[CJMR2T]

Oh, grounding the W terminal is only a check to make sure that the circuit is good up to the ECU. It has nothing to do with the battery light.

Any time you turn on the key, the battery light should come on and then go out once the engine is started.... The battery light is actually a misrepresentation of what it really is as it is not representive of the battery but rather the alternator.... Most all alternators have whats called a "Light Circuit", its a sensory circuit that monitors the alternators output voltage and anytime the alternators output voltage is below about 11.5v it completes a ground in the circuit thus turning on the light.

Manufactures feel that its easier for people to understand a battery symble then a alternator symble thus the reason for it being a battery symble.

EDIT: Oh some alternators actually output a voltage to turn the light on instead of supplying a ground....