fuse TOYOTA CELICA 1987 Service User Guide

EFI SYSTEM - Diagnosis System
. .
DIAGNOSIS SYSTEM
__ --
FL25
(MA)
The ECU contains a built-in self-diagnosis system by which
troubles with the engine signal network are detected and a
“CHECK ENGINE” warning light on the instrument panel
flashes,
By analyzing various signals as shown in the later table (See
pages Fl-30, 31) the Electronic Control Unit (ECU) detects
system malfunctions which are related to the various operating
parameter sensors or to the actuator. The ECU stores the
failure until the diagnosis system is cleared by removing the EFI
fuse with the ignition switch off.
A “CHECK ENGINE” warning light on the instrument panel
informs the driver that a malfunction has been detected.
The light goes out automatically when the malfunction has
been cleared.
The diagnostic code can be read by the number of the blinks of
the “CHECK ENGINE” warning light when T and El are short-
circuit.
(MS)
The ECU contains a built-in self-diagnosis system by which
troubles with the engine signal network are detected and a
“CHECK ENGINE” warning light on the instrument panel
flashes.
By analyzing various signals as shown in the later table (See
page FI-32) the Electronic Control Unit (ECU) detects system
malfunctions which are related to the various operating
parameter sensors or to the actuator. The ECU stores the
failure until the diagnosis system is cleared by removing the EFI
fuse with the ignition switch off.
In the ECU, a test mode function has been added to the func-
tions of the self-diagnosis system of the previous diagnosis
mode (normal mode) for the purpose of detecting malfunctions
such as poor contact which are difficult to detect in the normal
mode. This function fills up the self-diagnosis system. The test
mode can be implemented by the technician to follow the pro-
cedures of appropriate check terminal connection and opera-
tion described in later (See page FI-28).
In the normal mode, the self-diagnosis system monitors 14
items, indicated by the codes except for code No. 51 as shown
in FI-32. A “CHECK ENGINE” warning light on the instrument
panel informs the driver that a malfunction has been detected.
The light goes out automatically when the malfunction has
been cleared.
The diagnostic code can be read by the number of the blinks of
the “CHECK ENGINE” warning light when TEl and El are
short-circuited.

EFI SYSTEM - Diagnosis System FI-29
MS EFI 15iA
LHD
EFI 15A
EFI 15A
R16C
FI26:
CANCELLING OUT DIAGNOSTIC CODE
1.
2. After repair of the trouble area, the diagnostic code
retained in memory by the ECU must be cancelled out by
removing the EFI fuse 15A for 30 seconds or more,
depending on ambient temperature (the lower the tem-
perature, the longer the fuse must be left out) with the
ignition switch off.
NOTE:
l Cancellation can also be done by removing the battery”
negative (-1 terminal, but in this case other memory
systems (clock etc.) will also be cancelled out.
l If the diagnostic code is not cancelled out, it will be
retained by the ECU and appear along with a new code
in event of future trouble.
l If it is necessary to work on engine components requir-
ing removal of the battery terminal, a check must first
be made to see if a diagnostic code has been recorded.
After cancellation, road test the vehicle to check that a
“normal” code is now read on the “CHECK ENGINE”
warning light.
If the same diagnostic code is still indicated, it means that
the trouble area has not been repaired thoroughly.
DIAGNOSIS INDICATION
(I) When 2 or more codes are indicated, the lowest number
(code) will appear first.
However, no other code will appear along with code No.
11.
(2) All detected diagnostic codes, except 51 and 53, will be
retained in memory by the ECU from the time of detection
until cancelled out.
(3) Once the malfunction is cleared, the “CHECK ENGINE”
warning light on the instrument panel will go out but the
diagnostic code(s) remain stored in ECU memory (except
for codes 51 and 53).

EFI SYSTEM
- Diagnosis System
FI-33
INSPECTION OF DIAGNOSIS .ClRCUlT
._
Fuse IGN
“CHECK ENGINE”
Fl291
1.
I Dose “CHECK ENGINE” warning light come
on when ignition switch is at ON?
l-l YES System Normal
Does “CHECK ENGINE” warning light come Check wiring between
on when ECU terminal W is grounded to the
YES ECU terminal El and body OK Try another
body? - ground. __c ECU
+NO
Check bulb, fuse and wiring between ECU and
ignition switch. + SAD
Repair or replace
Does “CHECK ENGINE” warning light go off
when the engine is started? YES
. System Normal
NO
Check wiring between ECU and
“CHECK ENGINE” warning light.
1 OK
Is there diagnostic code output when check
connector terminals T(MA) or TEl (MS) and
El are short circuited? t
Check wiring between ECU terminal T and check
NO connector terminal T(MA) or TEl (MS), and ECU
* terminal El and check connector terminal El.
I I
I I
YES
Does “CHECK ENGINE” warning light go out NO
after repair according to malfunction code? ) Further repair required.
&
System OK Cancel out diagnostic code.

