 rpm, when normally its below 1000 rpm. My natural instinct was to accelerate the car, but to my surprise, the throttle pedal did not work!!, no matter what kind of pressure I put to the pedal, it just didn't work. I turn the car off. and 2 minutes later the headlights went on again and no alarm this time.

I called my mechanic, and suggested me that something went wet because the night before it rained like crazy, however, for me, this sounded weird, because in the early morning the car started with no problems.
My mechanic then told to unplug the battery, wait for 5 minutes, plug it and start the car, things that I did (by the way, I only unplugged the negative terminal). Now when I wanted to start the car, a completely dead battery!!. Someone, suggested me that it is the alternator, however, according to the user manual, when there are problems with the alternator, the battery indicator light turn on, and this is not the case, just Check Engine And Traction Control indicator lights are on, the last one, for me is a really bad sign.

After all this story, Can someone has gone through something like this? Do you think it's just a matter of changing the battery? A fuse maybe???

I share a picture of the dashboard with the engine on, showing the 2000 rpm, and the indicators lights.

Thank you all, in advance.

Speedometer Car Tachometer Gauge Odometer
 

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Hi, I hope this is the right place for this post.

I have some sort of weird electrical issues with the car, hoping someone can point me in the right direction.

Early in the morning, I started my Mazda3 2012 Sedan 2.0L, and everything went as perfect as usual. Then, I arrived to the place I supposed to arrive, and 30 minutes later, the alarm starts by its own (in this place where I am, I can see the car, so no one was near by). I turn the alarm off with my key, and 2 minutes later, the alarm starts to sound once again. This same thing repeats like 3 times. I went to see what was wrong with the car and see that the headlights were on (all the headlight switches were off), which was unexpected for me. I open the car put the key in the ignition switch, and when the key was on the On mode, the headlights turn off. Close the car, went to mind my own business and 2 minutes later the alarm goes on, I shut the alarm off and notice that the headlights were on again. This time I start the car, and to my bitter surprise, Check Engine and Traction Control indicator lights were on, and if that was not all, the car accelerates itself to the 2000 rpm, when normally its below 1000 rpm. My natural instinct was to accelerate the car, but to my surprise, the throttle pedal did not work!!, no matter what kind of pressure I put to the pedal, it just didn't work. I turn the car off. and 2 minutes later the headlights went on again and no alarm this time.

I called my mechanic, and suggested me that something went wet because the night before it rained like crazy, however, for me, this sounded weird, because in the early morning the car started with no problems.
My mechanic then told to unplug the battery, wait for 5 minutes, plug it and start the car, things that I did (by the way, I only unplugged the negative terminal). Now when I wanted to start the car, a completely dead battery!!. Someone, suggested me that it is the alternator, however, according to the user manual, when there are problems with the alternator, the battery indicator light turn on, and this is not the case, just Check Engine And Traction Control indicator lights are on, the last one, for me is a really bad sign.

After all this story, Can someone has gone through something like this? Do you think it's just a matter of changing the battery? A fuse maybe???

I share a picture of the dashboard with the engine on, showing the 2000 rpm, and the indicators lights.

Thank you all, in advance.

View attachment 107077
Hi, I hope this is the right place for this post.

I have some sort of weird electrical issues with the car, hoping someone can point me in the right direction.

Early in the morning, I started my Mazda3 2012 Sedan 2.0L, and everything went as perfect as usual. Then, I arrived to the place I supposed to arrive, and 30 minutes later, the alarm starts by its own (in this place where I am, I can see the car, so no one was near by). I turn the alarm off with my key, and 2 minutes later, the alarm starts to sound once again. This same thing repeats like 3 times. I went to see what was wrong with the car and see that the headlights were on (all the headlight switches were off), which was unexpected for me. I open the car put the key in the ignition switch, and when the key was on the On mode, the headlights turn off. Close the car, went to mind my own business and 2 minutes later the alarm goes on, I shut the alarm off and notice that the headlights were on again. This time I start the car, and to my bitter surprise, Check Engine and Traction Control indicator lights were on, and if that was not all, the car accelerates itself to the 2000 rpm, when normally its below 1000 rpm. My natural instinct was to accelerate the car, but to my surprise, the throttle pedal did not work!!, no matter what kind of pressure I put to the pedal, it just didn't work. I turn the car off. and 2 minutes later the headlights went on again and no alarm this time.

