Introduction: Diagnosis Scion tC I

HOW TO PROCEED WITH TROUBLESHOOTING

HINT

Perform troubleshooting in accordance with the procedures below. The following is an outline of basic troubleshooting procedures. Details in the Diagnostics articles show the most effective methods for each circuit. Confirm the troubleshooting procedures for the circuit you are working on before beginning troubleshooting.

1. VEHICLE BROUGHT TO WORKSHOP NEXT: Go to next step
2. CUSTOMER PROBLEM ANALYSIS Ask the customer about the conditions and environment when the problem occurred. NEXT: Go to next step
3. SYMPTOM CONFIRMATION AND DTC (AND FREEZE FRAME DATA) CHECK Measure the battery positive voltage. Standard: 11 to 14 V (Engine stopped) Visually check the wire harness, connectors and fuses for open and short circuits. Warm up the engine to the normal operating temperature. Confirm the problem symptoms and conditions, and check for DTCs. Result: RESULT SPECIFICATION Result Proceed to DTC is output B DTC is not output A A: Go to step 5 B: Go to next step
4. DTC CHART Reconfirm the results obtained in step 3 . Then confirm the inspection procedures for the system or part using the DTC chart. NEXT: Go to step 6
5. PROBLEM SYMPTOMS CHART Reconfirm the results obtained in step 3 . Then confirm the inspection procedures for the system or part using the problem symptoms table. NEXT: Go to next step
6. CIRCUIT INSPECTION OR PARTS INSPECTION Confirm that the circuit or part is the cause of the malfunction. NEXT: Go to next step
7. REPAIR Repair the affected system or part according to the circuit or parts inspection. NEXT: Go to next step
8. CONFIRMATION TEST After completing repairs, confirm that the malfunction no longer exists. If the malfunction does not reoccur, perform a confirmation test under the same conditions and in the same environment as when it occurred the first time. NEXT: END

SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE

HINT

The diagnostic system in the SCION TC has various functions.

1. The first function is the Diagnostic Trouble Code (DTC) check. A DTC is a code stored in the ECU memory whenever a malfunction in the signal circuits to the ECU occurs. In a DTC check, a previous malfunction's DTC can be checked by a technician during troubleshooting.
2. Another function is the Input Signal Check, which checks if the signals from various switches are sent to the ECU correctly. By using these functions, the problem areas can be narrowed down and troubleshooting is more effective. Diagnostic functions are incorporated in the following systems in the SCION TC

Scheme 32

1. In the DTC check, it is very important to determine whether the problem indicated by the DTC is either: 1) still occurring, or 2) occurred in the past but has since returned to normal. In addition, the DTC should be compared to the problem symptom to see if they are related. For this reason, DTCs should be checked before and after confirmation of symptoms (i.e., whether or not problem symptoms exist) to determine current system conditions, as shown in the flowchart below. Never skip the DTC check. Failing to check DTCs may, depending on the case, result in unnecessary troubleshooting for systems operating normally or lead to repairs not pertinent to the problem.
2. A flowchart showing how to proceed with troubleshooting using the DTC check is shown below. Directions from the flowchart will indicate how to proceed either to DTC troubleshooting or to the troubleshooting of each problem symptom.

1. DTC CHECK NEXT: Go to next step
2. MAKE A NOTE OF DTCS DISPLAYED AND THEN CLEAR MEMORY NEXT: Go to next step
3. SYMPTOM CONFIRMATION Result: SYMPTOM CONFIRMATION RESULT Result Proceed to No symptoms exist A Symptoms exist B B: Go to step 5 A: Go to next step
4. SIMULATION TEST USING SYMPTOM SIMULATION METHODS NEXT: Go to next step
5. DTC CHECK Result: DTC CHECK RESULT Result Proceed to DTC is not output A DTC is output B B: TROUBLESHOOTING OF PROBLEM INDICATED BY DTC A: Go to next step
6. SYMPTOM CONFIRMATION Result: SYMPTOM CONFIRMATION RESULT Result Proceed to No symptoms exist A Symptoms exist B If a DTC was displayed in the initial DTC check, the problem may have occurred in a wire harness or connector in that circuit in the past. Check the wire harness and connectors (See «ELECTRONIC CIRCUIT INSPECTION PROCEDURE»(ref-224750-S28128780772006031100000) ). B: SYSTEM NORMAL A: 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 problem symptoms occur. In such cases, a thorough customer problem analysis must be carried out. A simulation of the same or similar conditions and environment in which the problem occurred in the customer's vehicle should be carried out. No matter how much skill or experience a technician has, troubleshooting without confirming the problem symptoms will lead to important repairs being overlooked and mistakes or delays.

For example

With a problem that only occurs when the engine is cold or occurs as a result of vibration caused by the road during driving, the problem can never be determined if the symptoms are being checked on a stationary vehicle or a vehicle with a warmed-up engine.

Vibration, heat or water penetration (moisture) is difficult to reproduce. The symptom simulation tests below are effective substitutes for the conditions and can be applied on a stationary vehicle.

