Six-Step Troubleshooting Plan
Contents
1. about 1 2 inch on either HINT side e Ifthe damaged wire needs replacement make sure the same or larger diameter is used Also try to use the same wire color When removing the wire insulation be careful not to break or nick the wire strands e When splicing wires make sure the circuit is OFF 22 LEXUS Technical Training Wire Repair Manual The wire repair manual contains charts for terminal and connector ID and instructions for making repairs The terminals are listed by component that they are used with for easy reference Step 6 Check for Proper Operation Six Step Troubleshooting Plan TOYOTA After making the repair you must always verify that the problem was actually fixed Operate the circuit as thoroughly as you did when you first looked at the car making sure all of the functions and features of the circuit are working properly Sometimes a circuit has multiple problems which are causing it to be inoperative This re check of the circuit ensures that the customer will be satisfied A satisfied customer means that he or she will return to your dealership for service and tell their friends about their service experience too For the rest of this course you will be using a worksheet that incorporates all of the six steps that we have talked about Fill these worksheets in as you go through the diagnostic case studies that you ll do on the Simulator as a class or on the cars in the lab when2. split half method to isolate the problem or simply follow the System Circuit Schematic checking the items that are most accessible first you are still applying a process of elimination And that really is the heart of the diagnostic process There are specific techniques that you can use to isolate open circuits short to grounds parasitic loads and high resistance problems These techniques will be discussed in Section 5 of this handbook Body Electrical Diagnosis Course L652 19 Section 4 Circle the Possible Problem Areas Since the problem affects i alsa x ner a both bulbs you would concentrate on the area that is in parallel to both You could still have more than one problem which affect each bulb separately but the odds would be in your favor Most likely locations because it would affect both bulbs STOP LIGHT LH REAR COMB LIGHT LH 20 LEXUS Technical Training Where to Start Your Diagnosis Use the component location information in the EWD to determine where to make your inspections and which is the easiest to get to cote 7 See Page Wire Harness wit Spice Ports Code Sea Page Wr Harness wih Spica Pors O Loc amp tion of Splice Points Six Step Troubleshooting Plan L4 LIGHT FAILURE SENSOR STOP LIGHT LH REAR COMB LIGHT STOP LIGHT RH REAR COMB LIGHT RH Body Electrical Diagnosis Course L652 Section 4 Step 5 Correcting the trouble
3. they can quickly point to the areas you need to check and save you from making a lot of unnecessary inspections 10 LEXUS Technical Training Check for Possible Fuse or Ground Problem If the whole circuit is inoperative operate another circuit which uses the same fuse Then operate another circuit that uses the same ground point Six Step Troubleshooting Plan Look in the Power FROM POWER SOURCE SYSTEM SEE PAGE 5 Source Current Flow Section H for other circuits to operate 45a 10A STOP GAUGE 769 z 2 Switch Closed i s10 STOP LIGHT sw 30 c7 cto If NONE of the lights are working check for a fuse or ground point problem FIRST Use Section J Ground Point for other circuits to operate 3 REAR LIGHTS WARNING LIGHT Ty COMB METER Body Electrical Diagnosis Course L652 11 Section 4 If Any Part of the If any part of the circuit still works Circuit Works e You know that the power to the circuit and the main ground point are probably OK e You need to find out exactly which loads are working and which are not This will let you look for common wiring or connections between the bad parts of the circuit If any part of the problem circuit works it is extremely important to determine exactly which parts are working and which parts are not This step will save you from making unnecessary checks to parts of the circuit that are OK For example the customer c
4. you work in small groups Body Electrical Diagnosis Course L652 23 Section 4 24 LEXUS Technical Training
5. Section 4 Six Step Troubleshooting Plan VentytheGompiaint Baa a sake Symptoms Isolate the rouble eee esi freytie l a Check tor Proper Operation Introduce the six step troubleshooting process Learning Objectives Explain what needs to be done when verifying a problem Explain all the components of a related symptoms check ee mt Using the circuit tracing technique show how to analyze the symptoms and define the problem you need to diagnose a Show how to use the EWD when isolating a problem Explain repair techniques for wires terminals and connectors Perform a practice case study on the Lexus Body Electrical Simulator using the six step approach Body Electrical Diagnosis Course L652 1 Section 4 2 LEXUS Technical Training Six Step Troubleshooting Plan Introduction The Diagnostic Process Six Step Troubleshooting Plan You have now covered all of the tools used when diagnosing electrical problems e Basic electrical concepts e Use of the EWD e Tracing current flow through a system circuit diagram e Use of the DVOM amp jumper wires Now it s time to put all of these components together to diag
