1999 TOYOTA AVENSIS ECU

Diagnostic trouble code check
Making a note of and clearing of the diagnostic trouble codes displayed
Symptom confirmation
No problem symptoms
exist Problem symptoms
exist
Simulation test using the symptom
simulation methods
 Normal code displayed
 Problem symptoms exist Normal code displayed
 No problem symptoms exist Diagnostic trouble code check
Troubleshooting of problem indicated
by diagnostic trouble code Diagnostic trouble code displayed
 Problem symptoms exist
System Normal Troubleshooting of each
problem symptom
If a diagnostic trouble code was
displayed in the initial diagnostic
trouble code 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 con-
nectors (See page IN–29).
IN–22– INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
Taking into account the above points, 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.

V07268
VIBRATION METHOD: When vibration seems to be the major cause.
CONNECTORS
WIRE HARNESS
PARTS AND SENSOR1
Slightly shake the connector vertically and horizontally.
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 thorough-
ly.
Apply slight vibration with a finger to the part of the sensor
considered to be the problem cause and check that the mal-
function occurs.Shake Slightly
Swing Slightly
Vibrate Slightly
HINT:
Applying strong vibration to relays may result in open relays.
– INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN–23
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 or she may be, if he or she proceeds to troubleshoot without confirming
the problem symptoms he or she 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 condi-
tion or the vehicle at a standstill. Since vibration, heat or water penetration (moisture) is likely cause for prob-
lem 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 symp-
toms 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 symp-
toms at the same time. Refer to the problem symptoms table for each system to narrow down the possible
causes of the symptom.


B02390
HEAT METHOD: When the problem seems to occur when the suspect area is heated. 2
NOTICE:3 WATER SPRINKLING METHOD:
(1)
(2)
4 OTHER: When a malfunction seems to occur when electrical load is excessive.When the malfunction seems to occur on a rainy day or in a
high–humidity condition. 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.
Sprinkle water onto the vehicle and check to see if the malfunc-
tion occurs.
Turn on all electrical loads including the heater blower, head
lights, rear window defogger, etc. and check to see if the mal-
function occurs.ON HINT:
If a vehicle is subject to water leakage, the leaked water may
contaminate the ECU. When testing a vehicle with a water leak-
age problem, special caution must be taken.
Malfunc-
tion
Do not heat to more than 60 C (140 F). (Temperature
is limited not to damage the components.)
Do not apply heat directly to parts in the ECU. (1)
(2)
Never sprinkle water directly into the engine compart-
ment, but indirectly change the temperature and hu-
midity by applying water spray onto the radiator front
surface.
Never apply water directly onto the electronic compo-
nents. NOTICE: IN–24
– INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

Detection Item DTC No.
(See page)Trouble AreaSRS
DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is displayed during the DTC check, check the circuit listed for that code in the table
below. (Proceed to the page given for that circuit).
Warming Light
ON
ON
ON
ON
ON
ON
ON
DTC No.
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. 

Detection Item
Indicates the system of the problem or
contents of the problem. Trouble Area
Indicates the suspect area of the
problem. 
11
(DI–165)
12
(DI–170)
13
(DI–174)
14
(DI–178)
15
(DI–178)
16
airbag sensor assembly malfunction Front airbag sensor assembly (RH)
malfunction Short in D squib circuit (to ground)
Short in D squib circuit (to B)
Short in D squib circuit
Open in D squib circuit
Front airbag sensor assembly (LH)
malfunction Steering wheel pad (squib)
 Spiral cable
 Airbag sensor assembly
 Wire harness
 Front airbag sensor assembly (RH)
 Wire harness
 Front airbag sensor assembly (LH)
 Wire harness  Steering wheel pad (squib)
 Spiral cable
 Airbag sensor assembly
 Wire harness
 Steering wheel pad (squib)
 Spiral cable
 Airbag sensor assembly
 Wire harness
 Steering wheel pad (squib)
 Spiral cable
 Airbag sensor assembly
 Wire harness
Airbag sensor assembly
 Front passenger airbag sensor assembly (squib)
 Airbag sensor assembly Short in P squib circuit (to ground)ON
– INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN–25
4. DIAGNOSTIC TROUBLE CODE CHART
The inspection procedure is shown in the table below. This table permits efficient and accurate troubleshoot-
ing using the diagnostic trouble codes displayed in the diagnostic trouble code check. Proceed with trouble-
shooting in accordance with the inspection procedure given in the diagnostic chart corresponding to the
diagnostic trouble codes displayed. The Supplemental Restraint System diagnostic trouble code chart is
shown below as an example.

