Introduction: Diagnosis Lexus SC II

HOW TO PROCEED WITH TROUBLESHOOTING

HINT

Carry out a troubleshooting in accordance with the procedures on the following: Here, only the basic procedures are shown. Details are provided in the Diagnostics information , showing the most effective methods for each circuit. Confirm the troubleshooting procedures first for the relevant circuit before beginning the troubleshooting of that circuit.

1. VEHICLE BROUGHT TO WORKSHOP : Go to Next Step
2. CUSTOMER PROBLEM ANALYSIS Ask the customer about the conditions and the environment when the problem occurred. : Go to Next Step
3. SYMPTOM CONFIRMATION AND DTC (AND FREEZE FRAME DATA) CHECK Check the battery positive voltage. Voltage: 10 - 14 V (Engine stopped) Visually check the wire harness, connectors and fuses for open and short, etc. Warm up the engine to the normal operating temperature. Confirm the problem symptoms and conditions, and check the DTCs according to the applicable chart. OK: Go to step 5 NG: Go To Next Step
4. DTC CHART Check the results obtained in step 3, then confirm the inspection procedures for the system or the part which should be checked using the DTC chart. Go to step 6
5. PROBLEM SYMPTOMS CHART Check the results obtained in step 3, then confirm the inspection procedures for the system or the part which should be checked using the problem symptoms table. : Go to Next Step
6. CIRCUIT INSPECTION OR PARTS INSPECTION Confirm the circuit for the system or the part which should be checked using the problem symptoms table or the results obtained in step 4. : Go to Next Step
7. REPAIR Repair the affected system or part in accordance with the instructions in step 6. : Go to Next Step
8. CONFIRMATION TEST After completing repairs, confirm that the problem has been solved. (If the problem is not reproduced, perform a confirmation test under the same conditions and in the same environment as when it occurred for the first time.) END

SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE

HINT

1. The diagnostic system in the LEXUS SC430 has various functions. The first function is the Diagnostic Trouble Code (DTC) Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory at the time of occurrence, to be output by a technician during troubleshooting. Another function is the Input Signal Check which checks if the signals from various switches are sent to the ECU correctly. By using these check functions, possible areas of the problem can be narrowed down quickly and troubleshooting can be performed effectively. The diagnostic functions are incorporated in the following systems in the LEXUS SC430. SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE System Diagnostic Trouble Code Check Input Signal Check (Sensor Check) Diagnostic Test Mode (Active Test) SFI System X (with Check Mode) X X Tire Pressure Warning System X ABS with EBD & BA & TRAC & VSC System X X X Electronically Controlled Automatic Transmission [ECT] X (with Check Mode) X Power Tilt and Power Telescopic Steering Column X Progressive Power Steering System X Air Conditioning System X X X Supplemental Restraint System X Lighting System X Audio System X LEXUS Navigation System X LEXUS Link System X Power Window Control System X Power Mirror Control System X Power Door Lock Control System X X Wireless Door Lock Control System X X Key Reminder Warning System X Engine Immobilizer System X Theft Deterrent System X X Retractive Hardtop System X X Multiplex Communication System X Cruise Control System X X
2. In the DTC check, it is very important to determine whether the problem indicated by the DTC is still occurring or occurred in the past but returned to normal at present. In addition, it must be checked in the problem symptom check whether the malfunction indicated by the DTC is directly related to the problem symptom or not. For this reason, the DTC should be checked before and after the symptom confirmation to determine the current conditions. If this is not done, it may, depending on the case, result in an unnecessary troubleshooting for normally operating systems, in making it more difficult to detect the problem area, or in repairing impertinences to the problem. Therefore always follow the procedures in the correct order and perform the DTC check.
3. A flow chart showing how to proceed with the troubleshooting using the diagnostic trouble code (DTC) check is shown in the following . This flow chart shows how to utilize the DTC check effectively. Then by carefully checking the results, this chart indicates how to proceed either to the DTC troubleshooting or to the troubleshooting of problem symptoms table.

