Oxygen Sensor: Testing and Inspection

Checking Oxygen Sensor

Preliminary condition:

Engine oil temperature at least 60°C (140°F)

Work sequence

- Connect CO meter to test receptacle on exhaust pipe (left side)





- With ignition turned OFF, disconnect connection 1 between oxygen sensor and control unit
- Pull off vacuum hose 2 from pressure regulator and block hose
- Start engine
CO must increase to above 1.5%


- After about 2 minutes reconnect connection 1
CO must drop to 0.7 ±0.4%

If NO, following components may be defective:
Wire between oxygen sensor and control unit or control unit

- Check wiring by disconnecting connection 1 again and ground wire end coming from control unit
CO must increase

If OK, oxygen sensor must be defective or leak in exhaust system between catalytic converter and cylinder head