Q: 2007 S80 V8 "charging system failure" - new ACM and rebuilt (by xemodex) ECM and LIN bus waveform on Blu/Brn wire scopes fine

Hi and thanks for contacting YourMechanic. To test the alternator correctly you will need to full field the alternator. Get a Vat 40 or a Ferret 40 and hook it up to the battery and put the inductive pick up on the alternator wire with the arrow facing away from the alternator. Put the selector on the machine to charging and turn the knob until the voltage reads 9.6 volts. This will simulate that the battery is dead and make the alternator work. If the alternator is not working, then it needs to be replaced. If the alternator is working, then check the wiring to the battery and to the computer. If all of the wires are good, then check the pins on the computer for any burned or loose pins. If they are good, then the computer may need to be flashed or replaced. If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from YourMechanic, that can assist you with the charging system issue.