Check For Intermittent Problems

LEXUS HAND-HELD TESTER ONLY
By putting the vehicle's Engine Control Module (ECM) in Check Mode, 1 trip detection logic is possible instead of 2 trip detection logic and sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.

CLEAR DIAGNOSTIC TROUBLE CODES
Refer to "How to Clear Diagnostic Trouble Codes" under Computers and Control Systems / System Diagnosis.
Testing and Inspection

SET CHECK MODE
Refer to "How to Display and Read Diagnostic Trouble Codes" under Computers and Control Systems / System Diagnosis.
Testing and Inspection

PERFORM A SIMULATION TEST






Using the symptom simulation , shake and pull lightly on the wire harness, connector or terminals in the circuit indicated by the malfunction code. In this test, if the malfunction indicator lamp lights up, it indicates that the place where the wire harness, connector or terminals being pulled or shaken has faulty contact. Check that point for loose connections, dirt on the terminals, poor fit or other problems and repair as necessary.
HINT: After cancelling out the diagnostic trouble code in memory and setting the check mode, if the malfunction indicator lamp does not go off after the engine is started, check thoroughly for faulty contacts, etc., then try the check again. If the malfunction indicator lamp still does not go off, check and replace the ECM.

CONNECTOR CONNECTION AND TERMINAL INSPECTION
When checking for an open circuit or short circuit, it is important to check the connector connection and the condition of the terminals.

- OPEN CIRCUIT:



- This could be due to a disconnected wire harness, faulty contact in the connector, a connector terminal pulled out, etc.

HINTS:
- A wire rarely breaks in the middle of it's length. Most cases occur at the connector. In particular, carefully check the connectors of sensors and actuators.
- Faulty contact could be due to rusting of the connector terminals, to foreign materials entering the terminals or a drop in the contact pressure between the male and female terminals of the connector. Simply disconnecting and reconnecting the connectors once changes the condition of the connection and may result in a return to normal operation. Therefore, in troubleshooting, if no abnormality is found in the wire harness and connector check, but the problem disappears after the check, them the cause is considered to be in the wire harness or connectors.

- SHORT CIRCUIT:



- This could be due to a short circuit between the wire harness and the body ground or to a short inside the switch, etc.
HINT: When there is a short between the wire harness and body ground, check thoroughly whether the wire harness is caught in the body or is clamped properly.

VISUAL CHECK AND CONTACT PRESSURE CHECK
- Disconnect the connectors at both ends.
- Check for rust or foreign material, etc. on the terminals of the connectors.



- Check crimped portions for looseness or damage and check if the terminals are secured in the lock position.
HINT: The terminals should not come out when pulled lightly.




- Prepare a test male terminal and insert it in the female terminal, then pull it out.
NOTICE: When testing a gold-plated female terminal, always use a gold-plated male terminal.
HINT: When the test terminal is pulled out more easily than others, there may be poor contact in that section.

CONNECTOR HANDLING



When inserting tester probes into a connector, insert them from the rear of the connector. When necessary, use mini test leads. For water resistant connectors which cannot be accessed from behind, take good care not to deform the connector terminals.