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Oxygen Sensor Relay: Testing and Inspection

Normally-open type A:

Check for continuity between the terminals.
- There should be continuity between the No.1 and No. 2 terminals when power and ground are connected to the No.3 and No. 4 terminals.
- There should be no continuity between the No.1 and No.2 terminals when power is disconnected.

Heated oxygen sensor relay (California)