How To Proceed With Troubleshooting

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Carry out troubleshooting in accordance with the procedure on the following page. Here, only the basic procedure is shown. Details are provided in Diagnostics section, showing the most effective methods for each circuit. Confirm the troubleshooting procedures first for the relevant circuit before beginning troubleshooting of that circuit.

Vehicle Brought to Workshop

Customer Problem Analysis

Ask the customer about the conditions and the environment when the problem occurred.

'Symptom Confirmation and Diagnostic Trouble Code Check

'Symptom Confirmation and Diagnostic Trouble Code Check

Symptom Simulation

Symptom Simulation

Diagnostic Trouble Code Chart

Confirm the symptoms and the problem conditions, and check the diagnostic trouble codes. (When the problem symptoms do not appear during confirmation, use the symptom simulation method described later on.)

Problem Symptoms Table

Circuit Inspection or Parts Inspection /

Repair

Confirmation Test

Check the results obtained in Step 2, then confirm the inspection procedure for the system or the part which should be checked using the diagnostic trouble code chart or the problem symptoms table.

Check and repair the affected system or part in accordance with the instructions in Step 6.

After completing repairs, confirm that the problem has been eliminated.

(If the problem is not reproduced, perform the confirmation test under the same conditions and in the same environment as when it occurred for the first time.)

1. CUSTOMER PROBLEM ANALYSIS

In troubleshooting, the problem symptoms must be confirmed accurately and all preconceptions must be cleared away in order to give an accurate judgment. To ascertain just what the problem symptoms are, it is extremely important to ask the customer about the problem and the conditions at the time it occurred. Important Point in the Problem Analysis:

The following 5 items are important points in the problem analysis. Past problems which are thought to be unrelated and the repair history, etc. may also help in some cases, so as much information as possible should be gathered and its relationship with the problem symptoms should be correctly ascertained for reference in troubleshooting. A customer problem analysis table is provided in Diagnostics section for each system for your use.

-Important Points in the Customer 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

(Sample) Engine control system check sheet.

CUSTOMER PROBLEM ANALYSIS CHECK

ENGINE CONTROL SYSTEM Check Sheet

Inspector's Name

ENGINE CONTROL SYSTEM Check Sheet

Inspector's Name

Customer's Name

Model and Model Year

Driver's Name

Frame No.

Data Vehicle Brought in

Engine Model

License No.

Odometer Reading

km miles

Engine does not Start

□ Engine does not crank □ No initial combustion □ No complete combustion

□ Difficult to Start

□ Engine cranks slowly

□ Other

□ Poor Idling

□ Incorrect first idle □ Idling rpm is abnormal □ High ( rpm) □ Low ( rpm)

□ Rough idling □ Other

Drive ability

□ Hesitation □ Back fire □ Muffler explosion (after-fire) □ Surging

□ Knocking □ Other

Engine Stall

□ Soon after starting □ After accelerator pedal depressed

□ After accelerator pedal released □ During A/C operation

□ Shifting from N to D □ Other

Others

Qstant □ Sometimes ( times per day/month)

Qstant □ Sometimes ( times per day/month)

2. SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK

The diagnostic system in the PRIUS fulfills various functions. The first function is the Diagnostic Trouble Code Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory at the time of occurrence, to be output by the 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 check functions, the problem areas can be narrowed down quickly and troubleshooting can be performed effectively. Diagnostic functions are incorporated in the following systems in the PRIUS.

System

Diagnostic Trouble Code Check

Input Signal Check (Sensor Check)

Diagnostic Test Mode (Active Test)

Engine

O (with Check Mode)

O

O

Hybrid Vehicle Control System

O

O

O

HV Battery Control System

O (with Check Mode)

O

O

Anti-Lock Brake System With EBD & RBS

O

O

O

Electric Motor Power Steering

O

Supplemental Restraint System

O

Cruise Control System

O

O

Multiplex Communication System

O

Navigation System

O

Air Conditioning System

O

O

In diagnostic trouble code check, it is very important to determine whether the problem indicated by the diagnostic trouble code is still occurring or occurred in the past but returned to normal at present. In addition, it must be checked in the problem symptom check whether the malfunction indicated by the diagnostic trouble code is directly related to the problem symptom or not. For this reason, the diagnostic trouble codes should be checked before and after the symptom confirmation to determine the current conditions, as shown in the table below. If this is not done, it may, depending on the case, result in unnecessary troubleshooting for normally operating systems, thus making it more difficult to locate the problem, or in repairs not pertinent to the problem. Therefore, always follow the procedure in correct order and perform the diagnostic trouble code check.

