Probable Causes:

Loose Engine Ground
Open E1 Circuit
Short In Injector Circuit Or Injector
Fuel Line Pressure (Leaking Injector)
Open Or Short In Oxygen Sensor Or Circuit
Open Or Short In Oxygen Sensor Or Circuit
Vacuum Sensor
Compression Pressure
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.