Introduction: Diagnosis Lexus GX J120

FOR USING OBD-II SCAN TOOL OR HAND-HELD TESTER

1. Before using the scan tool or tester, the scan tool's instruction book or tester's operator manual should be read thoroughly.
2. If the scan tool or tester cannot communicate with the ECU controlled systems when you have connected the cable of the tester to the DLC3 with the ignition switch and tester turned ON, there is a problem on the vehicle side or tester side.

1. If the communication is normal when the tester is connected to another vehicle, inspect the diagnosis data link line (Bus (+) line) or ECU power circuit of the vehicle.
2. If the communication is still impossible when the tester is connected to another vehicle, the problem is probably in the tester itself, so perform the Self Test procedures outlined in the Tester Operator's Manual.

HOW TO PROCEED WITH TROUBLESHOOTING

HINT

Carry out troubleshooting in accordance with the procedures on the following reference. Here, only the basic procedures are shown. Details are provided in the Diagnostics section, 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 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 for DTCs according to the applicable table. OK: Go to step 5 . NG: Go to next step.
4. DTC table 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 table. Go to step 6 .
5. Problem Symptoms Table 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 does not recur, 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

Scheme 45

1. The diagnostic system in LEXUS GX470 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 form in the ECU memory. 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, it is possible to quickly narrow down potential problem areas and troubleshooting can be performed effectively. The diagnostic functions are incorporated in the following systems in LEXUS GX470.
2. In the DTC check, it is very important to determine whether the problem indicated by the DTC is still occurring or has occurred in the past but returned to normal at present. In addition during the problem symptom check it must be checked 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 symptom confirmation to determine the current conditions. If this is not done, it may, depending on the case, result in unnecessary troubleshooting for normally operating systems, making it more difficult to detect the problem area, or in trying to repair irrelevant areas. Therefore, always follow the procedures in the correct order and perform the DTC check.
3. A table showing how to proceed with troubleshooting using the diagnostic trouble code (DTC) check is (Scheme 46) This table shows how to utilize the DTC check effectively. Then, by carefully checking the results, this table indicates how to proceed either to the DTC troubleshooting or to the troubleshooting of the «PROBLEM SYMPTOMS TABLE»(ref-228746-S13698961862006041000000).

Scheme 46

Scheme 47

Scheme 48

1. DTC check Go to next step.
2. Make a note of DTCs displayed and then clear the memory Go to next step.
3. Symptom confirmation 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 A: Troubleshooting of problem indicated by DTC B: Go to next step.
6. Symptom confirmation 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-228746-S10052866652006041000000) ). 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 a secondary problem).

SYMPTOM SIMULATION

HINT

The most difficult case in troubleshooting is when no symptoms occurs. 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 when the engine is hot or when the vehicles is 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 stationary condition.

Important points in the symptom simulation test

In the symptom simulation test, the problem symptoms should be confirmed, and the problem area or parts must also be found out. To do so, reduce the possible problem circuits according to the symptoms before starting this test and have the hand-held tester connected 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 49

Scheme 50

Scheme 51

Scheme 52

1. VIBRATION METHOD: When vibration seems to be the major cause. PART AND SENSOR Apply slight vibration with your 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 and fulcrum of the vibration are the major areas to be checked thoroughly.
2. HEAT METHOD: If the problem seems to occur when the area in question 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 the components to more than 60°C (140°F) (Temperature is limited to keep the components from being damaged). Do not apply heat directly to the parts in the ECU.
3. WATER SPRINKLING METHOD: When the malfunction seems to occur on a rainy day or in high-humidity. 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 spraying a mist of water onto the radiator front surface. Never apply water directly onto the electronic components. HINT: If a vehicle is subject to water leakage, the leaking water may contaminate the ECU. When testing a vehicle with a water leakage problem, special caution must be taken.
4. OTHERS: If the malfunction seems to occur when electrical load is excessive. Turn on all the electrical equipment including the heater blower, headlights, rear window defogger, etc., and check if the malfunction occurs.

DIAGNOSTIC TROUBLE CODE TABLE

The inspection procedures are shown in the (Scheme 53) below. This table allows efficient and accurate troubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code table. Proceed with troubleshooting in accordance with the inspection procedures listed in the diagnostic table corresponding to the diagnostic trouble codes displayed. The diagnostic trouble code table for the Supplemental Restraint System is (Scheme 53)as an example.

Scheme 53

PROBLEM SYMPTOMS TABLE

The suspected circuits or parts for each problem symptom are shown in the (Scheme 54) below. Use this table to troubleshoot the problem when a Normal code is displayed in the diagnostic trouble code table but the problem is still occurring. Numbers in the table indicate the order in which the circuits or parts should be checked.

HINT

When the problem is not detected by the diagnostic system even though the problem symptom is present, it may be that the problem is occurring outside the detection range of the diagnostic system.