DIAGNOSTIC TROUBLE CODE CHECK PROCEDURE

Diagnostic Trouble Code Check (Make a note of and then clear)

Confirmation of Symptoms

Diagnostic Trouble Code Check

Problem Condition

Diagnostic Trouble Code Display

Problem symptoms exist >

Same diagnostic trouble code is displayed

Problem is still occurring in the diagnostic circuit

Normal code is displayed

The problem is still occurring in a place other than in the diagnostic circuit (The diagnostic trouble code displayed first is either for a past problem or it is a secondary problem)

No problem symptoms exist

The problem occurred in the diagnostic circuit in the past

Normal Code Display^

Problem symptoms exist

Normal code is displayed

The problem is still occurring in a place other than in the diagnostic circuit

No problem symptoms exist

Normal code is displayed

The problem occurred in a place other than in the diagnostic circuit in the past

Taking into account the points on the previous page, a flow chart showing how to proceed with troubleshooting using the diagnostic trouble code check is shown below. This flow chart shows how to utilize the diagnostic trouble code check effectively, then by carefully checking the results, indicates how to proceed either to diagnostic trouble code troubleshooting or to troubleshooting of problem symptoms table.

Diagnostic trouble code check

Making a note of and clearing of the diagnostic trouble codes displayed

Symptom confirmation

Problem symptoms exist

No problem symptoms exist

Simulation test using the symptom simulation methods

Diagnostic trouble code check

3. SYMPTOM SIMULATION

The most difficult case in troubleshooting is when there are no problem symptoms occurring. In such cases, a thorough customer problem analysis must be carried out, then simulate the same or similar conditions and environment in which the problem occurred in the customer's vehicle. No matter how much experience a technician has, or how skilled he may be, if he proceeds to troubleshoot without confirming the problem symptoms he will tend to overlook something important in the repair operation and make a wrong guess somewhere, which will only lead to a standstill. For example, for a problem which only occurs when the engine is cold, or for a problem which occurs due to vibration caused by the road during driving, etc., the problem can never be determined so long as the symptoms are confirmed with the engine hot condition or the vehicle at a standstill. Since vibration, heat or water penetration (moisture) is likely cause for problem which is difficult to reproduce, the symptom simulation tests introduced here are effective measures in that the external causes are applied to the vehicle in a stopped condition. Important Points in the Symptom Simulation Test:

In the symptom simulation test, the problem symptoms should of course be confirmed, but the problem area or parts must also be found out. To do this, narrow down the possible problem circuits according to the symptoms before starting this test and connect a tester beforehand. After that, carry out the symptom simulation test, judging whether the circuit being tested is defective or normal and also confirming the problem symptoms at the same time. Refer to the problem symptoms table for each system to narrow down the possible causes of the symptom.

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 horizontally. The connector joint, fulcrum of the vibration, and body through portion are the major areas to be checked thoroughly.

Swing Slightly

FI2331 FI2332

PARTS AND SENSOR

Vibrate Slightly

Apply slight vibration with a finger to the part of the sensor considered to be the problem cause and check that the malfunction occurs.

Vibrate Slightly

P0110 Sensor Yaris

HINT:

Applying strong vibration to relays may result in open relays.

FI2330

V07268

2

HEAT METHOD: When the problem seems to occur when the suspect area is heated.

Heat the component that is the likely cause of the malfunction with a hair dryer or similar object. Check to see if the malfunction occurs.

NOTICE:

(1) Do not heat to more than 60 °C (140 °F). (Temperature is limited not to damage the components.)

(2) Do not apply heat directly to parts in the ECU.

/lMalfunc-\

FI2334

3

WATER SPRINKLING METHOD: When the malfunction seems to occur on a rainy day or in a high-humidity condition.

