I have a 97 jeep tj, 2.5L.
It was running great, parked it to run in the house for a few minutes, went and started it up and, everything was normal, then all the sudden the battery volt meter dropped to 9 and the check gauge light came on.
I did a code read out by turning the key three times and got 12-47-55.
Code 47 -Battery voltage sense input below target charging during engine operation. Also, no significant change detected in battery voltage during active test of generator output circuit.
It still fires up on first crank, but the volt meter now reads 12, then about 2 minutes later it drops back to 9 or lower and the check gauge light comes on,