IN–26– INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
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.
Symptom
Suspect AreaSee page
With the ignition switch in the ACC or ON position, the SRS warning
light sometimes lights up after approx. 6 seconds have elapsed.
SRS warning light is always lit up even when ignition switch is in
the LOCK position
With the ignition switch in the ACC or ON position, the SRS warning
light does not light up.
PROBLEM SYMPTOMS TABLE
DTC is not displayed.
SRS warning light is always lit up at the time of DTC check
procedure.
DTC is displayed without Tc and E1 terminal connection.DI–294 DI–290
 Problem Symptom
Proceed with troubleshooting of each circuit in the table below.
 SRS warning light circuit
(Always lights up when ignition switch is in
LOCK position.)
 SRS warning light circuit
(Dose not light up when ignition switch is turned to
ACC or ON.)
 Tc terminal circuit
DI–288
Circuit Inspection, Inspection Order
Indicates the circuit which needs to be checked for each problem
symptom. Check in the order indicated by the numbers. Page
Indicates the page where the flow chart for each circuit
is located. 
Circuit or Part Name
Indicates the circuit or part which needs to be checked. 









B02407
WIRING DIAGRAM
DTC 13 Short in D Squib Circuit
CIRCUIT DESCRIPTION
The D squib circuit consists of the airbag sensor assembly, spiral cable and steering wheel pad.
It causes the airbag to deploy when the airbag deployment conditions are satisfied.
For details of the function of each components,see OPERATION on page RS–2.
DTC 13 is recorded when a short is detected in the D squib circuit.
DTC No.DTC Detecting Condition
Trouble Area
Short circuit between D wire harness and D wire harness of squib
D squib malfunction
Spiral cable malfunction
Airbag sensor assembly malfunctionSteering wheel pad (D squib)
Spiral cable
Airbag sensor assembly
Wire harness
 Diagnostic Trouble Code No. and Detection Item
Circuit Description
The major role and operation, etc. of the circuit
and its component parts are explained. 
Indicates the diagnostic trouble code, diagnostic
trouble code set parameter and suspect area of
the problem. 
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.
B = Black, L = Blue, R = Red, BR = Brown,
LG = Light Green, V = Violet, G = Green,
O = Orange, W = White, GR = Gray, P = Pink,
Y = Yellow
The first letter indicates the basic wire color and
the second letter indicates the color of the stripe. 
Spiral
Cable
G–R
G–Y 1
27
6D+
D–
A15
A15
D SquibAirbag Sensor
Assembly
13
– INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN–27
6. CIRCUIT INSPECTION
How to read and use each page is shown below.




 

B00972
ONTurn ignition switch ON. INSPECTION PROCEDURE
2 Check voltage at IG2 and ACC of airbag sensor assembly.
OK:
Voltage: Below 16V
Connector being checked is connected.  Indicates the condition of the connector of ECU during the check.PREPARATION:
CHECK:
Check battery and charging system.
(See charging system section)
OKNG
 Indicates the position of the ignition switch during the check.
Check from the connector back side.
(with harness)
Ignition Switch LOCK (OFF)
Ignition Switch START
LOCKIgnition Switch ON
Ignition Switch ACC
STARTON
ACC
Inspection Procedure
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.
 Indicates the place to check the voltage or resistance.
 Indicates the connector position to be checked, from the front or back side.
Connector being checked is disconnected. Check from the connector front side. (without harness)
In this case, care must be taken not to bend the terminals.
E6 Connector KNKWire Harness
E6 Connector KNK
Measure voltage between terminals IG2 and ACC of
airbag sensor assembly and body ground.
Airbag Sensor Assembly
(+)
(–)ACC IG2
 IN–28
– INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

FI0048
FI0047
FI0046
IN011–03
– INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN–29
HOW TO USE THE DIAGNOSTIC
CHART AND INSPECTION
PROCEDURE
1. CONNECTOR CONNECTION AND TERMINAL IN-
SPECTION
For troubleshooting, diagnostic trouble code charts or
problem symptom charts are provided for each circuit with
detailed inspection procedures on the following pages.
When all the component parts, wire harnesses and con-
nectors 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 per-
formed 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 inspec-
tion 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 con-
tact 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, care-
fully 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 de-
formation 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 ab-
normality 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 con-
nectors.
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 between the wire harness and body
ground, check thoroughly whether the wire harness is caught
in the body or is clamped properly.