A little while ago my battery bracket loosened up during a car limits day, and the leads disconnected from the mains. I guess this short trip broke my alternator diodes. It could have been much worse, driving without a connected car battery can lead to serious damage of electric component like the ECU as current and voltage peaks aren’t shaved by the connected battery.
Suddenly the battery indicator on the dash activated and my OBD reader showed 11.5V only (measured 12V on the battery itself). With a driven alternator is should be 13.5 – 14.0V
After excluding failure of the sense fuse R3 and exchanging the odyssey battery with the original spare the failure was allocated to the alternator itself.
Here’s how to replace the denso alternator on the 2zz-ge toyota engine in the 2004 Elise.