Mazda Forum - Mazda Enthusiast Forums - Multiple Codes 2012 Mazda3. U0100, U0101, U0121

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Quote:

Originally Posted by Callisto (Post 223243)

The voltmeter can only show voltage reading it cannot show the alternator state of charging nor can it show the state of the battery to measure CCA .

If you read the thread I recommended your battery age is likely when you bought it not how old it is?
After you load test check all the battery connection. At the terminals, starter and the most important the ground lead to the body.

The battery came back as good and all the lights and codes are gone today. Car is running fine for around 100 miles. Not entirely sure what to think.

Quote:

Originally Posted by Wing1 (Post 223265)

The battery came back as good and all the lights and codes are gone today. Car is running fine for around 100 miles. Not entirely sure what to think.

If the battery was disconnected from the Mazda it could have either been a connectivity issue or the ECU may have reset. Only a Mazda Dealership or a shop with a professional diagnostic scanner can enter the ECU and see the rest numbers (counters) and time logs to know for sure. So I would say wait and see and if no engine check light I would revisit the battery again and check all the leads to and from the battery.