Sprinkle water onto the vehicle and check to see if the malfunction occurs. NOTICE:

(1) Never sprinkle water directly into the engine compartment, but indirectly change the temperature and humidity by applying water spray onto the radiator front surface.

(2) Never apply water directly onto the electronic components.

HINT:

If a vehicle is subject to water leakage, the leaked water may contaminate the ECU. When testing a vehicle with a water leakage problem, special caution must be taken.

Fl 6649

4

OTHER: When a malfunction seems to occur when electrical load is excessive.

Turn on all electrical loads including the heater blower, head lights, rear window defogger, etc. and check to see if the malfunction occurs.

4. DIAGNOSTIC TROUBLE CODE CHART

The inspection procedure is shown in the table below. This table permits efficient and accurate troubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check. Proceed with troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponding to the diagnostic trouble codes displayed. The engine diagnostic trouble code chart is shown below as an example.

Indicates the diagnostic trouble code.

• Page or Instructions

Indicates the page where the inspection procedure for each circuit is to be found, or gives instructions for checking and repairs.

• Trouble Area Indicates the suspect area of the problem.

• Detection Item Indicates the system of the problem or contents of the problem.

CHART (SAE Controlled) <

Parameters listed in the chart may not pe exactly the same as your reading due to the type of instrument or other factors.

If a malfunction code is displayed during the DTC check mode, check the circuit for that code listed in the table below. For details of each code, turn /o the page referred to under the "See page" for the respective "DTC No." in the DTC chart.

DTC No. (See page)

Detection Item 1

Trouble Area J

MIL*

Memory

P0100 (DI-24)

Mass Air Flow Circuit Malfunction

• Open or short in mass air flow meter circuit

• ECM

O

o

P0101 (DI-28)

Mass Air Flow Circuit Range/ Performance Problem

• Mass air flow meter

o

o

P0110 (DI-29)

Intake Air Temp. Circuit Malfunction

• Open or short in intake air temp. sensor circuit

• Intake air temp. sensor

• ECM

o

o

P0115 (DI-33)

Engine Coolant Temp. Circuit Malfunction

• Open or short in engine coolant temp. sensor circuit

• Engine coolant temp. sensor

• ECM

o

o

P0116 (DI-37)

Engine Coolant Temp.

Circuit Range/ Performance Problem

• Engine coolant temp. sensor

• Cooling system

• Open or short in throttle position sensor circuit

o

o

Position Sensor/Switch nction u Throttle position sensor u ECM

Position Sensor/Switch nction u Throttle position sensor u ECM

osition Sensor/ Switch ormance Prob-

u Throttle position sensor

5. PROBLEM SYMPTOMS TABLE

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

When the problem is not detected by the diagnostic system even though the problem symptom is present, it is considered that the problem is occurring outside the detection range of the diagnostic system, or that the problem is occurring in a system other than the diagnostic system.

1985 4runner Circuit Open Relay

6. CIRCUIT INSPECTION

How to read and use each page is shown below.

Diagnostic Trouble Code No. and Detection Item

P0325

Circuit Description The major role and operation, etc. of the circuit and its component parts are explained.

Knock Sensor 1 Circuit Malfunction

CIRCUIT DESCRIPTION

Knock sensor is fitted to the cylinder block to detect engine knocking. This sensor contains a piezoelectric element which generates a voltage when it becomes deformed, which occurs when the cylinder block vibrates due to knocking. If engine knocking occurs, ignition timing is retarded to suppress it.

CIRCUIT DESCRIPTION

Knock sensor is fitted to the cylinder block to detect engine knocking. This sensor contains a piezoelectric element which generates a voltage when it becomes deformed, which occurs when the cylinder block vibrates due to knocking. If engine knocking occurs, ignition timing is retarded to suppress it.

DTC No.

DTC Detecting Condition

Trou

ble Area

P0325

No knock sensor 1 signal to ECM with ehgine speed 1,200 rpm or more. n.

• ECM

Ck sensorl circuit ieness)

If the ECM detects the above diagnosis conditions, it operates the failsafe function in which the corrective retard angle value is set to the maximum value.

If the ECM detects the above diagnosis conditions, it operates the failsafe function in which the corrective retard angle value is set to the maximum value.

