If you spend a little more ($100+) for a code reader that also displays “live data”, it can help keep you out of a pickle. Inexpensive scanners have a lot more capability than in years past - anything from TopDon is a lot of bang for the buck.
For instance a friend of the family had a car that set a misfire code and wouldn’t start - she was stranded in a parking lot - another friend of hers had a simple code reader that showed a misfire code. The misfire code doesn't tell you why it’s misfiring. Simple live data showed the car engine temp sensor reading was way way off and It took 5 minutes to unscrew the old sensor and screw in the new one.
While on vacation the engine starts running poorly, but doesn’t set a code. Looking at live data you see engine air supply signal (mass air) is really low - that’s often a dirty sensor or maybe a bug caught on the sensor, or a plugged up air filter. Another 5 minute fix.
Your car barely started and then the worry is the battery is shot - looking at live data shows the alternator isn’t putting out the right voltage, so it’s not the battery. On the flip side it could the situation where the alternator voltage is good, so the battery or battery connection is bad. Even if a low voltage code is set, it wouldn’t give any helpful information as to why.
