2006 XC90 2.5 turbo. My battery light came on and car died. Replaced alternator and battery. Light still on. Getting the following codes. 1A66, 1A64 and 8F12. CEM checks out as good. Totally at a loss, suggestions?

 

Yes, you put a bad alternator on. What brand and where did you get your replacement alternator?

 

I changed the altenator twice. Not the problem. code 1a66 and 1a64 seem to be the problem. What are they?

 

Google brings up - 1a64 DEM communications, (Differential module) 1a66 is infotainment module, and 8f12 is headlight height control. Is the new alternator charging? Alternators used to be simple. 2 wires - 1 to the battery the other directly to the light bulb on the dash. Now some have a LIN bus connection. Two way communication between the voltage regulator and the CEM (on your car) And if the replacement alternator does not support that function - the cem won't know to turn the alternator light off. Diagram below. Or xemodex mentions LIN communication with the alternator is a common failure of the CEM. Common failures below courtesy of xemodex.