I called my mechanic, and suggested me that something went wet because the night before it rained like crazy, however, for me, this sounded weird, because in the early morning the car started with no problems.
My mechanic then told to unplug the battery, wait for 5 minutes, plug it and start the car, things that I did (by the way, I only unplugged the negative terminal). Now when I wanted to start the car, a completely dead battery!!. Someone, suggested me that it is the alternator, however, according to the user manual, when there are problems with the alternator, the battery indicator light turn on, and this is not the case, just Check Engine And Traction Control indicator lights are on, the last one, for me is a really bad sign.

After all this story, Can someone has gone through something like this? Do you think it's just a matter of changing the battery? A fuse maybe???

I share a picture of the dashboard with the engine on, showing the 2000 rpm, and the indicators lights.

Thank you all, in advance.

View attachment 107077
I am having an issue somewhat similar to yours. When my car is cold started the check engine and traction control lights come on.
Hi, I hope this is the right place for this post.

I have some sort of weird electrical issues with the car, hoping someone can point me in the right direction.

Early in the morning, I started my Mazda3 2012 Sedan 2.0L, and everything went as perfect as usual. Then, I arrived to the place I supposed to arrive, and 30 minutes later, the alarm starts by its own (in this place where I am, I can see the car, so no one was near by). I turn the alarm off with my key, and 2 minutes later, the alarm starts to sound once again. This same thing repeats like 3 times. I went to see what was wrong with the car and see that the headlights were on (all the headlight switches were off), which was unexpected for me. I open the car put the key in the ignition switch, and when the key was on the On mode, the headlights turn off. Close the car, went to mind my own business and 2 minutes later the alarm goes on, I shut the alarm off and notice that the headlights were on again. This time I start the car, and to my bitter surprise, Check Engine and Traction Control indicator lights were on, and if that was not all, the car accelerates itself to the 2000 rpm, when normally its below 1000 rpm. My natural instinct was to accelerate the car, but to my surprise, the throttle pedal did not work!!, no matter what kind of pressure I put to the pedal, it just didn't work. I turn the car off. and 2 minutes later the headlights went on again and no alarm this time.

I called my mechanic, and suggested me that something went wet because the night before it rained like crazy, however, for me, this sounded weird, because in the early morning the car started with no problems.
My mechanic then told to unplug the battery, wait for 5 minutes, plug it and start the car, things that I did (by the way, I only unplugged the negative terminal). Now when I wanted to start the car, a completely dead battery!!. Someone, suggested me that it is the alternator, however, according to the user manual, when there are problems with the alternator, the battery indicator light turn on, and this is not the case, just Check Engine And Traction Control indicator lights are on, the last one, for me is a really bad sign.

After all this story, Can someone has gone through something like this? Do you think it's just a matter of changing the battery? A fuse maybe???

I share a picture of the dashboard with the engine on, showing the 2000 rpm, and the indicators lights.

Thank you all, in advance.

View attachment 107077
I am having a somewhat similar issue with my 2012 Mazda 3. When I cold start the car the check engine and traction control lights stay on. This is accompanied by a rough idle and limited RPMs. If I shut the car off and restart it, only the check engine light stays on and the car appears to operate normally. I took it to my Mazda dealer. I was told that I needed a new PCM. They replaced it to the tune of $1700 for parts and programming. When I picked up the vehicle, it started with no warning lights and operating normally. After the car sat for a few days, I cold started it again, and the issue returned. I took it back to the dealership and they had the car for three weeks. At that point they told me that when they programmed the PCM, the program was corrupt, so they re-programmed it annd changed out a solenoid. Again I picked the car up. No warning lights and it operated normally on my drive home. However, when I cold started it again a few days later, the same issue returned. It is now been sitting down the Mazda dealer for over a week and they are still trying to figure this out.
There does appears to be a workaround. You simply shut the car down and restart it and it will operate normally with the check engine light on. However, I want to sell the vehicle and do not want to sell it while this issue exists. I will follow your post closely to see if you get your issue resolved. Conversely if I happen to get my issue resolved, I will post the outcome and the resolution.
 

