H13 - Check Secondary Air Injection Operation

NOTE: If vehicle is not equipped with Secondary Air Injection (AIR) or is equipped with Pulsed-Secondary Air Injection (PAIR), ignore this step and go to H14. H14 - Check HO2S Integrity

With dual Heated Oxygen Sensor (HO2S), Diagnostic Trouble Code (DTC) 172 refer to right or rear HO2S; DTC 136, 176 refers to left or front HO2S. HO2S always lean could be caused by:

- Thermactor air being diverted upstream from the HO2S.

- Key "OFF".

- Disconnect the AIR hose(s) from the AIR pump so that secondary air is bypassed to atmosphere during testing.

- Run Engine Running Self-Test. Key ON Engine Running (KOER) Self-Test

- Are DTCs 136, 172, 176 present?

Yes -- Reconnect AIR Hose. Go to H14. H14 - Check HO2S Integrity

No -- For Continuous Memory DTCs 139, 144, 171, 176, 177: Go to H90. H90 - Check Continuous Monitor Diagnostic Test Mode

All Others: Go to Emission Control Systems/Testing and Inspection for AIR systems diagnosis.