Important points in the symptom simulation test

In the symptom simulation test, the problem symptoms as well as the problem area or parts must be confirmed. First, narrow down the possible problem circuits according to the symptoms. Then, connect the tester and carry out the symptom simulation test, judging whether the circuit being tested is defective or normal. Also, confirm the problem symptoms at the same time. Refer to the problem symptoms table for each system to narrow down the possible causes.

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 cause of the problem and check whether or not the malfunction occurs. HINT: Applying strong vibration to relays may 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 that should 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 device. Check if the malfunction occurs. NOTE: Do not heat to more than 60°C (140°F). Exceeding this temperature may damage components. 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. HINT: If the vehicle has or had a water leakage problem, the leakage may have damaged the ECU or connections. Look for evidence of corrosion or short circuits. Proceed with caution during water tests. NOTE: Never sprinkle water directly into the engine compartment. Indirectly change the temperature and humidity by applying water spray onto the front of the radiator. Never apply water directly onto the electronic components.
4. HIGH ELECTRICAL LOAD METHOD: When a malfunction seems to occur when electrical load is excessive Turn on the heater blower, headlamps, rear window defogger and all other electrical loads. Check if the malfunction reoccurs.

DIAGNOSTIC TROUBLE CODE CHART

Use Diagnostic Trouble Codes (DTCs) (from the DTC checks) in the table below to determine the trouble area and proper inspection procedure. The Supplemental Restraint System (SRS) DTC chart is shown below as an example.

Scheme 37

PROBLEM SYMPTOMS TABLE

The suspected circuits or parts for each problem symptom are shown in the table below. Use this table to troubleshoot when, during a DTC check, a "Normal" code is displayed but the problem is still occurring. Numbers in the table show the inspection order in which the circuits or parts should be checked.

HINT

In some cases, the problem is not detected by the diagnostic system even though a problem symptom is present. It is possible that the problem is occurring outside the detection range of the diagnostic system, or that the problem is occurring in a completely different system.

Scheme 38

CIRCUIT INSPECTION

How perform circuit inspection.

Scheme 39

Scheme 40

Scheme 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

Scheme 51

Scheme 52

Scheme 53

1. BASIC INSPECTION WHEN MEASURING RESISTANCE OF ELECTRONIC PARTS Unless stated, all resistance measurements should be made at an ambient temperature of 20°C (68°F). Resistance measurements may be inaccurate if measured at a high temperature, 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, and 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 a 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 a connector with a TOYOTA electrical tester, check the connector from the backside (harness side) 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 a connector is connected: Squeeze the connector to confirm that it is fully connected and locked. Checking when a 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. Visually check the connector for any of the following: Corrosion or water Metallic matter or other foreign matter Rust, damage from overheating, contamination or deformation Checking the contact pressure of the terminal: Prepare a spare male terminal. Insert it into a female terminal, and check for ample tension when inserting and after full engagement. NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal. REPAIR METHOD OF CONNECTOR TERMINALS If there is any dirt on the terminal, clean the contact point using an air gun or cloth. Never rub the contact point using sandpaper as the plating 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 HARNESSES 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. The wire harness should never come into contact with a high temperature part, or rotating, moving, vibrating or sharp-edged parts. Avoid contact with panel edges, screw tips and other 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 FOR OPEN CIRCUITS For an open circuit in the wire harness in (Scheme 45), 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. Standard (Scheme 46): TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition Connector A terminal 1 -Connector C terminal 1 10 kohm or higher Connector A terminal 2 -Connector C terminal 2 Below 1 ohm HINT: Measure the resistance while lightly shaking the wire harness vertically and horizontally. 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. Standard (Scheme 47): TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition Connector A terminal 1 -Connector B1 terminal 1 Below 1 ohm Connector B2 terminal 1 -Connector C terminal 1 10 kohm 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. (Scheme 48): With each connector still connected, measure the voltage between the body ground and these terminals (in this order): 1) terminal 1 of connector A, 2) terminal 1 of connector B, and 3) terminal 1 of connector C. EXAMPLE RESULTS: TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition Connector A terminal 1 - Body ground 5V Connector B terminal 1 - Body ground 5V Connector C terminal 1 - Body ground 0V If your results match the examples above, an open circuit exists in the wire harness between terminal 1 of connector B and terminal 1 of connector C.
3. CHECK FOR SHORT CIRCUITS If the wire harness is ground shorted (Scheme 49), 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. Standard (Scheme 50): TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition Connector A terminal 1 - Body ground Below 1 ohm Connector A terminal 2 - Body ground 10 kohm or higher HINT: Measure the resistance while lightly shaking the wire harness vertically and horizontally. If your results match the examples above, a short circuit exists between terminal 1 of connector A and terminal 1 of connector C. Disconnect connectors A and B, and measure the resistance. Standard (Scheme 51): TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition Connector A terminal 1 - Body ground 10 kohm or higher Connector B2 terminal 1 - 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: The connector should not be disconnected from the ECU. Perform the inspection from the backside of the connector on the wire harness side. 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 functioning one and check if the symptoms occur. If the trouble symptoms disappear, replace the ECU. Measure the resistance between the ECU ground terminal and body ground. Standard: 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 matter. Lastly, check the contact pressure of the female terminals.