6. al inspection of the harness connectors and terminals with attention to the terminal spread Simulate the vibrations that are caused during driving by wiggling harnesses and connectors Keep in mind that as you move the harnesses or disconnect connectors you may cause the problem to temporarily fix itself While making your inspections try to minimize these changes to the circuit and keep track of which harnesses or connectors you have disconnected or moved Although it will be difficult in some cases be sure to identify exactly what is causing the problem and NEVER consider the vehicle s problem solved if it happens to magically fix itself 1 VIBRATION METHOD When vibration seems to be the major cause CONNECTORS Slightly shake the connector vertically and horizontally WIRE HARNESS Slightly shake the wire harness vertically and horizon tally The connector joint fulcrum of the vibration and body through portion are the major areas to be checked thoroughly Swing Slightly PARTS AND SENSORS Vibrate Slightty Apply slight vibration with a finger to the part of the sen N sor considered to be the problem cause and check if the ee 4 A malfunction occurs i Ph HINT Applying strong vibration to relays may result in open relays L6921404 Body Electrical Diagnosis Course L652 7 Section 4 Step 2 Determine the Related Symptoms How a Circuit is Related In general y
7. ation of the problem While operating the circuit you need to determine if the problem affects all of the circuit or just part of it Based upon how the circuit operates you can make some assumptions If the entire circuit system is dead this indicates that e There is a possible problem with a power fuse or ground circuit e The load or component is bad There are a large number of problems that could cause a component not to work from an open power wire or ground wire to a simple bad component Because of this you need a place to start your inspection To begin the easiest inspection to make would be to check the power and ground of the component by operating related circuits By using the EWD making a quick check of both power and ground is simple e Checking Power Look at the system circuit diagram and Section H Power Source Current Flow Chart to determine other circuits which share the fuse and check their operation Even if the fuse is not shared by another circuit simply locating and inspecting the fuse can be done quickly e Checking Ground Operating a shared circuit also provides a quick check of the ground circuit By using the Section J Ground Point information in the EWD you can find out if another circuit uses the same ground point If a circuit which shares the ground works OK you ll know that the ground point is OK Neither of these checks isolates the exact location of the circuit problem But
8. e done visually e If there is a known history of failures at a particular point e If multiple components circuits are inoperative Start with parts of the circuit that are common to both as opposed to looking for 2 separate problems The inspection process involves the use of all of the tools we discussed in Section 3 visual DVOM or jumper wire Make a mental plan of at least the first two initial checks you need to make If these initial checks do not find the cause of the problem they will at least lead you into making the additional checks to the circuit which will isolate the problem Remember that the location of the problem will be in one of the areas you circled on the wiring diagram If the accessibility of the circuit is good you can also apply the split half method Applying the split half method to the wiring diagram you would locate the middle of the bad part of the circuit After you find the connector nearest to that point you would determine which half B side or ground side of the circuit is bad by making an open circuit voltage or continuity check Once that is determined you would go to a connection in the middle of that bad section of the circuit and again determine which half of the circuit has a problem You continue to split the problem section of the circuit in half until the actual problem is isolated LEXUS Technical Training NOTE Six Step Troubleshooting Plan Whether you apply the
9. e the method for accessing the codes varies from system to system you ll need to turn to the specific RM section for each of these systems In these circuits the EWD is best used in conjunction with the RM and NCF It s location tables and color wiring diagrams provide a good supplement to the RM information Use the Repair Manual for Systems with Self Diagnostics l EF gt lt 8 La The RM is the first place to look when working with these systems The EWD is 1998 helpful especially with the Electri Ur gt E L color wiring diagrams and location information 1999 Repair Manual aen VOLUME 1 A Fig 4 8 L6221408 14 LEXUS Technical Training Six Step Troubleshooting Plan Diagnosing Ifthe circuit has an ECU with self diagnostic ability the general with DTCs diagnostic strategy is to 1 Always check for Diagnostic Trouble Codes DTC first and write them down Point any Freeze Frame data for reference 2 Clear the code memory and operate the system vehicle to see if the problem is intermittent or continuous 3 Ifthe trouble code s reappear follow the diagnostic tables in the RM 4 Ifthere are no codes but there is a problem present use the Problem Symptoms Table in the repair manual to direct you to the proper inspections 5 While diagnosing the circuit use the EWD to help you locate the components pins connectors or splices There are other techniques that you can use depend
