Intermittent "check charging system" error when decelerating
Hello, this is my first post. I did search the forum and didn't find anything relevant in the first few pages.
Vehicle: 2007 TSX, 103k mi. Recently purchased for my son to use for college. Car is in great shape. New battery and alternator in last 3 months.
Problem: When decelerating, between 30-20 mph, the "Check Charging System" error appears in the central information display, and the battery light illuminates. This lasts only a few seconds at most.
Details: charging voltage is normal at idle, 14.3 V. I have checked the alternator plug, both battery cables, and the negative battery ground connection. All are tight and clean. And here is the interesting thing: the error message will only appear if the car is decelerating and IN GEAR (this is the 5AT). If I drop into neutral during deceleration, the error will not appear. And if decelerating in neutral, I can reproducibly trigger the error by dropping the tranny in Drive.
Any suggestions for how to trouble shoot this? I'm thinking that the issue is mechanical, either a faulty harness or ground connection, and triggered by the engine/transaxle torquing on the engine mounts during a downshift.
Thanks in advance!