I did not get the codes checked. I have a feeling that the codes came cause the car sat for extended periods of time or something else triggered the code. I have noticed that highway driving gets me 35+ mpg and longer local drives get me about 34mpg. The shorter drives seem to be terrible for the battery.

 

They are certainly terrible for economy, and they aren't necessarily good for the battery.

There is always a net input into the battery for a given drive IF the battery is kept at the target SoC (about 60%), i.e., if you start the drive and end the drive at 60% SoC, the net current to and from the battery is always < 0 where negative current/capacity = charging.

Failure to drive sufficient distance causes the SoC to drop below target, which means it's parked in an even lower state of charge - a great way to take a marginal battery over the edge.

 

Techstream

 

These are my techstream numbers. I think the battery is ok!

 

If the car is just sitting there, then those numbers have almost no diagnostic relevance as resting voltage is not indicative of health.

 

How do I check if the battery is good?

 

Display only block voltages, SoC, MIN/MAX voltages/blocks, and current. Start recording.

Place car in "N".

Turn on the:

A/C full blast with fresh air intake
rear window defroster
lights

Discharge to 20% SoC in "N".

Place car in "P", turn off A/C, defroster and lights, and allow car to charge battery.

Terminate recording and export to CSV.