Probable Causes:

Loose Engine Ground
Open E1 Circuit
Open Injector Circuit
Fuel Line Pressure (Blocked Injector)
Open Or Short In Oxygen Sensor Or Circuit
Ignition System
Coolant Temperature Sensor
Vacuum Sensor
EGR System
ECU

NOTE: For oxygen sensor or circuit testing, see CODE 21 - OXYGEN SENSOR SIGNAL test procedures in this article. For injector or circuit testing, see TEST NO. 9.

NOTE: Diagnostic chart is not available from manufacturer.