How To Proceed With Troubleshooting

HINT.

Perform troubleshooting in accordance with the procedures below The following is an outline of basic troubleshooting procedures. Confirm the troubleshooting procedures for the circuit you are working on before beginning troubleshooting

1. VEHICLE BROUGHT TO WORKSHOP 
2. CUSTOMER PROBLEM ANALYSIS 
   1. Ask the customer about the conditions and environment when the problem occurred
3. INSPECT BATTERY VOLTAGE 

   Standard voltage: 11 to 14 V 

   If the voltage is below 11V, recharge or replace the battery before proceeding. 

4. SYMPTOM CONFIRMATION AND DTC (AND FREEZE FRAME DATA) CHECK 
   1. Visually check the wire harnesses, connectors and fuses for open and short circuits.
   2. Warm up the engine to the normal operating temperature
   3. Confirm the problem symptoms and conditions, and check for DTCs

      Result 

      PROBLEM ANALYSIS POINTS
      
      

      Result	Proceed to
      DTC is output	A
      DTC is not output	B

   B: GO TO STEP   6

   A: Go to next step 

5. DTC CHART 
   1. Check the results obtained in step  4. Then find the output DTC in the DTC chart Look at the "Trouble Area" column for a list of potentially malfunctioning circuits and/or parts.

   NEXT: GO TO STEP   7

6. PROBLEM SYMPTOMS CHART 
   1. Check the results obtained in step  4. Then find the problem symptoms in the problem symptoms table Look at the "Suspected Area" column for a list of potentially malfunctioning circuits and/or parts
7. CIRCUIT INSPECTION OR PARTS INSPECTION 
   1. Identify the malfunctioning circuit or part
8. ADJUST, REPAIR OR REPLACE 
   1. Adjust, repair or replace the malfunctioning circuit or part
9. CONFIRMATION TEST 
   1. After the adjustment, repairs or replacement of components, 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 the malfunction occurred the first time

   NEXT: END 

HINT.

• When troubleshooting, confirm that the problem symptoms have been accurately identified Preconceptions should be discarded in order to make an accurate judgment To clearly understand what the problem symptoms are, it is extremely important to ask the customer about the problem and the conditions at the time the malfunction occurred
• Gather as much information as possible for reference Past problems that seem unrelated may also help in some cases
• The following 5 items are important points in the problem analysis.

HINT.

The diagnostic system in this vehicle has various functions

• 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.
• 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 can be more effective Diagnostic functions are incorporated in the following system in this vehicle

• In the DTC check, it is very important to determine whether the problem indicated by the DTC either. 1) still occurs, or 2) occurred in the past but has 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 related to the problem Follow the procedures listed in the flowchart in the correct order
• The following flowchart shows how to proceed with troubleshooting using the DTC check. Directions from the flowchart will indicate how to proceed either to DTC troubleshooting or to the troubleshooting of each problem symptom

1. DTC CHECK 
2. MAKE A NOTE OF DTC DISPLAYED AND THEN CLEAR MEMORY 
3. SYMPTOM CONFIRMATION 

   Result 

   RESULT REFERENCE
   
   

   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 
5. DTC CHECK 

   Result 

   RESULT REFERENCE
   
   

   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 

   ITEMS DESCRIPTION
   
   

   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. 

   B: END 

   A: TROUBLESHOOTING OF EACH PROBLEM SYMPTOM 

   The problem still occurs in a place other than the diagnostic circuit (the DTC displayed first is either for a past problem or a secondary problem)

HINT

The most difficult case in troubleshooting is when no problem symptoms occur In such a case, a thorough 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 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) are difficult to reproduce. The symptom simulation tests below are effective substitutes for the conditions and can be applied to 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. 

1. VIBRATION METHOD When a malfunction seems to occur as a result of vibration.
   1. PART AND SENSOR

      Apply slight vibration with a finger to the part of the sensor suspected to be the cause of the problem, and check whether the malfunction occurs

      NOTE: Applying strong vibration to relays may open the relays.
   2. CONNECTORS

      Slightly shake the connector vertically and horizontally.

   3. WIRE HARNESS

      Slightly shake the wire harness vertically and horizontally.

      HINT

      The connector joint and fulcrum of the vibration are the major areas that should be checked thoroughly

   Fig 1: Checking Connectors And Wire Harness
   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. HEAT METHOD When a malfunction seems to occur when the area in question is heated
   1. 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 60C (140°F). Exceeding this temperature may damage the components.
      • Do not apply heat directly to the parts in the ECU.
3. WATER SPRINKLING METHOD When a malfunction seems to occur on a rainy day or in high-humidity
   1. Sprinkle water onto the vehicle and check if the malfunction occurs
      NOTE:

      • Never sprinkle water directly into the engine compartment. Indirectly change the temperature and humidity by spraying water onto the front of the radiator.
      • Never apply water directly onto the electronic components.
        Fig 2: Precaution For Water Sprinkling Method

        Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      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

4. HIGH ELECTRICAL LOAD METHOD: When a malfunction seems to occur when an electrical load is excessive
   1. Turn on the heater blower, headlights, rear window defogger and all other electrical loads. Check if the malfunction reoccurs
   Fig 3: Identifying High Electrical Load Method

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Look for output Diagnostic Trouble Codes (DTCs) (from the DTC checks) in the appropriate article's Diagnostic Trouble Code Chart. Use the chart to determine the trouble area and the proper inspection procedure A description of each of the chart's columns is shown in the table below

When no DTC is output but the problem still occurs, use the Problem Symptoms Table The suspected areas (circuits or parts) for each problem symptoms are shown in the table The suspected areas are listed in order of probability A description of each of the chart columns is shown in the following table

HINT:

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

A description of the main areas of each circuit inspection is shown in the following table.