On-Vehicle Inspection

WARNING: This page is about a different car, the 2008 Toyota Yaris. However, it is still accessible from the selected car via links, so may be relevant.

INSPECT ENGINE OIL PRESSURE SWITCH ASSEMBLY
1. Disconnect the engine oil pressure switch connector.
2. Using an ohmmeter, check the resistance between the engine oil pressure switch terminal and body ground.
  Standard resistance (Engine stopped): Below 1 Ω
  
  Standard resistance (Engine idling): 10 kΩ or higher
  
  HINT:
  
  If the value is not as specified, replace the engine oil pressure switch assembly.