Inspect Water Temperature Switch
WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
Using a ohmmeter and thermometer, check continuity between terminals.
Standard:
No continuity at 48 °C (118.4 °F) or less
.
Continuity at more than 55 °C (131 °F)
.
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