Toyota ZZT230 series, Repair Manual

Page: 27 / 821

IN-22
2. SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the CELICA 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 CELICA.
Sy•tem
Diagnostic
T rouble Input Signal
Check
Diagnostic Test
Code
Check
(Sensor
Check} Mode (Active
Test)
.
......
0
{with Check
0
0
Mode)
Automatic
Transaxte
{U240E) 0
(with
Check
0
Mode)
Automatic
Transaxle
(U341 E) 0
(with
Check 0
Mode)
Anti-LOCk
Brake System
with Electror*:
Brake
Force Distribution
(
EB D ) 0 0
0
SUpplemental Restraint System
0
Cn.ise Control
System 0
0
.
.
.
In diagnostic trouble code check, it 1s very Important to detenmne whether the problem indicated by the d1ag·
nestle 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 confinnation 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
t
r
o
ubl
esh
oo
t
i
ng
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.
DIAGNQ&TIC TROUBLE CODE CHECK PROCEDURE
Diagnostic
Trouble
C
o
n
f
i
r
ma
t
i o
n
Diagnostic Trouble
Coda Check (Make a
Problem Condition
nota
of and than
claar)
of Symptoms Coda Check
Diagnostic Trouble
Problem symptoms Same d
i
ag nos
t
i c
Problem is still occurring in the diagnostic
Code
Display
e
x
is
t
trouble code
is
c ir
c
ui t
d
i
sp
l
ay
ed
Normal code is
The problem is still occurring in a place
d
i sp
l
ay
e d
other than in the diagnostic circuit
(The diagnostic trouble code displayed
first is either for a past problem or it is a
secondary problem)
The problem occurred in the diagnostic
symptoms exist
circuit in the past
Normal
Code symptoms Normal code is
The problem is still occurring in a place
e
x
t
s t di s p la y
ed
other than in the diagnostic circuit
Normal code Is The problem occurred in a place other
symptoms exist displayed than in the diagnostic circuit in the past