1. DTC CHECK : Go to Next Step
2. MAKING A NOTE AND CLEARING OF THE DTCS DISPLAYED : Go to Next Step
3. SYMPTOM CONFIRMATION SYMPTOM CONFIRMATION a Problem symptoms exist b No problem symptoms exist a: Go to step 5 b: Go To Next Step
4. SIMULATION TEST USING THE SYMPTOM SIMULATION METHODS : Go to Next Step
5. DTC CHECK DTC CHECK a DTC displayed b Normal code displayed a: TROUBLESHOOTING OF PROBLEM INDICATED BY DTC b: Go To Next Step
6. SYMPTOM CONFIRMATION SYMPTOM CONFIRMATION a No problem symptoms exist b Problem symptoms exist If a DTC is displayed in the initial DTC check, it indicates that a trouble may have occurred in a wire harness or connector in that circuit in the past, therefore check the wire harness and connectors (See «ELECTRONIC CIRCUIT INSPECTION PROCEDURE»(ref-211244-S18044935542005121700000) ). a: SYSTEM NORMAL b: TROUBLESHOOTING OF EACH PROBLEM SYMPTOM The problem is still occurring in a place other than the diagnostic circuit (The DTC displayed first is either for a past problem or it is a secondary problem).

HINT

The most difficult case in troubleshooting is that there occurs no problem symptoms. In such cases, a thorough customer problem analysis must be carried out. Then simulate the same or similar conditions and environment in which the problem occurred in the customer's vehicle. No matter how much experience a technician has, or how skilled he may be, if he proceeds to troubleshoot without confirming the problem symptoms, he will tend to overlook something important in the repair operation and make a wrong guess somewhere, which will only lead to a standstill. For example, for a problem which only occurs when the engine is cold, or for a problem which occurs due to vibration caused by the road during driving, etc., the problem can never be determined so long as the symptoms are confirmed with the engine hot condition or the vehicle at a standstill. Since vibration, heat or water penetration (moisture) is a likely cause for the problem which is difficult to reproduce, the symptom simulation tests introduced here are effective measures in a point that the external causes are applied to the vehicle in a stopped condition.

Important points in the symptom simulation test

In the symptom simulation test, the problem symptoms should, of course, be confirmed, and the problem area or parts must also be found out. To do this, narrow down the possible problem circuits according to the symptoms before starting this test and connect a tester beforehand. After that, carry out the symptom simulation test, judging whether the circuit being tested is defective or normal and also confirming the problem symptoms at the same time. Refer to the problem symptoms table of each system to narrow down the possible causes of the symptom.

Scheme 33

Scheme 34

Scheme 35

Scheme 36

1. VIBRATION METHOD: When vibration seems to be the major cause. PART AND SENSOR Apply slight vibration with a finger to the part of the sensor considered to be the problem cause and check that the malfunction occurs. HINT: Applying strong vibration to relays may result in open relays. CONNECTORS Slightly shake the connector vertically and horizontally. WIRE HARNESS Slightly shake the wire harness vertically and horizontally. The connector joint, fulcrum of the vibration, and body through portion are the major areas to be checked thoroughly.
2. HEAT METHOD: When the problem seems to occur when the suspect area is heated. Heat the component that is the possible cause of the malfunction with a hair dryer or similar object. Check if the malfunction occurs. NOTE: Do not heat to more than 60°C (140°F) (Temperature is limited so as not to damage the components). Do not apply heat directly to the parts an the ECU.
3. WATER SPRINKLING METHOD: When the malfunction seems to occur on a rainy day or in a high-humidity condition. Sprinkle water onto the vehicle and check if the malfunction occurs. NOTE: Never sprinkle water directly onto the engine compartment, but indirectly change the temperature and humidity by applying water spray onto the radiator front surface. Never apply water directly onto the electronic components. HINT: If a vehicle is subject to water leakage, the leaked water may contaminate the ECU. When testing a vehicle with a water leakage problem, special caution must be taken.
4. OTHERS: When the malfunction seems to occur when electrical load is excessive. Turn on all the electrical loads including the heater blower, headlights, rear window defogger, etc., and check if the malfunction occurs.

