Here in Mexico, a cousin’s son had problems with his 1993 Ranger. The CEL came on, and the battery meter dropped to zero. We discussed it, and I told them we should first read the code before he bothered to work on the alternator.
We messed around for a while, until we figured STI jack is shoved in a box with the EEC triangle jack. Grounding STI we counted blinks, and got 519, which is problems with Pressure Switch on the power steering pump. So, I told them lets work on the alternator.
I checked the leads to the alternator, and the field voltage came on when the switch was on, and the high current lead had full battery voltage on it.
He had to drive two hours to sell squash, so he took two fully charged batteries.
On the way home, he stopped at an electrical repair place. They found a bad armature, I think it’s called, the part that spins. Fixed that problem, and the CEL went back out.
So, I am guessing low voltage might cause some code failures?
Anyway, he was glad it was fixed.