If the onewire circuit does not work, the charger will only output limited power to the board, and nothing will work off of the charger. The onewire circuit depends on proper function of the battery charger chip, the SMC, and the two ICs that are utilized in the onewire lines.

Common issues with the onewire circuit are the small, easily burned out vias to the U6901 logic gate that is powered by PP3V42_G3H, and corrosion under the SMC.

See more about the onewire circuit here.