- Precautions In Diagnosing Faults

The ``Check Engine'' light will illuminate only if the malfunction(s) which exist apply to one or more of the trouble codes. It will take the light at least five seconds to go on after the malfunction occurs. If the problem corrects itself, the light will go out, but the code(s) will be stored in the ECM. A Code 12 will not be stored in the memory. If the light comes on intermittently, but no codes are stored, refer to ``Erratic or Intermittent Check Engine Light.'' Any stored codes will be cleared if the problem does not reoccur within fifty engine starts. After performing any trouble code test, confirm ``Closed Loop'' operation as described under ``Trouble Code Test Lead'' and ensure ``Check Engine'' light is not illuminated.