Scheme 54

CIRCUIT INSPECTION

How to read and use each reference is (Scheme 55)

Scheme 55

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Scheme 58

Scheme 59

Scheme 60

Scheme 61

Scheme 62

Scheme 63

Scheme 64

Scheme 65

Scheme 66

Scheme 67

Scheme 68

Scheme 69

1. BASIC INSPECTION RESISTANCE MEASURING CONDITION OF ELECTRONIC PARTS Unless stated, all resistance is measured at an ambient temperature of 68°F (20°C). Resistances measured may be outside the specifications if measured at high temperatures, i.e. immediately after the vehicle has been running. Measurements should be made after the engine has cooled down. HANDLING CONNECTORS When disconnecting a connector, first squeeze the mating halves tightly together to release the lock, then press the lock claw and separate the connector. When disconnecting a connector, do not pull on the harnesses. Grasp the connector directly and separate it. Before connecting the connector, check that there are no deformed, damaged, loose or missing terminals. When connecting a connector, press firmly until you hear the lock close with a "click" sound. If checking the connector with a TOYOTA electrical tester, check it from the backside (harness side) of the connector using a mini test lead. NOTE: As a waterproof connector cannot be checked from the backside, check by connecting a sub-harness. Do not damage the terminals by moving the inserted tester needle. CHECKING CONNECTORS Checking when the connector is connected: Squeeze the connector together to confirm that it is fully inserted and locked. Checking when the connector is disconnected: Check by pulling the wire harness lightly from the backside of the connector. Look for unlatched terminals, missing terminals, loose crimps or broken conductor wires. Check visually for corrosion, metallic or foreign objects and water; and bent, rusted, overheated, contaminated, and deformed terminals. NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal. Checking the contact pressure of the terminal: Prepare a spare male terminal. Insert it into a female terminal, and check for good tension when inserting and after full engagement. REPAIR METHOD OF CONNECTOR TERMINAL If there is any dirt on the terminal, clean the contact point using an air gun or shop rag. Never polish the contact point using a sandpaper as the platings may come off. If there is abnormal contact pressure, replace the female terminal. If the male terminal is gold-plated (gold color), use a gold-plated female terminal; if it is silver-plated (silver color), use a silver-plated female terminal. Damaged, deformed, or corroded terminals should be replaced. If the terminal will not lock into the housing, the housing may have to be replaced. HANDLING OF WIRE HARNESS If removing a wire harness, check the wiring and clamping before proceeding so that it can be restored in the same way. Never twist, pull or slacken the wire harness more than necessary. Never make the wire harness come into contact with a high temperature part, rotating, moving, vibrating or sharp-edged parts. Avoid panel edges, screw tips and similar sharp items. When installing parts, never pinch the wire harness. Never cut or break the cover of the wire harness. If it is cut or broken, replace it or securely repair it with vinyl tape.
2. CHECK OPEN CIRCUIT For an open circuit in the wire harness in (Scheme 61), perform a resistance check (step b ) or a voltage check (step c ). Check the resistance. Disconnect connectors A and C and measure the resistance between them. Resistance: Below 1 ohm HINT: Measure the resistance while lightly shaking the wire harness vertically and horizontally. see scheme 2: (Scheme 62) Between terminal 1 of connector A and terminal 1 of connector C --> 10 k ohm or higher Between terminal 2 of connector A and terminal 2 of connector C --> Below 1 ohm If your results match the examples above, an open circuit exists between terminal 1 of connector A and terminal 1 of connector C. Disconnect connector B and measure the resistance between the connectors. see scheme 3: (Scheme 63) Between terminal 1 of connector A and terminal 1 of connector B1 --> Below 1 ohm Between terminal 1 of connector B2 and terminal 1 of connector C --> 10 k ohm or higher If your results match the examples above, an open circuit exists 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 by conducting a voltage check. see scheme 4: (Scheme 64) 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. Example results: 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 If your results match the examples above, an open circuit exists 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 (Scheme 65), locate the section by conducting a resistance check with the body ground (below). Check the resistance 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: 10 k ohm or higher HINT: Measure the resistance while lightly shaking the wire harness vertically and horizontally. see scheme 6: (Scheme 66) Between terminal 1 of connector A and body ground --> Below 1 ohm Between terminal 2 of connector A and body ground --> 10 kohm or higher If your results match the examples above, a short circuit exists 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 the body ground, and terminal 1 of connector B2 and the body ground. see scheme 7: (Scheme 67) Between terminal 1 of connector A and body ground --> 10 kohm or higher Between terminal 1 of connector B2 and body ground --> Below 1 ohm If your results match the examples above, a short circuit exists 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 at the wire harness side with the connector connected to the ECU. When no measuring condition is specified, perform the inspection with the engine stopped and the ignition switch ON. Check that the connectors are fully seated. Check for loose, corroded or broken wires. First check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty. Replace the ECU with a normal functioning one and check if the symptoms occur. If the trouble symptoms stop, replace the ECU. Measure the resistance between the ECU ground terminal and body ground. Resistance: Below 1 ohm Disconnect the ECU connector. Check the ground terminals (on the ECU side and wire harness side) for evidence of bending, corrosion or foreign material. Lastly check the contact pressure of the female terminals.