There are a few different things that can set the Charging System Failure message. First, check the Serpentine Belt and make sure it is tight and that it is not slipping around the pulleys. Inspect the belt for any signs of wear like an excessively shiny flat side or excessive cracks on the ribbed side. If there are any doubts, replace the belt. If the belt seems loose, then the Tensioner will need to be replaced.
If the belt looks in good shape and is tight, then the Battery and Alternator will need to be tested. There is a quick easy test for this, with the use of a voltage meter. With the engine running, take a voltage reading at the battery terminals. If the voltage is not between 13.2-14.4v, or fluctuates in and out of this area, the Alternator will need to be replaced. If the Alternator passes this test, turn the engine off and wait 15min. Take another reading at the battery terminals, this time with the engine off. If the voltage is anything less than 12v, the battery may have a "bad cell" and is not accepting the alternator's charge. If you do not have access to a voltage meter, most local "big chain" parts stores, like AutoZone, will run these tests for Free right in their parking lot. Make sure to also check the battery cables to make sure they are tight, making a good connection and are free of any corrosion at this time.
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