I've a 2020 Mazda 3 Skyactive G Sport GT. Purchased with only 34000m 6 months ago. Thoroughly enjoying the car with no issues up until hitting a pothole!

Nearside front wheel damaged & tyre shredded. I hit a pot hole on a dual carriageway at 60mph. It was quite a severe impact causing the wheel to buckle.

A day later the dashboard lit up like a Christmas tree with an i-stop malfunction & Charging system malfunction -stop the vehicle.

An auto electrician found the grey connector to the DC Converter damaged & a wire disconnected. Replaced the connector & the DC Converter (a used one) & cleared error's.

Vehicle seemed ok & drove for 10 days until the same i-stop malfunction/ charging system malfunction returned.

U0298 error code will not clear. Tried another two used DC Converters with no joy.

New stop / start battery fitted & kept fully charged via CTEK Intelligent Charger. Tried to reset Battery management system but can't seem to get that to work?!

All high & low voltage fuses checked ok.

I've noticed that the alternator/ starter kicks off with an output of around 20v but slowly drops to nothing over 20 seconds of starting.

We're about to check continuity of the heavy duty cables that run from the DC Converter to the starter/ alternator.

Otherwise we're stuck.

I'd really appreciate any suggestions?

 

You first need to get your ECU properly scanned. What you described was someone that only cleared the active DTC(s) turned off the check engine dash caution light. Because no one looked at the other 2 areas of the ECU something was missed. The reason the original DTC(s) returned is because it was placed in another area of the permanent DTC(s) and as you cycled the engine over a few days the ECU complied reports from sensors and final reactivated the check engine light. Basically, to let you know that the cause of the original issue was not corrected.

START OVER
Maybe find a person that either knows where to look in the ECU or a real Automotive Diagnostic Technician or factory trained Mazda mechanic.

 

Welcome to the forum

 

Thank you Callisto. That's very helpful.
I have a license copy of FORscan but obviously not very familiar with it.
I've just found out a basic error on my part -
"Important: When it asks "Save profile?", click No or create a new one. You want FORScan to re-scan every module fresh, not load old data."

I've also found out how to "live test" the DC Converter in FORscan.

I'll have another go & keep you posted 👍

 

My first comment with one using forscan(aka 4scam) is to toss it in the garbage!

Find a quality scanning tool that you can connect directly to the OBDII diagnostic connector.

I can tell you how many times a month a customer comes in using that device and tell me what they found and how to fix the issue. And I can remember in the last couple years or more that those using it actually found the correct cause of an issue the first time around without part changing based on guessing a part caused the issue only to spend money change the part and it was not the problem. I often state on many forums that....
changing randomly thought parts that were thought to be the problem or cause of a problem often more times than not creates additional issues to the first unsolved open.
There is a reason what some of us pay to get trained and certified to use the proper diagnostic equipment and not rely on self teaching which really does not work out well for the DIY
Thoe other thing is people that use what you are often ion forum will post these lengthy live scanned videos thinking that that was where the problem area is at and then ask what other think. Those take more time then a glance to look at and again most of the time there is more need live scan shot to confirm thoughts and theories about an issue. In other words a waste of your time and you will likely get no response using them?
The other thing is that device is so different graphic as well how they report information in general then high end diagnostic scanners that professionals use.

I am not telling you not to post what you find only that a few of us that are better qualified to help may not because...4scam

 

Oopth! I genuinely appreciate the expertise you bring to the table. It's clear you have years of hands-on experience. I realize my initial comment may have come across as naïve and I apologize for that.
I'm learning, and comments like yours are actually really helpful for me (and likely others) to understand the gap between consumer-grade tools and what professionals use.

I actually did have a professional Auto Electrician look at it initially. They had high-end diagnostic equipment but lacked specific Mazda expertise/software. That likely explains why the "repair" only lasted 10 days—as you said, it probably just cleared the active code without resetting the permanent ECU logic, and it took that long for the drive cycle to flag it again.
I've been off work ill recently, so I am trying to avoid main dealer costs where possible. However, I do have a licensed copy of FORScan. I'm not very familiar with its deeper functions, but I understand it can do what the generic scanners missed. Would you have any suggestions on alternatives to 4scam?

Your point about part-changing without proper diagnosis is well taken—I can see how that leads to more problems and wasted money. And I hadn't considered how differently FORScan displays data compared to high-end scanners, or how that might make it harder for professionals to quickly interpret.
I certainly didn't mean to suggest that a DIY tool replaces proper training and experience. If anything, hearing from folks like you reminds me why I come to this forum—there's a wealth of real-world knowledge here that you just don't get from watching videos or tinkering alone.

Thanks again for the reality check. I'll be more mindful going forward about how I frame things, and I genuinely hope you'll continue to share your insights—even when correcting folks like me. It's appreciated.

 

To start

Look in the 3 main area's of an ECU
Current or active DTC(s)
Permanent DTC(s)
I/M monitors status.

The last 2 is the most commonly not look at area unless a person has been specifically trained in their service trade. An Auto electrician does not really qualify as such. That actual certification is totally different from a Diagnostic technician
__________________________________________________ __________________________________________________ ______________
A currently certified Automotive Diagnostic Technician should be able to have at least forum the cause of the issue in an hour or less regarding better then 90% of any issue that a ECU/PCM/ABS/SRS and a few other on board computers in most all but fully electric which these day you must have specific schooling or training an an automotive service institution specially for EVs. Or with ASE it is a L3 certification.
The device you are using is information overload for a DIY or other not actually trained. A simple hand held Diagnostic direct connection to the OBDII connector scanner for basic DIY level of trouble shooting is far better.
Most mechanics don't know how to read and understand an oscilloscope which that device you use in part simulates so data logging is great way to make sales to on that product making some think they will have the magic scanning device to solve all issues but in the end most get frustrated and delete all the application associated with it and the OBD uplink cable tossed into the garbage disposal. / LOL