Indicates the diagnostic trouble code, diagnostic trouble code set parameter and suspect area of the problem.

WIRING DIAGRAM

Knock Sensor 1

Wiring Diagram

This shows a wiring diagram of the circuit. Use this diagram together with ELECTRICAL WIRING DIAGRAM to thoroughly understand the circuit.

Wire colors are indicated by an alphabetical code.

The first letter indicates the basic wire color and the second letter indicates the color of the stripe.

V08423

• Indicates the position of the ignition switch during the check.

LOCK

(^T) Ignition Switch LOCK (OFF)

START

Ignition Switch START

Ignition Switch ON Çf) Ignition Switch ACC

Use the inspection procedure to determine if the circuit is normal or abnormal, and, if it is abnormal, use it to determine whether the problem is located in the sensors, actuators, wire harness or ECU.

1 Check continuity between terminal KNK of ECM connector and body ground.

PREPARATION:

(a) Remove the glove compartment (See page SF-68).

(b) Disconnect the E6 connector of ECM.

CHECK:

Measure resistance between terminal KNK of ECM connector

1 Check continuity between terminal KNK of ECM connector and body ground.

PREPARATION:

(a) Remove the glove compartment (See page SF-68).

(b) Disconnect the E6 connector of ECM.

CHECK:

Measure resistance between terminal KNK of ECM connector

• Indicates the place to check the voltage or resistance.

• Indicates the connector position to checked, from the front or back side. nrnrv

Wire Harness

Wire Harness

Check from the connector back side. (with harness)

Check from the connector front side. (without harness) In this case, care must be taken not to bend the terminals

Indicates the condition of the connector of ECU during the check. KNK

Indicates the condition of the connector of ECU during the check. KNK

E6 Connector

Connector being checked is connected.

r\ ffiffl T

T\ E6 Connector Connector being checked is disconnected

V08425

FI0048

HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE

1. CONNECTOR CONNECTION AND TERMINAL INSPECTION

• For troubleshooting, diagnostic trouble code charts or problem symptom table are provided for each circuit with detailed inspection procedures on the following pages.

• When all the component parts, wire harnesses and connectors of each circuit except the ECU are found to be normal in troubleshooting, then it is determined that the problem is in the ECU. Accordingly, if diagnosis is performed without the problem symptoms occurring, refer to Step 8 to replace the ECU. So always confirm that the problem symptoms are occurring, or proceed with inspection while using the symptom simulation method.

• The instructions "Check wire harness and connector" and "Check and replace ECU" which appear in the inspection procedure, are common and applicable to all diagnostic trouble codes. Follow the procedure outlined below whenever these instructions appear.

OPEN CIRCUIT:

This could be due to a disconnected wire harness, faulty contact in the connector, and a connector terminal pulled out, etc. HINT:

• It is rarely the case that a wire is broken in the middle of it. Most cases occur at the connector. In particular, carefully check the connectors of sensors and actuators

• Faulty contact could be due to rusting of the connector terminals, to foreign materials entering terminals or a deformation of connector terminals. Simply disconnecting and reconnecting the connectors once changes the condition of the connection and may result in a return to normal operation. Therefore, in troubleshooting, if no abnormality is found in the wire harness and connector check, but the problem disappears after the check, then the cause is considered to be in the wire harness or connectors.

SHORT CIRCUIT:

This could be due to a contact between wire harness and the body ground or to a short circuit occurred inside the switch, etc. HINT:

When there is a short circuit between the wire harness and body ground, check thoroughly whether the wire harness is caught in the body or is clamped properly.

2. CONNECTOR HANDLING

When inserting tester probes into a connector, insert them from the rear of the connector. When necessary, use mini test leads. For water resistant connectors which cannot be accessed from behind, take good care not to deform the connector terminals.

Terminals Ecm Toyota Tacoma 1996

3. CONTINUITY CHECK (OPEN CIRCUIT CHECK)

(a) Disconnect the connectors at both ECU and sensor sides.

(b) Measure the resistance between the applicable terminals of the connectors. Resistance: 1 Q or less

HINT:

Measure the resistance while lightly shaking the wire harness vertically and horizontally.