10. h operating both the interior lighting and key warning buzzer circuits 8 LEXUS Technical Training Six Step Troubleshooting Plan How Circuits are Related Circuits are related through shared fuse power connections and through splices on the B or ground side of the component 15A 10A STOP GAUGE 2 Qp FROM POWER SOURCE SYSTEM SEE PAGE 56 z D J4 JUNCTION D CONNECTOR 4 T 3 D c7 cio 3 REAR LIGHTS WARNING LIGHT 7G COMB METER Parallel Circuit but sharing common path to Stop Fuse 15A Series Single Circuit to Hi Mount Lamp STOP LIGHT LH REAR COMB LIGHT LH Body Electrical Diagnosis Course L652 9 Section 4 How Much of the Circuit is Affected If Entire Circuit is Inoperative In order to know what loads or other circuits are related you ll need to look in the EWD System Circuit Diagram The wiring diagram will tell you what loads are connected in a particular circuit and how they are switched Section H Power Source Current Flow Chart as well as the power source system diagram will give you B side circuit information For ground point information Section J diagrams all of the splices on the ground side of the circuits By checking the operation of related circuits you will be eliminating parts of the circuit or components as the possible problem causes With fewer items that need to be checked you ll spend less time isolating the loc
11. ing on the system you are diagnosing This additional information on ECU system diagnosis is covered in L672 Diagnostic Trouble Codes DTCs DTC of the speed sensor check function Trouble Area Right front speed sensor DTCs are used mmany Low output voltage of right front speed sensor Sensor installation body electrical systems Right front speed sensor rotor including Cruise Control Left front speed sensor Anti lock Brakes Airbag Low output voltage of left front speed sensor Sensor installation and Engine Control Left front speed sensor rotor Syste ms Right rear speed sensor Low output voltage of right rear speed sensor Sensor installation Right rear speed sensor rotor Left rear speed sensor Low output voltage of teft rear speed sensor Sensor installation Left rear speed sensor rotor Abnormal ch i f right front H ipa rmal change in output voltage of right front speed sen Right front speed sensor rator norma change in output voltage of left front speed pai a Crane In OuIpUt Noreg pa Left front speed sensor rotor Abnormal change in output voltage of right rear speed sensor Abnormal change in output voltage of left rear speed sensor Left rear speed sensor rotor Right rear speed sensor rotor Fig 4 9 L6521409 Body Electrical Diagnosis Course L652 15 Section 4 16 Step 3 Analyze the Symptoms In order to fix the problem you need to know exactly what problem you
12. is probably the most straightforward step in the Correct the diagnostic process Making the repair to an electrical problem will Trouble always involve e Repair or replacement of a component e Wiring repair e Service to a circuit connection e Connectors e Terminals e Ground point Component When disconnecting and replacing components make sure that the Service Hints circuit is off or the battery is disconnected e Certain circuits require special handling The air bag system for example requires you to disconnect the battery and wait up to 90 seconds before servicing the system Always refer to the Repair Manual for special service precautions e Ifthe battery needs to be disconnected write down the customer s radio station pre sets Reprogram the stations and reset the clock after reconnecting the battery Wire Repair For any wiring connector or terminal repair your best resource is the Lexus Wire Harness Repair SST p n 00002 04201 02 This kit contains an assortment of replacement terminals wire tools and supplies that you will need to perform wire harness repairs Also the wire repair manual provided with the kit has charts for terminal and connector ID part numbers and complete instructions on how to make wire terminal and connector repairs e Cuts in the insulation should be wrapped with silicon tape supplied in the Wire Repair SST or covered with heat shrink tubing Be sure to overlap the repair by
