California Models

DIAGNOSTIC PROCEDURE





1. Are there any other codes besides 21 or 28 being output?
- If Yes proceed to relevant Diagnostic Trouble Code chart.
- If No replace Main Heated Oxygen Sensor.

NOTE: If Diagnostic Trouble Code "21" is output inspect / replace front Main Oxygen Sensor. If Diagnostic Trouble Code "28" is output, inspect / replace rear Main Oxygen Sensor.