Twin Coil Antenna

4. RESISTANCE CHECK (SHORT CIRCUIT CHECK)

(a) Disconnect the connectors on both ends.

(b) Measure the resistance between the applicable terminals of the connectors and body ground. Be sure to carry out this check on the connectors on both ends. Resistance: 1 MQ or higher

HINT:

Measure the resistance while lightly shaking the wire harness vertically and horizontally.

5. VISUAL CHECK AND CONTACT PRESSURE CHECK

(a) Disconnect the connectors at both ends.

(b) Check for rust or foreign material, etc. in the terminals of the connectors.

(c) Check crimped portions for looseness or damage and check that the terminals are secured in lock portion.

HINT:

The terminals should not come out when pulled lightly from the back.

(d) Prepare a test male terminal and insert it in the female terminal, then pull it out. NOTICE:

When testing a gold-plated female terminal, always use a gold-plated male terminal.

HINT:

When the test terminal is pulled out more easily than others, there may be poor contact in that section.

Matteoppgaver

6. CHECK OPEN CIRCUIT

For the open circuit in the wire harness in Fig. 1, perform "(a) Continuity Check" or "(b) Voltage Check" to locate the section.

(a) Check the continuity.

(1) Disconnect connectors "A" and "C" and measure the resistance between them.

Between terminal 1 of connector "A" and terminal 1 of connector "C" ^ No continuity (open) Between terminal 2 of connector "A" and terminal 2 of connector "C" ^ Continuity Therefore, it is found out that there is an open circuit between terminal 1 of connector "A" and terminal 1 of connector "C".

(2) Disconnect connector "B" and measure the resistance between the connectors.

Between terminal 1 of connector "A" and terminal 1 of connector "B1" ^ Continuity Between terminal 1 of connector "B2" and terminal 1 of connector "C" ^ No continuity (open) Therefore, it is found out that there is an open circuit between terminal 1 of connector "B2" and terminal 1 of connector "C".

(b) Check the voltage.

In a circuit in which voltage is applied (to the ECU connector terminal), an open circuit can be checked for by conducting a voltage check.

As shown in Fig. 4, with each connector still connected, measure the voltage between body ground and terminal 1 of connector "A" at the ECU 5V output terminal, terminal 1 of connector "B", and terminal 1 of connector "C", in that order. If the results are:

5 V: Between Terminal 1 of connector "A" and Body Ground 5 V: Between Terminal 1 of connector "B" and Body Ground 0V: Between Terminal 1 of connector "C" and Body Ground Then it is found out that there is an open circuit in the wire harness between terminal 1 of "B" and terminal 1 of "C".

pWWV

7. CHECK SHORT CIRCUIT

If the wire harness is ground shorted as in Fig. 5, locate the section by conducting a "continuity check with ground".

Z17008

Check the continuity with ground.

(1) Disconnect connectors "A" and "C" and measure the resistance between terminal 1 and 2 of connector "A" and body ground. In the case of Fig. 6:

Between terminal 1 of connector "A" and body ground ^ Continuity (short) Between terminal 2 of connector "A" and body ground ^ No continuity

Therefore, it is found out that there is a short circuit between terminal 1 of connector "A" and terminal 1 of connector "C".

Z17008

Sensor j-AVWv" ^2

(2) Disconnect connector "B" and measure the resistance between terminal 1 of connector "A" and body ground, and terminal 1 of connector "B2" and body ground.

Between terminal 1 of connector "A" and body ground — No continuity

Between terminal 1 of connector "B2" and body ground — Continuity (short) Therefore, it is found out that there is a short circuit between terminal 1 of connector "B2" and terminal 1 of connector "C". 8. CHECK AND REPLACE ECU

First check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty, so replace the ECU with a normal functioning one and check that the symptoms appear.

Example

J^qpoDQDaooaaaDocioD

J^qpoDQDaooaaaDocioD

(1) Measure the resistance between the ECU ground terminal and the body ground. Resistance: 1 Q or less

ECU Side

nr-nr

3 1=1 C

ZD 1 I C

=1 CZ1 t=

Ground

W/H Side

W/H Side

(2) Disconnect the ECU connector, check the ground terminals on the ECU side and the wire harness side for bend and check the contact pressure.

Z17808

N0383

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