Introduction: Diagnosis Scion xA I

FOR USING OBDII 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. 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. If 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

Note. Carry out troubleshooting in accordance with the procedures below. Only a basic procedure is shown. Details in the Diagnostics Section show the most effective methods for each circuit. Confirm the troubleshooting procedures for the relevant circuit before beginning troubleshooting.

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: 11 - 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 related 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 part using the DTC chart. Go to step 6
5. PROBLEM SYMPTOMS CHART Check the results obtained in step 3 . Confirm the inspection procedures for the system or part using the problem symptoms table.
6. CIRCUIT INSPECTION OR PARTS INSPECTION Confirm the circuit in the system or the part that should be checked using the problem symptoms table or the results obtained in step 4 .
7. REPAIR Repair the affected system or part according to the instructions in step 6 .
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

Note. The diagnostic system in the SCION xA fulfills various functions.

1. The first function is the Diagnostic Trouble Code (DTC) Check. In a DTC Check, a previous malfunction's DTC can be checked by a technician during troubleshooting. (A DTC is a code stored in the ECU memory whenever a malfunction in the signal circuits to the ECU occurs.)
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 check functions, the problem areas can be narrowed down and troubleshooting is more effective. Diagnostic functions are incorporated in the following systems in the SCION xA: DIAGNOSTIC FUNCTIONS CHART System Diagnostic Trouble Code Check Diagnostic Test Mode (Active Test) SFI System ? (with Check Mode) ? ABS with EBD System ? ? Electronically Controlled Automatic Transmission [ECT] ? (with Check Mode) ? Supplemental Restraint System ?
3. In the DTC Check, it is very important to determine whether the problem indicated by the DTC is: 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 conditions, as shown in the table below. Never skip the DTC Check. Failure 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. Follow the procedures listed above in the correct order.
4. A flow chart showing how to proceed with troubleshooting using the DTC Check is shown below. Directions from the flow chart will indicate how to proceed either to DTC troubleshooting or to the troubleshooting of the problem symptoms table.

1. DTC CHECK
2. MAKE A NOTE OF DTCS DISPLAYED AND THEN CLEAR THE MEMORY
3. SYMPTOM CONFIRMATION SYMPTOM CONFIRMATION ? Symptoms Exist ? No Symptoms Exist a : Go to step 5 b : Go to next step.
4. SIMULATION TEST USING THE SYMPTOM SIMULATION METHODS
5. DTC CHECK DTC DISPLAYING ? DTC Displayed ? No DTC a : Troubleshooting of problem indicated by DTC b : Go to next step.
6. SYMPTOM CONFIRMATION SYMPTOM CONFIRMATION ? No Symptoms Exist ? Symptoms Exist If a DTC was displayed in the initial DTC Check, it indicates that the 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-204091-S27495652472005110800000) ). 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 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 lead to mistakes or delays.

For example

With a problem that only occurs when the engine is cold or occurs as result of vibration caused by the road during driving, the problem can never be determined as long as the symptom 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 effected 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 32

Scheme 33

Scheme 34

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. NOTE: Applying strong vibration to relays may open a relay. 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 whether not 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 a high-humidity. Sprinkle water onto the vehicle and check whether or not the malfunction occurs. 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. NOTE: If the vehicle has or had a water leakage problem, the leakage may have damaged the ECU or connections. Lock for evidence of corrosion or shorts. Proceed with caution during water tests.
4. OTHERS: When a 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

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) diagnostic trouble code chart is shown below as an example.

Scheme 35

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.

Note. 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 36

CIRCUIT INSPECTION

How to read and use each page is shown below.

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Scheme 51

1. BASIC INSPECTION RESISTANCE MEASURING CONDITION OF ELECTRONIC PARTS Unless stated, all resistance is measured at an ambient temperature of 20°C (68°F). 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 when the engine has cooled down. HANDLING OF CONNECTOR 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. CONNECTOR CHECKING POINTS 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, or 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 platting 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 a vinyl tape.
2. CHECK OPEN CIRCUIT For an open circuit in the wire harness in (Scheme 43), 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: 1 ohms or less NOTE: Measure the resistance while lightly shaking the wire harness vertically and horizontally. (Scheme 44): Between terminal 1 of connector A and terminal 1 of connector C --> 10 kohms or higher Between terminal 2 of connector A and terminal 2 of connector C --> Below 1 ohms In this case, 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. (Scheme 45): Between terminal 1 of connector A and terminal 1 of connector B1 --> Below 1 ohms Between terminal 1 of connector "B2" and terminal 1 of connector "C" --> 10 kohms or higher In this case, 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 46): 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 47), 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 kohms or higher NOTE: Measure the resistance while lightly shaking the wire harness vertically and horizontally. In the case of (Scheme 48): Between terminal 1 of connector A and body ground --> Below 1 ohms Between terminal 2 of connector A and body ground --> 10 kohms or higher In this case, 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. (Scheme 49): Between terminal 1 of connector "A" and body ground --> 10 kohms or higher Between terminal 1 of connector "B2" and body ground --> Below 1 ohms In this case, 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. 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 evidence of bending, corrosion or foreign material. Lastly check the contact pressure of the female terminals.