Scheme 37

Scheme 38

Scheme 39

Scheme 40

Scheme 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

1. BASIC INSPECTION RESISTANCE MEASURING CONDITION OF ELECTRONIC PARTS Unless stated, all resistance is measured at an ambient temperature of 20°C (68°F). Because the resistance may be outside the specifications if measured at high temperatures immediately after the vehicle has been running, measurements should be made when the engine has cooled down. HANDLING OF CONNECTOR When removing the connector with a lock, press the connector toward the engagement and remove the lock by making the lock claw movable easily. When removing the connector, do not hold the harness, but hold the connector. Before connecting the connector, check that there are no deformation, damage and missing of the terminals. Connection of the connector with a lock should be securely done until it makes a click sound. In case of checking the connector with a Toyota electrical tester, perform it at the back side (harness side) of the connector using a mini test lead. NOTE: As a water proof connector cannot be checked from its back side, check by connecting the sub-harness. Do not damage the terminals by moving the inserted tester stick. CONNECTOR CHECKING POINTS Checking when the connector is connected: By holding the connector, check the inserted condition and locking efficiency (engaged condition). Checking when the connector is removed: Check by pulling the wire harness lightly (missing terminal, terminal crimping condition, core wire break). Check visually if there is any rust, metal tip, water and bend of terminal (rust, mixing of foreign object, terminal deformation). NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal. Checking of the contact pressure of the terminal: Prepare the same terminal as a male terminal. By inserting it to a female terminal, check the engaged condition and sliding load. REPAIR METHOD OF CONNECTOR TERMINAL In case that there is any soil at the contact point, clean the contact point using an air gun or shop rag. At this time, never polish the contact point using a sand paper as the platings may come off. In case that the contact pressure is abnormal, change the female terminal. At this time, if a male terminal of the counterpart of the part side is gold-plated (gold color), use gold-plated female terminals and if it is silver-plated (silver color), use silver-plated. HANDLING OF WIRE HARNESS In case of removing the wire harness, check the wiring and clamping condition before the work so as to restore it surely. Never twist, pull or slack off the wire harness more than necessary. Never make the wire harness have contact with a high-temperature part, rotating, moving, vibrating or acute-angled part (edge of the panel, tip of the screw, etc.). When installing parts, never let the wire harness be involved in them. Never break the cover of the wire harness. If it is broken, change it or securely repair it with a vinyl tape or the like.
2. CHECK OPEN CIRCUIT For the open circuit in the wire harness in (Scheme 42), perform "(b) Check the continuity" or "(c) Check the voltage" to locate the open section. Check the continuity. Disconnect connectors "A" and "C" and measure the resistance between them. Resistance: 1 ohm or less HINT: Measure the resistance while lightly shaking the wire harness vertically and horizontally. In the case of (Scheme 43): Between terminal 1 of connector "A" and terminal 1 of connector "C" --> No continuity (open) Between terminal 2 of connector "A" and terminal 2 of connector "C" --> Continuity Therefore, it is found out that there is an open circuit between terminal 1 of connector "A" and terminal 1 of connector "C". Disconnect connector "B" and measure the resistance between the connectors. In the case of (Scheme 44): Between terminal 1 of connector "A" and terminal 1 of connector "B1" --> Continuity Between terminal 1 of connector "B2" and terminal 1 of connector "C" --> No continuity (open) Therefore, it is found out that there is an open circuit between terminal 1 of connector "B2" and terminal 1 of connector "C". Check the voltage. In a circuit in which voltage is applied (to the ECU connector terminal), an open circuit can be checked for by conducting a voltage check. (Scheme 45), with each connector still connected, measure the voltage between the body ground and terminal 1 of connector "A" at the ECU 5 V output terminal, terminal 1 of connector "B", and terminal 1 of connector "C", in that order. If the results are: 5 V: Between terminal 1 of connector "A" and body ground 5 V: Between terminal 1 of connector "B" and body ground 0 V: Between terminal 1 of connector "C" and body ground Then it is found out that there is an open circuit in the wire harness between terminal 1 of "B" and terminal 1 of "C".
3. CHECK SHORT CIRCUIT If the wire harness is ground shorted as in (Scheme 46), locate the shorted section by conducting a "continuity check with the body ground". Check the continuity with the body ground. Disconnect connectors "A" and "C" and measure the resistance between terminals 1 and 2 of connector "A" and the body ground. Resistance: 1 Mohm or higher HINT: Measure the resistance while lightly shaking the wire harness vertically and horizontally. In the case of (Scheme 47): Between terminal 1 of connector "A" and body ground --> Continuity (short) Between terminal 2 of connector "A" and body ground --> No continuity Therefore, it is found out that there is a short circuit between terminal 1 of connector "A" and terminal 1 of connector "C". Disconnect connector "B" and measure the resistance between terminal 1 of connector "A" and body ground, and terminal 1 of connector "B2" and body ground. In the case of (Scheme 48): Between terminal 1 of connector "A" and body ground --> No continuity Between terminal 1 of connector "B2" and body ground --> Continuity (short) Therefore, it is found out that there is a short circuit between terminal 1 of connector "B2" and terminal 1 of connector "C".
4. CHECK AND REPLACE ECU NOTE: Start an inspection of the connector from the backside of the connector on the wire harness side with the connector connected to the ECU. When no measuring condition is specified, make the inspection with the engine stopped and also the ignition switched ON. First check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty. So replace the ECU with a normal functioning one and check if the symptoms appear. Measure the resistance between the ECU ground terminal and the body ground. Resistance: 1 ohm or less Disconnect the ECU connector, check the ground terminals on the ECU side and wire harness side for bend and check the contact pressure.