Q: car keeps shutting off randomly on a hot day then after sitting it will start back up and repeat, no codes are being thrown

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so after i drive my car on a hott day it will shut off randomly then after sitting for a bit it will strt back up and shut off again, and no codes are being thrown

My car has 112000 miles.
My car has an automatic transmission.

This is a classic symptom of a module that is failing when it gets to hot. It could be as simple as a bad connection in a wiring harness. I’ve searched for any reports of this symptom for your Mazda, but this doesn’t appear to be a pattern failure for your year make and model. No matter. This is an easy diagnosis regardless.

The only challenge is recreating the problem. It requires a hot day and some driving to get it to fail. Once it fails, you need to see what is missing. Spark, fuel, injector pulse, a sensor has stopped working. Any electrical component is vulnerable to heat. Which one is failing when hot is what you need to figure out. Often times you can drive it with a scanner connected and monitor the data to see what is lost when it dies. Keep in mind, you will need more than a code reader that is sold at your local parts store. They often sell scanners, but they will be the more expensive scanners sitting or hanging next to the code readers.

The next challenge is what to monitor with the scanner. Most scanners will allow you to pick what PID (Parameter ID) data to monitor. This is necessary because most interfaces will have a large delay in data transfer if it is monitoring all the available PID’s at once. PID data is the term used by the manufacturers to describe data points your PCM (Powertrain Control Module) uses to make calculations.

I recommend choosing the crank sensor, cam sensor, RPM (Revolutions Per Minute), MAP sensor and or MAF sensor, and injector duty cycle. If the data from one of these fails or is out of spec, it is likely the problem. Of course, all these sensors are connected to the PCM. If the PCM is what’s failing, then this data will not be correct. Once you pinpoint what part of the system is failing, you will need to do some pinpoint tests while it is failing. Some vehicles utilize other modules to control ignition or injector pulse. There may not be one primary computer that is responsible for all of these PID’s. Because of this, you will need wiring diagrams. Not to mention access to a professional automotive information system to guide you in the testing of the suspected failed component.

I recommend Alldata for your information system. They offer access to information for one vehicle for one year for around $25. Keep in mind, navigating this software isn’t something that comes quickly. It will take time just to learn how to find the information you need.

If you find your unable to find the information you need, you will need to have technician diagnose your vehicles stalling issue. Keep in mind, this can be a time consuming process due to the nature of the failure.

What ever you decide, this is the basic process involved. Keep in mind, the knowledge and experience to diagnose this problem involves a thorough understanding of all automotive systems. If you feel you do, give it a shot. If not, give us a call so we can set up an appointment.

Good luck.

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