How to Diagnose

The most important point in troubleshooting is to determine "Probable Causes". Once the probable causes are determined, parts to be checked can be limited to those associated with such probable causes. The determination of the probable causes must be based on a theory and be supported by facts and must not be based on intuition only.





TROUBLESHOOTING STEPS
If an attempt is made to solve a problem without going through correct steps for troubleshooting, the symptoms could become more complicated, resulting in failure to determine the causes correctly and making incorrect repairs. The four steps below should be followed in troubleshooting.
Observe the symptom carefully. Check if there are also other problems.
In determining the probable causes, it is necessary to study the wiring diagram to understand the circuit as a system. Knowledge of switches, relays and other parts is necessary for accurate analysis. The causes of similar problems in the past must be taken into account.
Troubleshooting is carried out by making step-by-step checks until the true cause is found.
After the problems are corrected, be sure to check that the system operates correctly. Also check that new problems have not been caused by the repair.

INFORMATION FOR DIAGNOSIS
This information contains the harness diagrams as well as the individual circuit drawings, operational explanations, and troubleshooting hints for each component. The information is presented in the following manner:
1. Connector diagrams show the connector positions, etc., on the actual vehicle as well as the harness path.
2. Circuit diagrams show the configuration of the circuit with all switches in their normal positions.
3. Operational explanations include circuit drawings of voltage flow when the switch is operated and how the component operates in reaction.
4. Troubleshooting hints include numerous examples of problems which might occur, traced backward in a common-sense manner to the origin of the trouble. Problems whose origins may not be found in this manner are pursued through the various system circuits.

NOTE: Components of MFI, ETACS, etc. with ECU do not include 3 and 4 above. For this information, refer to a relevant group which includes details of these components.





GENERAL ELECTRICAL SYSTEM CHECK
A circuit consists of the power supply, switch, relay, load, ground, etc. There are various methods to check a circuit including an overall check, voltage check, short-circuit check, and continuity check. Each of the methods briefly described below apply only to circuits similar to the illustration.

1. VOLTAGE CHECK
1. Ground one lead wire of the test light. If a voltmeter is used instead of the test light, ground the grounding side lead wire.
2. Connect the other lead wire of the test light to the power side terminal of the switch connector. The test light should come on or the voltmeter should indicate a voltage.
3. Then, connect the test light or voltmeter to the motor connector. The test light should not come on, or the voltmeter should indicate no voltage. When the switch is turned on in this state, the test light should come on, or the voltmeter should indicate a voltage, with motor starting to run.
4. The circuit illustrated here is normal. If there is any problem, such as the motor failing to run, check voltages beginning at the connector nearest to the motor until the faulty part is identified.





2. SHORT-CIRCUIT CHECK
Because the fuse has blown, it is probable that there is a short circuit. Follow the procedures below to narrow down the short-circuit location.

STEP 1. Remove the blown fuse and connect the lest light across the fuse terminals (Switch: OFF).
If the test light illuminates, go to Step 2.
If the test light does not illuminate, go to Step 3.

STEP 2. Short-circuit exists between the fuse block and the switch.
Repair the harness between the fuse block and the switch. Repeat step 1.

STEP 3. Switch ON the switch (The test light illuminates but the illumination light does not).

STEP 4. Disconnect the illumination light connector.
If the test light illuminates, go to Step 5.
If the test light does not illuminate, go to Step 6.




STEP 5. Short-circuit between the switch and the illumination light.




STEP 6. Short-circuit exists between the connector and the illumination light.




3. CONTINUITY CHECK
1. When the switch is in the "OFF" position, the self power test light should illuminate or the ohmmeter should read 0 ohm, only when the contact points of terminals 1 and 2 are connected.
2. When the switch is in the "ON" position, the self power test light should come on or the ohmmeter should read 0 ohm, only when the contact points of terminals 3 and 4 are connected.