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Discussion Starter · #3 ·
Wow, I posted my problem a long time ago. I was able to resolve it by myself (and with some mechanics help of course) no Mazda dealer involved and it turned out to be a fairly easy fix.

For my case, the resolution was:

As far as my investigation could reach, water is main the cause of failure for the PCM which is located below the parking brake lever (or the shifter lever, depends on your point of view).
So, the first step was to check if there was any water leakage in the sunroof. And it turns out, there wasn’t any. By the way, if you spilled a conductive liquid in that area (like water), the first suspicion is a PCM problem.

In my case, because no water was leaked or spilled, I discarded any PCM related issues.

Also, the user manual said that the battery indicator light in the dashboard is not a battery issue it’s an alternator problem, so I blindly believed in the user manual and discarded an alternator failure because that particular indicator was off.

… continuing with my story in the main thread...

After my completely dead battery happened, I needed to move the car somehow, so I took the battery to a mechanic where they recharge it. And to my pleasant surprise, the car started totally normal. But I was totally afraid that the car could fail me again. And so it did. I have to mentioned that the car was stopped for a complete day before the failure.

When I wanted to cold start the car, once again: Check Engine and Traction Control lights were on; 2000 rpms and no throttle; (I later discover that this is a mode that the car uses to protect itself from any further damages that may occur, and the 2000 rpms are for you to drive it to nearest mechanic).

So, the next thing in the checklist was a Battery Issue, and I did all the YouTube testing, hahaha. I test the Battery Voltage and it was ok: 12V. I tested for any battery draining, and there was none (there is a myriad of videos on YouTube to check for draining), There was also a test, to see if the battery was failing, it consisted on checking the voltage drop in the right moment of car cold start: if the voltage drop from the 12V to below 10V there is probably a battery issue. For me the problem was, that this voltage drop is actually really fast and you need to get a multimeter that can measure voltage dropping really quickly and I couldn’t get my hands on any of those, so I could not have any reproducible results from that test.

Long story short, I took the battery to my nearest autozone, they tested the battery and (un)fortunately it was damage. So, I bought a new battery, and all the car problems disappear. I connect the scanner, no error codes and all normal. (The battery scanner although showed a near 12V charge the amperage was really low, in other words a dead battery).

In your particular case, and relating it to my problem, I think the Mazda dealer is ripping you off, specially because of these quotes:

If I shut the car off and restart it, only the check engine light stays on and the car appears to operate normally...--
This is probably because the alternator charge your battery to a stable operation voltage and current. The engine light stays on, likely because the computer remained with an error code. If you want the error code to disappear, start the car, let it run for a few minutes, unplug the battery wait for a few minutes and then plug it again, the error code should go away
, and,

However, when I cold started it again a few days later, the same issue returned…--
This is probably because your battery is not able to hold the charge, and as the days go by, the battery is slowly discharging to a point where the car detects a problem.
Also, if you suspect that the alternator is killing your battery, when the car is idling, connect the multimeter to the battery and check that the voltage is not too high. In my little research, if the battery is 12V and the alternator is pushing more than 13.2V or 13.5V then the alternator is overloading the battery and killing it, this require an alternator change.
And check for any battery draining.

I you have access to a battery that is within the same capabilities of your Mazda and in a good condition, try swapping it. Start the car to see that there is no issues, if there is none, then,
rest the car for a day or two, cold start it and see what happens, if once again you see no problems then your battery is the problem.
Or, take your battery to an autozone so they can check your battery.
If this checklist fail, then, man, I’m out of any ideas.


Hope you can resolve your problem and looking forward for your outcome!!



…sorry If this responses are long, but I hope that these long stories can help anyone else so they can narrow a long list of problems to a just one.
 
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