Introduction: Diagnosis Toyota 4Runner IV

HOW TO PROCEED WITH TROUBLESHOOTING

Note. Carry out a troubleshooting in accordance with the procedures on the following page. 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
2. Customer problem analysis Ask the customer about the conditions and environment when the problem occurred.
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 : 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.
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.
7. Repair Repair the affected system or part in accordance with the instructions in step 6.
8. Confirmation test After completing repairs, confirm that the problem has been solved. (If the problem dose not reoccur, 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

Note. The diagnostic system in 4RUNNER 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 4RUNNER. 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. A flow chart showing how to proceed with troubleshooting using the diagnostic trouble code (DTC) check is shown on the this page. 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 the problem symptoms table.

Scheme 47

Scheme 48

Scheme 49

1. DTC check
2. Making a note of the DTCs displayed
3. Symptom confirmation a : Go to step 5 b : Go To Next Step
4. Simulation test using symptom simulation methods
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 page «ELECTRONIC CIRCUIT INSPECTION PROCEDURE»(ref-190050-S42441265552005091300000) ). 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

Note. The most difficult case in troubleshooting is that no problem 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 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 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, narrow down the possible problem circuits according to the symptoms before starting this test and have a 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 50

Scheme 51

Scheme 52

Scheme 53

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. NOTE: 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: When the problem seems to occur when the suspect area is heated. 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 in the ECU. Heat the component that is the possible cause of the malfunction with a hair dryer or similar object. Check if the malfunction occurs.
3. WATER SPRINKLING METHOD: When the malfunction seems to occur on a rainy day or in a high-humidity condition. CAUTION: 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. 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. Sprinkle water onto the vehicle and check if the malfunction occurs.
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.

DIAGNOSTIC TROUBLE CODE CHART

The inspection procedures are (Scheme 55)permits an efficient and accurate troubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code chart. Proceed with troubleshooting in accordance with the inspection procedures given in the diagnostic chart corresponding to the diagnostic trouble codes displayed. The Supplemental Restraint System diagnostic trouble code chart is (Scheme 55)as an example.

Scheme 54

PROBLEM SYMPTOMS TABLE

The suspected circuits or parts for each problem symptom are (Scheme 56) Use this table to troubleshoot the problem when a "Normal" code is displayed in the diagnostic trouble chart check but the problem is still occurring. Numbers in (Scheme 56) indicate the inspection order in which the circuits or parts should be checked.

Note. When the problem is not detected by the diagnostic system even though the problem symptom is present, it is considered that the problem is occurring outside the detection range of the diagnostic system, or that the problem is occurring in a system other than the diagnostic system.

Scheme 55

CIRCUIT INSPECTION

How to read and use each page is shown below.

Scheme 56

Scheme 57

Scheme 58

Scheme 59

Scheme 60

Scheme 61

Scheme 62

Scheme 63

Scheme 64

Scheme 65

Scheme 66

Scheme 67

Scheme 68

Scheme 69

Scheme 70

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 needle. CONNECTOR CHECKING POINTS Checking when the connector is connected: By holding the connector, check the inserted condition and locking efficiency (engaged condition). NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal. 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). 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 of abnormal contact pressure, replace the female terminal. At this time, if a male terminal is gold-plated (gold color), use gold-plated female terminals and if it is silver-plated (silver color), use silver-plated female terminals. HANDLING OF WIRE HARNESS In case of removing the wire harness, check the wiring and clamping condition before the work so as to is restore it correctly. Never twist, pull or slack off the wire harness more than necessary. Never make the wire harness come into 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 sandwich the wire harness between them. Never cut or break the cover of the wire harness. If it is cut or broken, replace 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 63), perform "(b) Check the continuity" or "(c) Check the voltage" to locate the section. Check the continuity. NOTE: Measure the resistance while lightly shaking the wire harness vertically and horizontally. Disconnect connectors "A" and "C" and measure the resistance between them. Resistance: 1 ohms or less In the case of (Scheme 64): 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 65): 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 by conducting a voltage check. (Scheme 66), 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 67), locate the 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 terminal 1 and 2 of connector "A" and the body ground. Resistance: 1 Mohms or higher NOTE: Measure the resistance while lightly shaking the wire harness vertically and horizontally. In the case of (Scheme 68): 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 the body ground, and terminal 1 of connector "B2" and the body ground. In the case of (Scheme 69): 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, perform 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 body ground. Resistance: 1 ohms 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.