### Self-Diagnostic System

#### DIAGNOSIS AND TESTING

The self-diagnostic function is useful for diagnosing malfunctions in major sensors and actuators of the ECCS system. There are 5 modes in self-diagnostics on all models except Stanza. On Stanza, there are 2 modes in self-diagnostics

##### Mode 1

###### EXCEPT STANZA

During closed loop operation, the green inspection lamp turns ON when a lean condition is detected and OFF when a rich condition is detected. During open loop operation, the red inspection lamp stays OFF.

###### STANZA

During this mode, the red LED in the ECU and the CHECK ENGINE LIGHT on the instrument panel stay ON. If either remain OFF, check the bulb in the CHECK ENGINE LIGHT or the red LED.

##### Mode 2

###### EXCEPT STANZA

The green inspection lamp function is the same as in Mode 1. During closed loop operation, the red inspection lamp turns ON and OFF simultaneously with the green inspection lamp when the mixture ratio is controlled within the specified value. During open loop operation, the red inspection lamp stays OFF.

###### STANZA

This models uses Mode 2 for self-diagnostic results and exhaust gas sensor monitor.

When in Mode 2 (self-diagnostic results), a malfunction code is indicated by the number of flashes from the red LED or the CHECK ENGINE LIGHT.

When in Mode 2 (exhaust gas sensor monitor), the CHECK ENGINE LIGHT and red LED display the condition of the fuel mixture (rich/lean) which is monitored by the exhaust gas sensor. If 2 exhaust sensors are used (right side and left side), the left exhaust gas sensor monitor operates first, when selecting this mode.

##### Mode 3

This mode is the same as the former self-diagnosis mode.

##### Mode 4

During this mode, the inspection lamps monitor the ON/OFF condition of the idle switch, starter switch and vehicle speed sensor.

In switches ON/OFF diagnosis system, ON/OFF operation of the following switches can be detected continuously:

- Idle switch
- Starter switch
- Vehicle speed sensor

1. Idle switch and starter switch–the switches ON/OFF status at the point when Mode IV is selected is stored in ECU memory. When either switch is turned from ON to OFF or OFF to ON, the red LED on ECU alternately comes on and goes off each time switching is detected.
2. Vehicle speed sensor–The switches ON/OFF status at the point when Mode IV is selected is stored in ECU memory. When vehicle speed is 12 mph (20 km/h) or slower, the green LED on ECU is off. When vehicle speed exceeds 12 mph (20 km/h), the green LED on ECU comes ON.

##### Mode 5

The moment a malfunction is detected, the display will be presented immediately by flashing the inspection lamps during the driving test.

In real time diagnosis, if any of the following items are judged to be faulty, a malfunction is indicated immediately:

- Crank angle sensor
- Ignition signal
- Air flow meter output signal
- Fuel pump (some models)

Consequently, this diagnosis is a very effective measure to diagnose whether the above systems cause the malfunction or not, during driving test. Compared with self-diagnosis, real time diagnosis is very sensitive, and can detect malfunctioning conditions in a moment. Further, items regarded to be malfunctions in this diagnosis are not stored in ECU memory.

To switch the modes, turn the ignition switch ON, then turn the diagnostic mode selector on the control unit fully clockwise and wait for the inspection lamps to flash. Count the number of flashes until the inspection lamps have flashed the number of the desired mode, then immediately turn the diagnostic mode selector fully counterclockwise.

NOTE: When the ignition switch is turned OFF during diagnosis in each mode, and then turned back on again after the power to the control unit has dropped off completely, the diagnosis will automatically return to Mode 1.

The stored memory will be lost if the battery terminal is disconnected, or Mode 4 is selected after selecting Mode 3. However, if the diagnostic mode selector is kept turned fully clockwise, it will continue to change in the order of Mode 1, 2, 3, etc., and in this case, the stored memory will not be erased.

In Mode 3, the control unit constantly monitors the function of sensors and actuators regardless of ignition key position. If a malfunction occurs, the information is stored in the control unit and can be retrieved from the memory by turning ON the diagnostic mode selector on the side of the control unit. When activated, the malfunction is indicated by flashing a red and green LED (also located on the control unit). Since all the self-diagnostic results are stored in the control unit memory, even intermittent malfunctions can be diagnosed. A malfunctioning part's group is indicated by the number of both red and green LED's flashing. First, the red LED flashes and the green flashes follow. The red LED refers to the number of tens, while the green refers to the number of units. If the red LED flashes twice and the green LED flashes once, a Code 21 is being displayed. All malfunctions are classified by their trouble code number.

The diagnostic result is retained in the control unit memory until the starter is operated 50 times after a diagnostic item is judged to be malfunctioning. The diagnostic result will then be canceled automatically. If a diagnostic item which has been judged malfunctioning and stored in memory is again judged to be malfunctioning before the starter is operated 50 times, the second result will replace the previous one and stored in the memory until the starter is operated 50 more times.

In Mode 5 (real time diagnosis), if the crank angle sensor, ignition signal or air flow meter output signal are judged to be malfunctioning, the malfunction will be indicated immediately. This diagnosis is very effective for determining whether these systems are causing a malfunction during the driving test. Compared with self-diagnosis, real time diagnosis is very sensitive and can detect malfunctioning conditions immediately. However, malfunctioning items in this diagnosis mode are not stored in memory.