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 8 diagnostic codes 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 by order of increasing code number. Indication is made by deflection of voltmeter pointer. A constant repetition of 12 volts at .5 second intervals with 1.5 seconds in between indicates system is normal. If system is abnormal, voltmeter will alternate between 0 and 12 volts.
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 |
| 2 | Crankshaft Angle Sensor |
| 3 | Airflow Sensor |
| 4 | Atmospheric Pressure Sensor |
| 5 | Throttle Position Sensor |
| 6 | Motor Position Sensor |
| 7 | Coolant Temperature Sensor |
| 8 | No. 1 Cylinder TDC Sensor |