Initial Inspection and Diagnostic Overview

Self-diagnosis is in which the input signal from each sensor is monitored by the ECU and should any abnormality occur in the input signal, the abnormal item is memorized by the computer. There are 7 diagnostic items including a normal reading that can be confirmed using a suitable voltmeter.
Malfunction code diagnosis items are as follows:
1. Oxygen Sensor.
2. Ignition Pulse (engine speed sensor).
3. Air flow sensor.
4. Normal reading (1.6 and 2.6 L engines). Pressure sensor (1.8L) engines.
5. Throttle position sensor.
6. ISC motor position sensor.
7. Engine coolant temperature sensor.
Indications are made by deflection of the pointer of voltmeter. Connect a voltmeter to the connector for diagnosis and the following indication will be made:
1. When normal, a constant 12 volts are indicated.
2. When abnormal, indication alternates between 0 volts and 12 volts every .4 seconds. When there are two or more abnormal items, the lowest code will be displayed first, then each additional code in ascending order.
When checking or correcting engine component malfunctions, check basic engine components prior to troubleshooting diagnostic system.
Check power supply for:
1. Faulty battery.
2. Faulty fusible link.
3. Faulty fuse.
4. Check for faulty body ground.
Check Fuel supply for:
1. Damaged fuel line.
2. Clogged or damaged fuel filter.
3. Faulty fuel pump.
Check ignition system for:
1. Faulty spark plugs.
2. Faulty ignition wiring.
3. Faulty distributor.
4. Faulty ignition coil.
Check emission control system for:
1. Faulty PCV system.
2. Faulty EGR system.
3. Vacuum leak.
Also, check ignition timing and idle speed. ECI system faults are often caused by poor harness contact, therefore, check that connector is secure.