1. On the battery side of the vehicle there should be a green connector.
2. If the following conditions are met, short the test terminal with the ground terminal (pins 1 and 2 - see the figure below for reference)
NOTE: Make sure no other pins are shorted except those specified.
3. Set the ignition switch to ON, making sure not to start the engine.
4. Record the diagnostic codes that are flashed by the check engine light. There will be a series of flashes that are seperated by short off periods; the codes will be seperated by longer pauses. Keep reading until the codes repeat.
| Code No. | Diagnosis Item | Diagnosis Contents | Trouble Area |
| 1 | Normal | - | - |
| 2 | Pressure Sensor | When the input signal from the pressure sensor deviates from the specified value | Pressure sensor Pressure sensor circuit ECU |
| 3 | Ignition signal | When the ignition signal fails to be inputted | Distributor Ignitor Ignition coil Ignition system circuit ECU |
| 4 | Water temperature sensor | When the input signal from the water temperature sensor deviates from the specified value | Water temperature sensor Water temperature sensor circuit ECU |
| 5 | Oxygen sensor signal | When the input signal from the oygen sensor fails to be inputted under the certain conditions | Oxygen sensor Oxygen sensor circuit ECU |
| 7 | Throttle position sensor | When both idle switch and power switch enter"ON" conditions | Throttle position sensor Throttle position sensor circuit ECU |
| 8 | Intake air temperature sensor | When the input signal from the intake air temperature sensor deviates from the specified value | Intake air temperature sensor Intake air temperature sensor circuit ECU |
| 9 | Vehicle speed sensor | When the input signal from the vehicle speed sensor fails to be inputted under the certain conditions | Vehicle speed sensor Vehicle speed sensor circuit ECU |
| 10 | Starter signal | When the input signal from the starter fails to be inputted, until the certain conditions are satisfied:
However, it should be noted that this code may be memorized when the vehicle is started by being pushed. | Starter Starter circuit ECU |
| 11 | Switch signal | When even one even one of the following conditions is satisfied with the test terminal shorted with the ground terminal: when the airconditioner is funtioning. when the idle switch is turned OFF | Air conditioner circuit Throttle position sensor Throttle position sensor circuit ECU |
| 12 | EGR control system | When it is judged that the EGR control system is not functioning normally under the certain conditions | EGR valve Modulator EGR VSV Water temperature sensor |
| 15 | Air-to-fuel ratio (rich fail) | When the feedback function performs reduction compensation beyond the specified level | Injector circuit Injector Fuel Pressure Pressure regulator Pressure sensor Water temperature sensor Water temperature sensor circuit Intake air temperature sensor Intake air temperature sensor circuit |
| 16 | Air-to-fuel ratio (lean fail) | When the feedback function performs increase compensation below the specified level | Injector circuit Injector Fuel Pressure Pressure regulator Pressure sensor Water temperature sensor Water temperature sensor circuit Intake air temperature sensor Intake air temperature sensor circuit |
NOTE: if your check engine light doesn't flash, your diagnostic system may be having problems