13. ne the problem Trace the path of current flow in the circuit Power to L4 Pin 7 is verified by High Mount Light Both LH and RH Stop Light share Pin 7 with High Mount Light R6 STOP LIGHT LH REAR COMB LIGHT LH R8 STOP LIGHT RH REAR COMB LIGHT RH Fig 4 10 L65210 Body Electrical Diagnosis Course L652 17 Section 4 18 Step 4 Isolate the Problem Find the Possible Problem Areas Where to Begin The Split Half Method To isolate the problem there are three actions you need to make 1 On the wiring diagram find the areas that are possible problem areas 2 Determine where to begin making the checks 3 Make your inspections When analyzing the symptoms in step 4 you traced the paths of current flow in the parts of the circuit that were good You ll now see sections of the circuit that have NO tracing on it places where there is NO confirmed current flow Anywhere you have not traced current flow is a potential problem area If you are working with a photocopy of the diagram circle all of the locations where the problem could possibly be This gives you a good visual reference as to the places you ll potentially need to check Since any ONE of these locations you circled could be the cause of the problem you ll need to find a place to start In general the order you should inspect the potential problems is based upon e How easy it is to get to the component e Ifthe inspection can b
14. nose electrical problems It would be great if we could just walk up to a vehicle and instinctively know where an electrical problem was and what exactly had to be done to repair it This happens occasionally when fixing a problem that you have seen a number of times on a particular model Your experience from repeatedly fixing this problem allows you to make the repairs quickly with no wasted effort But what about problems that you see on only an occasional basis where there is no trend of past failures to help you To diagnose these types of problems in the least amount of time you need to make your diagnosis following a six step troubleshooting plan In L623 the Six Step Troubleshooting Plan was introduced These steps are 1 Verify the complaint 2 Determine the related symptoms 3 Analyze the symptoms 4 Isolate the trouble 5 Correct the trouble 6 Check for proper operation By using this troubleshooting plan you can minimize the amount of time spent diagnosing the circuit by performing only the checks that you need to make with an emphasis on checks that are the easiest to make Quickly finding and fixing an electrical problem doesn t depend on luck but on your skills applying what you know about circuits using the EWD and devising a strategy to isolate the location of the problem The six step approach is a way to organize your efforts keeping you on track while you are troubleshooting the problem B
15. noticing a characteristic of the vehicle There are no fixes for these non problems The best way to identify this type of condition is to compare the customer s vehicle to a known good vehicle 1999 Lexus Owner s Manual ES 300 ELECTRICAL COMPONENTS ELECTRICAL COMPONENTS REPLACING LIGHT BULBS 6 LEXUS Technical Training Intermittent or Continuous Intermittent Problem Simulation Try to simulate the conditions under which the problem occurred The ES 300 Repair Manual has a Troubleshooting Section which was introduced to assist in diagnosing problems with ECU controlled systems Six Step Troubleshooting Plan When verifying the problem you must also determine if the problem is continuous or intermittent If the problem is continuous or not inter mittent it should be fairly obvious when you operate the suspect system Intermittent problems can be more difficult to find If the problem is intermittent you ll need to know as much information as possible from the ASM or customer directly about the conditions that were present when the problem occurred for the customer For example electrical problems can be triggered by ambient temperature vibrations from road conditions weather or the type of driving only on turns hills etc How the customer actually operates the system can also be a factor If the conditions are repeated and the problem does not re occur make a thorough visu
16. ody Electrical Diagnosis Course L652 3 Section 4 Six Step Troubleshooting Plan Vary ins Gompiaint V Datsuns tis rliakitsel Syinoteout y ANE 43 US SUAS fs9kite tyairougl y Go orrecithe i roupie CHECKT OTIPTOPET Operation 4 LEXUS Technical Training Step 1 Verify the Complaint Identify the Problem Six Step Troubleshooting Plan This is the first step in any diagnostic process When you are handed a repair order with a customer s complaint on it there are three things that you must do 1 You must be able to identify the problem the customer noted 2 You must determine if it is a problem or not 3 Ifthere is a problem determine if it is intermittent or continuous The average customer is not a technically oriented person When they describe a problem it s not always going to be easy to understand them especially if you weren t the person who wrote it on the RO Your knowledge about how each system works is very important in recognizing what the customer is talking about If you don t know how a system is supposed to operate when it s OK you won t know when it is broken Because of the number of systems circuits on the vehicle and the increased use of ECU type controls in them it is becoming more difficult to keep up with the details on how all the systems model to model operate The best places to look for information on how a system should operate are the System O
