Sub-Oxygen Sensor

NOTE: Sub-oxygen sensor may be used only on California applications on some models. See OXYGEN SENSOR APPLICATION table.

Warm engine to normal operating temperature. Check Engine Control Module (ECM) for stored diagnostic trouble code(s). See RETRIEVING TROUBLE CODES in articles listed below:
- TESTS W/CODES - NON-TURBO
- TESTS W/CODES - TURBO
  If sub-oxygen sensor or circuit fails, a diagnostic trouble Code 27 will set in Engine Control Module (ECM) memory. Clear diagnostic trouble code if present. See CLEARING TROUBLE CODES in articles listed below:
  - TESTS W/CODES - NON-TURBO
  - TESTS W/CODES - TURBO
Drive vehicle between 50 and 62 MPH for at least 5 minutes in 4th or 5th gear (M/T) or Drive (A/T). DO NOT drive vehicle at speeds exceeding 62 MPH, or trouble code will be canceled.
Stop engine and turn ignition off. Repeat steps and note if diagnostic trouble Code 27 exists again. If trouble Code 27 exists again, check sub-oxygen sensor circuit for continuity, shorts or grounds. Replace sub-oxygen sensor if circuit is okay.