Testing & Diagnosis: Self-Diagnosis
The Self-Diagnosis system, an integral part of the computer (ECU), monitors all input signals from each sensor. If an abnormal input signal occurs, that item is memorized by the computer (ECU). There are 7 diagnostic codes (8 for Cordia/Tredia) including normal operating condition. See DIAGNOSTIC CODE table. They can be confirmed by using a voltmeter.
If 2 or more systems are non-functional, they are indicated in order of increasing code number. Indication is made by deflection of voltmeter pointer. A constant 12 volts indicates system is normal. If system is abnormal, voltmeter will alternate between 0 and 12 volts every 0.4 seconds. After indication of 0 volts for 2 seconds, the higher code is indicated. See Fig 1.
NOTE:
The ECU abnormal diagnostic memory is kept by direct power supply from the battery. Memory is not erased by turning off ignition switch but will be erased if back-up power supply is eliminated by disconnecting battery cable or ECU unit.
DIAGNOSTIC CODE
| Code Number | Diagnostic Item |
|---|---|
| 1 | Oxygen Sensor & Computer |
| 2 | Engine Speed Sensor |
| 3 | Airflow Sensor |
| 4 | Pressure Sensor (Cordia/Tredia only) |
| 5 | Throttle Position Sensor |
| 6 | ISC Motor Position Sensor |
| 7 | Coolant Temperature Sensor |