17. omplaint is that the stop lights do not work As you step on the brake you notice that the high mount stop light works Knowing this verifies that a large portion of the circuit is OK By eliminating parts of the circuit that are OK the number of places you need to check is reduced This is what checking the related symptoms is all about 12 LEXUS Technical Training Eliminate Parts of the Circuit If one or more of the stop lights work you know that the fuse the grounds and part of the wiring are OK Verified OK a 15A STOP 709 2 Switch Closed i 10 i STOP LIGHT sw Six Step Troubleshooting Plan FROM POWER SOURCE SYSTEM SEE PAGE 56 140A GAUGE D us p JUNCTION i CONNECTOR Rear Lights Warning Light Illuminates D ci0o oer ANING LIGHT A 7 8 High Mount Light Works E H gt B 1 11 J337 A JUNCTION TERT CONNECTOR i erifi 5 RY Body Electrical Diagnosis Course L652 Both Stop Lights Do Not Work 13 Section 4 Circuits with When working on a system that has self diagnostic capability the Self Diagnostics New Car Features NCF book and the Repair Manual RM are the only places to find information about how to access the Diagnostic Trouble Codes and what each individual code means The RM also contains specific diagnostic procedures for each circuit including a table to direct you in diagnosing problems that do not set trouble codes Becaus
18. ou cannot make an accurate diagnosis or repair of a problem you cannot duplicate If the situation warrants it call Technical Assistance to see if there have been any other reported cases of the problem or for advice on how to proceed with the vehicle Now that you have verified that there is a problem you need to examine the problem symptoms more thoroughly The related symptoms check is basically an operational check so you won t need any tools except for the EWD The major goal of this check is to determine 1 How much of the circuit is affected 2 Find clues to the location of the problem by operating other circuits related or connected to the problem area To say determine the related symptoms sounds complex but this is one of the most important and time saving steps you can make in the diagnostic process In this step you need to operate the problem circuit thoroughly noting exactly what is and what is not working Based upon your observations make checks to the related circuits Circuits are related to another circuit because of a parallel connection e Most electrical circuits consist of two or more loads that are connected in parallel e Entirely different circuits are related to another circuit by a parallel connection to common power sources fuses or ground points e Shared sensor or switch functions in which a single switch operates a number of different circuits such as the LH front door courtesy switc
19. re dealing with When verifying the problem you were able to get a better understanding of the customer s complaint After making the related symptoms checks you may have found other circuits that are or are not affected At this point you need to stop and put all of this information together to specifically define e Exactly which components circuits are affected both the customer s complaint and any related symptoms e What kind of problem you need to look for open short to ground high resistance feedback e When it occurs what operating conditions key ON driver s door open etc After doing this go to the System Circuit Diagram or a photocopy of the diagram if possible and trace the current flow paths in the parts of the circuit that are confirmed as working By tracing the current flow paths you will have a visual reference of areas of the circuit you dont need to check Areas that you have NOT traced are all places that a possible problem could exist All of this up front work will have a payoff Less time spent making checks on the car LEXUS Technical Training Six Step Troubleshooting Plan Trace the Paths of Current Flow The sh Problem Definition e sh aded areas indicate FROM POWER SOURCE SYSTEM SEE PAGE 56 Left and Right Stop Lights do not where the circuit is OK 5 Tracing current flow here is work High Mount Stop Light OK the same as you did earlier in the course Clearly defi
20. utline in the EWD and the Owner s Manual Verify the Complaint Very the Co Sample Customer Complaint Stop Lights Do Not Identify what the Customer is describing ompla Is it a problem Is it intermittent or continuous Step on the brake pedal look at the stop lights Work The problem happens every time the brake pedal is depressed Body Electrical Diagnosis Course L652 5 Section 4 Does a Problem Exist Use the Owner s Manual as a Reference Like the EWD system outline the Owner s Manual is a good resource for information on how different systems or circuits are supposed to operate Sometimes what seems like a problem to a customer is actually a normal function of the circuit For example the customer complaint could be about the power door locks When the key is in the ignition with the door open the power door locks won t lock A condition such as this is not a problem but a normal function of the Power Door Lock ECU and its key confine feature which is designed to prevent the customer from locking their keys in the car For the customer information about the operation on all the electrical systems on the vehicle can be found in the Owner s Manual For you detailed information about the operation of different electrical systems can be found in the EWD as well as in the Repair Manual Body Electrical section There are also instances where the customer is
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