Won't hurt to install the battery,but I'd check voltage and charge it if necessary to get to 12.5-12.8 volts. Make sure you're charging no more than 14.5 volts with the new ecm.Check voltage on the battery first thing the next morning. If it's holding over 12+ volts,the battery should be ok. You can also use the meter and do a load test yourself.Doesn't have to crank up as you can pull the plug cap for this test. Have someone crank the engine over and you look at the battery voltage as it's cranking. Voltage should stay between 9.5-10.5 volts under a load if the battery is in good shape.If it drops lower than 9.5 volts,may be time to replace it. Look at this article on testing batteries. https://www.batterystuff.com/blog/ho...ry-is-bad.html