Malfunction Indicator Lamp: Description and Operation

PURPOSE/OPERATION
As a functional test the malfunction indicator lamp illuminates at key-on before engine cranking. Whenever the powertrain control module sets a diagnostic trouble code that effects vehicle emissions, it illuminates the malfunction indicator lamp. The malfunction indicator lamp remains on until the diagnostic trouble code is erased. The malfunction indicator lamp either flashes or illuminates continuously when the powertrain control module detects active engine misfire. During active engine misfire the powertrain control module records the current engine operating conditions.








ITEMS INDICATED BY THE CHECK ENGINE/MALFUNCTION INDICATOR LAMP

NOTE:
1. After the power train control module detects a malfunction, the check engine/malfunction indicator lamp illuminates when the engine is next turned on and the same malfunction is re-detected.
However, for items marked with a "*", the check engine/malfunction indicator lamp illuminates on the first detection of the malfunction.
2. After the check engine/malfunction indicator lamp illuminates, it will be switched off under the following conditions.
- When the powertrain control module monitored the powertrain malfunction three times* and detected no malfunction.
*: In this case, one time indicates from engine start to stop.
- For misfiring or a fuel trim malfunction, when driving conditions (engine speed, engine coolant temperature, etc.) are similar to those when the malfunction was first recorded. In addition, the powertrain control module has detected no malfunction.

Caution: If the check engine/malfunction indicator lamp illuminates because of a malfunction of the powertrain control module, transmission between the scan tool and the powertrain control module cannot occur. In this case, the diagnostic trouble code cannot be read.