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 

   NEXT 

2. CUSTOMER PROBLEM ANALYSIS 
   1. Ask the customer about the conditions and environment when the problem occurred.

   NEXT 

3. INSPECT BATTERY VOLTAGE 

   Standard voltage: 11 to 14 V 

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

   NEXT 

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 

      DTC RESULT
      
      

      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 the DTC check. 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 the symptom confirmation. 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.

   NEXT 

7. CIRCUIT INSPECTION OR PARTS INSPECTION 
   1. Identify the malfunctioning circuit or part.

   NEXT 

8. ADJUST, REPAIR OR REPLACE 
   1. Adjust, repair or replace the malfunctioning circuit or parts.

   NEXT 

9. CONFIRMATION TEST 
   1. After the adjustment, repairs or replacement, 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:

• In 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:
  PROBLEM ANALYSIS
  
  

  What	Vehicle model, system name
  When	Date, time, occurrence frequency
  Where	Road conditions
  Under what conditions?	Running conditions, driving conditions, weather conditions
  How did it happen?	Problem symptoms

HINT:

The diagnostic system in the LEXUS IS250/350 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 is more effective. Diagnostic functions are incorporated in the following system in the LEXUS IS250/350.

  REFERENCE CHART
  
  

  System	DTC Check (Normal Mode)	DTC Check (Check Mode)	Sensor Check/Test Mode (Input Signal Check)	Data List	Active Test
  SFI System (2GR-FSE)	◦	◦	-	◦	◦
  SFI System (4GR-FSE)	◦	◦	-	◦	◦
  Smart Access System with Push-button Start (for Starting)	◦	-	-	◦	◦
  Automatic Transmission System (A760E)	◦	◦	-	◦	◦
  Automatic Transmission System (A760H)	◦	◦	-	◦	◦
  Automatic Transmission System (A960E)	◦	◦	-	◦	◦
  For Wheel Drive Control System	◦	-	-	◦	◦
  Tire Pressure Warning System	◦	-	◦	◦
  Vehicle Stability Control System (w / VDIM)	◦	-	◦	◦	◦
  Vehicle Stability Control System (w / o VDIM)	◦	-	◦	◦	◦
  Power Tilt and Power Telescopic Steering Column System	◦	-	-	◦	◦
  Electric Steering Lock	◦	-	-	◦	◦
  Electronic Power Steering System	◦	-	-	◦	-
  Air Conditioning System	◦	-	-	◦	◦
  Pre-collision System	◦	-	-	◦	◦
  Airbag System	◦	◦	-	◦	-
  Occupant Classification System	◦	-	-	◦	-
  Seat Belt Warning System (w / Occupant Classification System)	-	-	-	-	◦
  Seat Belt Warning System (w /o Occupant Classification System)	-	-	-	-	◦
  Theft Deterrent System	-	-	-	◦	◦
  Engine Immobilizer System	◦	-	-	◦	◦
  Cruise Control System	◦	-	-	◦	◦
  Dynamic Radar Cruise Control System	◦	-	-	◦	◦
  Lighting System	◦	-	-	◦	◦
  Wiper and Washer System	-	-	-	◦	◦
  Power Door Lock Control System	◦	-	-	◦	◦
  Wireless Door Lock Control System	◦	-	-	◦	◦
  Smart Access System with Push-button Start (for Door Lock)	◦	-	-	◦	◦
  Meter / Gauge System	-	-	-	◦	◦
  Audio and Visual System	◦	-	-	-	-
  Navigation System	◦	-	-	-	-
  Intuitive Parking Assist System	◦	-	-	◦	◦
  Rear View Monitor System	-	-	-	-	-
  Power Window Control System	-	-	-	◦	◦
  Window Defogger System	-	-	-	-	◦
  Power Mirror Control System (w / Memory)	-	-	-	◦	◦
  Front Power Seat Control System (w / Seat Position Memory System)	-	-	-	◦	◦
  Luggage Compartment Door Opener System	-	-	-	◦	◦
  Sliding Roof System	-	-	-	◦	◦

• 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 

   NEXT 

2. MAKE A NOTE OF DTCS DISPLAYED AND THEN CLEAR MEMORY 

   NEXT 

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 

5. DTC CHECK 

   Result 

   DTC 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	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: SYSTEM NORMAL 

   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) 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. 

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 or not the malfunction occurs.

      NOTE: Applying strong vibration to relays may open 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.

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.
      Fig 1: Shaking Wire Harness Vertically And Horizontally

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002