Check For Intermittent Problems
CHECKING FOR INTERMITTENT PROBLEMSNOTICE: LEXUS hand-held tester ONLY-
- By putting the vehicle's Engine Control Module (ECM) in check mode, one 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 an intermittent problem.
- CLEAR DIAGNOSTIC TROUBLE CODES (DTC).
The following actions will erase the DTCs and freeze frame data:
- Operate the OBD II scan tool (complying with SAE J1978) or LEXUS hand-held tester to erase the codes.
- See the OBD II scan tool's instruction book for operating instructions.
- Disconnect the negative (-) terminal cable from the battery or remove the 15 amp "EFI" fuse.
NOTICE: If the LEXUS hand-held tester switches the ECM from normal mode to check mode or vice-versa, or if the ignition switch is turned from ON to ACC or OFF during check mode, the DTCs and freeze frame data will be erased.
- SET CHECK MODE.
- Refer to "How to Display and Read Diagnostic Trouble Codes".
- Displaying & Reading Trouble Codes
NOTICE:
- After canceling out the DTC in memory and setting the check mode. if the MIL does not go off after the engine is started, check thoroughly for faulty contact, etc., then try the check again.
- If the MIL still does not go off, check and replace the ECM.
- PERFORM A SIMULATION TEST.
- Using the symptom simulation methods, apply vibration to and pull lightly on the wire harness, connector or terminals in the circuit indicated by the malfunction code.
- In this test, if the MIL lights up, it indicates that the place where the wire harness, connector or terminals being pulled or vibrated has faulty contact.
- Check for loose connection, dirt on the terminals, poor fit or other problems and repair as necessary.
- 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 pulled-out connector terminal, etc.
HINTS:
- A wire rarely breaks in the middle of its length. Most cases occur at the connector. Therefore carefully check the connectors of sensors and actuators.
- Faulty contact could be due to rusting of the connector terminals, foreign materials entering terminal or a drop in the contact pressure between the male and female terminals of the connector. Simply disconnecting and reconnecting the connectors once change 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, the cause is considered to be in the wire harness or connectors.
- SHORT CIRCUIT:
- This could be due a short circuit between the wire harness and the body ground or 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 improperly.
- VISUAL CHECK AND CONTACT PRESSURE CHECK.
HINT: When testing a gold-plated female terminal, always use a gold-plated male terminal.
- Disconnect the connectors at both ends.
- Check for rust or foreign material, etc. in the terminals of the connectors.
- Check crimped portions for looseness or damage and check if the terminals are secured in the lock portion.
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.
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.
- If necessary, use mini test leads.
- For water resistant connectors which cannot be accessed from behind, take good care not to deform the connector terminals.