Self-Diagnostic System: Pre-Check
WARNING: This page is about a different car, the 2003 Lexus IS 300 and 2002 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.
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Diagnostic System
- Each ECU of this vehicle is connected by the communication bus and it transmits each signal by communication. This communication bus is self-diagnosed by the body ECU and it memorizes the DTC when it detects communication stop to the ECU or communication bus +B short or GND short. There is a possibility that the body ECU cannot self-diagnose accurately unless it doesn't work normal. Trouble shooting of the body electrical system should be done after confirming if the body ECU and open door indicator light works normal by the Basic Inspection (Check Body ECU Operation). See step 2.
- If the DTC of the ECU communication stop is output, there is a possibility of the connector disconnection or 2 communication buses open. See Fig 1. It will not become abnormal with only 1 communication bus open.
- If 2 communication buses are open at the position, DTC of the ECU communication stop between those 2 buses is output. See Fig 2.
- Basic Inspection (Check Body ECU Operation) - Inspect the body ECU operation. With this inspection , the body ECU can be diagnosed if it works normal or not. Check if the luggage compartment door opener works normal. If the results are OK, go to step 3. If the results are not good, check the luggage compartment door opener system (except body ECU). See POWER DOOR LOCKS & TRUNK LID article. If the results are OK, replace the faulty body ECU located behind the left kick panel. If the results are not good, repair or replace the malfunction part.
- Open Door Indicator Light Inspection - Check if the open door indicator light (located on the combination meter) is turned on when either door is open. If the open door indicator light is not turned on, DTC will not be output. If the results are OK, go to USING INDICATOR LIGHT under RETRIEVING DIAGNOSTIC TROUBLE CODES. If the results are not good, repair the open door indicator light. See INSTRUMENT PANEL article.