HB11 - Check HO2S On Engines With MAF Sensor

NOTE: The purpose of this test is to verify the Heated Oxygen Sensor (HO2S) can generate greater than 0.5 volt during Key On Engine Running (KOER) Self-Test.

Any vacuum/air leaks in non-Electronic Engine Controls (EEC) areas could also cause DTC 136, 172 or 176. Check for:

- Leaking vacuum actuator (e.g. A/C control motor).

- Engine sealing.

- Exhaust Gas Recirculation (EGR) system.

- Positive Crankcase Ventilation (PCV) system.

- Unmetered air leak between Mass Air Flow (MAF) sensor and throttle body.

- Lead contaminated HO2S.

- Key "OFF".

- Disconnect appropriate HO2S sensor from vehicle harness.

- Connect Digital Volt/Ohm Meter (DVOM) to HO2S circuit and HO2S SIG RTN or HO2S GND at the HO2S connector.

- DVOM on 20 volt scale.

- Run engine at approximately 2000 rpm for two minutes.

- Rerun KOER Self-Test and monitor HO2S voltage. Key ON Engine Running (KOER) Self-Test

- Does DVOM indicate greater than 0.5 volt at the end of Self-Test?

Yes -- Go to HB12. HB12 - Check Continuity of HO2S and HO2S Ground

No -- Replace HO2S. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)