There is no reset for the oil pressure light. Locate the single-wire oil pressure switch, usually near the oil filter. With the key on, disconnect the wire and note the light, then ground the wire and note the light. If the light goes out during one of those tests, replace the pressure switch.
A 2001 Toyota Previa owner changed the oil, but the oil light stayed on and asked how to reset it. Another user suggested disconnecting the battery, a bad sensor, or a free code check. The Toyota expert explained that the light is controlled by a pressure switch that comes on below about 7 psi, that there is no reset, and that the switch should be tested by disconnecting and grounding its wire. If the light goes out, the pressure switch should be replaced.
