Oxygen Sensor: Testing and Inspection

Checking Oxygen Sensor, (Calif. only)

Note: Oxygen sensor is located in exhaust system (in front of catalytic converter). It produces varying voltages (up to 1 volt) dependent on oxygen content of exhaust gases. These voltages are sent to electronic control unit which alter injection time accordingly. Oxygen sensor operates at all engine speeds, except warm-up. During full throttle enrichment the oxygen sensor signal is not used.

Preconditions:

Engine oil temperature at least 60°C (140°F)
Air temperature 20°C (68°F). Before starting following test procedures, wait until intake air sensor housing has assumed room temperature

Work sequence

- Connect tachometer according to manufacturer's instructions
- Connect CO meter to test receptacle in front of converter (do not connect at tailpipe)
- Check idle speed and adjust if necessary
850 - 950 rpm





- Disconnect oxygen sensor wire 1 to control unit
- Check CO %
0.7 ±0.4%

- Let engine idle, disconnect vacuum hose 2 at pressure regulator 3 and plug hose
CO% must increase to approx. 2.5%

- Reconnect oxygen sensor wire 1
C0 must drop to 0.7 ±0.4% if oxygen sensor is OK

If NO, following components may be defective:
Oxygen sensor
Wire between oxygen sensor and control unit
Leak in exhaust system between catalytic converter and cylinder head


Checking The Wire Between Oxygen Sensor And Control Unit





- Connect ohmmeter between oxygen sensor and terminal 24 on control unit
0 ohm, sensor wiring OK
Infinite ohm, sensor wiring defective