Diagnostic Strategies

TROUBLESHOOTING
When checking and correcting engine troubles, it is important to start with inspection of the basic Systems.
In case you have such troubles as (1) engine start failure, (2) unstable idling or (3) poor acceleration, therefore, you should first check the following basic systems:

(1) Power supply
- Battery
- Fusible link
- Fuse
(2) Body ground
(3) Fuel supply
- Fuel line
- Fuel filter
- Fuel pump
(4) Ignition system
- Spark plug
- High tension cable
- Distributor
- Ignition coil
(5) Emission control system
- PCV system
- EGR system
- Vacuum leak
(6) Others
- Ignition timing
- Idle speed

Troubles with the ECI system are often caused by poor contact of harness connector. It is, therefore, important to check harness connector contact.

SYSTEM TESTING PRECAUTIONS
(1) Before removing or installing a part, read diagnosis code and then disconnect the battery (-) terminal cable.
(2) Before disconnecting the cable from battery terminal, turn the ignition switch to OFF. Removal or connection of battery cable during engine operation or while the ignition switch is ON could cause erroneous operation to the ECU or damage to semiconductors.
(3) The control harnesses between the ECU and the ignition coil (-) terminal and oxygen sensor are shielded wires with shield grounded to the body in order to prevent influence of ignition noises and radio interference. When the shielded wire is faulty, therefore, the control harness must be replaced.
(4) When ECI checker is used, pay attention to the following:
- Avoid rough operation of switches.
- Do not subject ECI checker to shock and other external forces, heat, etc.
- Keep the checker away from water and oil.
- Store ECI checker in a moisture- and dust-free place and take steps to protect the checker from heat and vibration.

PRECAUTIONS FOR OPERATION
(1) When battery voltage is low, no detection of failure is possible. Be sure to check the battery for voltage and other conditions before starting the test.
(2) Diagnosis item is erased if the battery or the ECU connector is disconnected. Do not disconnect the battery before the diagnosis result is completely read.
(3) To diagnose the oxygen sensor, warm up engine and drive a good distance. Do not turn off the ignition switch after driving. If ignition switch is turned off, the result in memory is erased.
(4) After check and correction are over, disconnect ground cable for 10 seconds or more from negative terminal of battery and connect it again to make sure that failure code is erased.