With Scan Tool

Fig. 2 Self-diagnosis checker tool.:

System malfunctions detected and stored in the emission control unit can be displayed using the self-diagnosis checker (tool No. 40 H018 9A1), Fig. 2.

Fig. 3 Self-diagnosis system trouble codes.:

Any current or memorized malfunctions are indicated by a displayed code number and a corresponding buzzer, Fig. 3. A monitor lamp on the checker indicates oxygen sensor operation. A normal air/fuel ratio is indicated by a continuous flashing of the lamp. The lamp will light continuously if the air/fuel mixture is lean and will not light at all if the mixture is rich.
If more than one malfunction is detected by the control unit, the numbers will be displayed in numerical order. When all stored codes are displayed, the sequence will repeat itself. The emission control unit memory can be erased by disconnecting the battery ground cable for approximately five seconds. The control unit has a fail-safe mechanism for main input sensors which will substitute values to allow vehicle operation under certain malfunction conditions.