Hello. I recently replaced my alternator on my 2014 CX9 and the battery light comes back on a few minutes after starting. Also installed new belt and battery. It sometimes will go off but always comes back. I checked the blade fuses and all ok. ???? Voltage is 14.7 at battery while running.
Initially I got P0882 TCM power output low but cleared it and now no new codes but light still on

 

Welcome to the forum

 

What was the reason to replace the alternator?

Did you get a DTC. On your year and model the ECU controls the charging output of the alternator.

 

Initially I got P0882 TCM power output low but cleared it and now no new codes but light still on

 

Thats because you did not service the cause and clearing only turned off the indicator light caution. If you go back into the permanent file area you will see that DTC still there and every time you cycle the engine it gets added to your counters as an unresolved issue.

DTCs are a way to start the process to check for the cause but they are not always the exact cause of an issue.

 

Thank you. Any suggestions for next steps in the diagnosis from P0882 TCM power output low?

 

Sorry it is hard to teach how to do Diagnostic servicing . The best I can do to help you is this

Free Car Service Manuals from Operation CHARM — No strings attached!

When you find DTC you then need to look for all other possible condition like your monitors and permanent files. Then you need to determine which was cause and which was effect. So, unless you get a basic study of Automotive diagnostic trouble shooting you need to remember first the DTC does not always represent the actual pert or system as fault and then set up a service check tree of check and eliminating possible causes.
It helps also to have all the proper shop level diagnostic scanners and also other tools like digital volt/ohm meter.

The other is wait for the countless guessing from member on a solution that eventually one may work ..

Or invest in a 1 hour service diagnostic service charge. But if you do this make sure the shop or dealership service has a current certified Diagnostic Technician or factory trained Mazda mechanic.