-34 EFI SYSTEM - Troubleshooting with Volt/dhmmeter (MA)
. .
TROUBLESHOOTING WITH
VOLT/OHMMETER (MA)
OTE: The following troubleshooting pro-
sdures are designed for inspection of each separ-
te system, and therefore the actual procedure
lay vary somewhat. However, troubleshooting
hould be performed refering to the inspection
lethods described in this manual. The following troubleshooting procedures are
based on the supposition that the trouble lies in
either a short or open circuit in a component out-
side the computer or a short circuit within the
computer.
Jefore beginning inspection, it is best to first make
3 simple check of the fuses, fusible links and the
:ondition of the connectors. If engine trouble occurs even though proper
operating voltage is detected in the computer con-
nectar, then it can be assumed that the ECU is
faulty and should be replaced.
LOCATION OF FUSES AND FUSIBLE LINKS
No.
r 1 Relay Block (RHD)
I
61 I
No. 1 Relay Block (LHD)
Fuse IGN’ Fusible Link
ALT
(7M-GE) 1.259
(7M-GTE) 1 OCjA Fuse IdN 7.5A
EFI Main Relay
No. 2
Relay Block
Fusible Link
AM2 30A Fuse EFI 15A

FI-40 EFI SYSTEM - Troubleshooting with Volt/Ohmmeter (MA)
Voltmeter
Voltmeter
Ed ., + . IG S/W - El --
1
0 There is no voltage between ECU terminals IG S/W and El.
(IG S/W ON1
1
CD Check that there is voltage between ECU terminal IG S/W and
body ground. (IG S/W ON)
NO OK
Check wiring between ECU terminal El and body
ground.
’ OK
Try another ECU.
Check fuse, fusible links and BAD
Repair or replace.
. M-REL - El
0 There is no voltage between ECU terminals M-REL and El.
(IG S/W ON)
1
0 Check that there is voltage between ECU terminal M-REL and
body ground. (IG S/W ON)
NO OK
Check wiring between ECU terminal El and body
ground.
OK
Try another ECU.
I Replace or repair.
Check EFI main relay and wiring
harness.
I BAD
c Replace.
4
I Try another ECU.
I

EFI SYSTEM - Troubleshooting with Volt/Ohmmeter (MA) FI-41
. +B (+Bl) - El
I 0
There is no voltage between ECU terminals +B
(IO SAN ON)
I
0 Check that there is voltage between ECU terminal +B (+Bl 1
and body ground. (IO S/w ON)
I I
NO OK
Check wiring between ECU terminal El and body ground.
OK
BAD
Try another ECU.
I Replace or repair.
1 I I
I
Check fuse, fusible links and wiring BAD
harness.
H Repair or replace.
I
I I I I I
1 OK I I I 1 Check EFI main relay.
(See page FI-1 12)
OK BAD
* Replace.
I
Refer to M-REL - El trouble
section.
I

EFI SYSTEM - Troubleshooting with Volt/Ohmmeter (MA)
JO. Terminals Trouble Condition
S-m Voltage
No. IO
EOl
5 No. 20 -
E02 No voltage Ignition switch ON 9-14v
No. 30
Fusible
Link
8 MAIN 2.OL
-T
T
Battery f
-
I
= -“No. 10
I c
FIZE
Ignition Switch ECU
No. 2C
Voltmeter
A Solenoid Resistor
nr R?r
0 There is no voltage between ECU terminal No. 10, No. 20
and/or No. 30 and EOl or E02. (IO S/W ON)
1.
0 Check that there is specified voltage between resistor terminal
+B and body ground. STD voltaae: 9 - 14 V
1 NO 1
.
Check fuse, fusible links BAD
and ignition switch. - Repair or replace.
I i
1 OK I
I I ,
1
Check wiring between
resistor and battery. BAD
- Repair or replace.
Check that there is specified voltage between resistor terminal
@ (No. IO, No. 20 or No. 30) and body ground.
j ‘,.“.““!
I 0
Check resistance of magnetic coil in
each lniector. I 1 Replace resistor.
I
I . J I I

EFI SYSTEM - Troubleshooting with Volt/Ohmmeter (MA) FI-53
No.
Terminals
Trouble Condition
STD Voltage
11 ISCl - ISC4 - El No voltage
Ignition switch ON
g-14v
Fusible
Link EFI Main Relay
ISC Valve
Fuse
EFI 15A
Fusible
Link
h MAIN 2.OL AM2 30A
I
, ECU
ISCI
ISC2
ISC3
ISC4
+B
+Bl
M-REL
01
doltmeter
@I
Bl
V
PI
Y
I Fk-n12
Fl16431
0 There is no voltage between ECU terminals ISCl - ISC4 and
El. (IG S/W ON1
0 check that there is voltage between ECU terminal +B (+Bl)
and body ground. UG S/W ON)
OK
1 Check wiring between ECU terminal El and body ground. 1
I OK
0 Check ISC valve.
(See page.FI-I 08)
, 1 Repair or replace. )
I
Replace ISC
I I Check wiring between ECU and EFI
valve.
main relay.
I

EFI SYSTEM - Troub!eshoo$ng with Volt/Ohmmeter (MA)
. .
JO. Terminals
12 W - El Trouble
No voltage Condition
Nq @uble, (“CHECK” engine warning
light off) and engine running STD Voltage
s-14v
FUSE
GAUGE 7.5A
i
f “CHECK ENGINE”
Wahiing Light
Combination Mete W
El
FlO7
Joltmeter
EL v “_
Fl1251
1
Voltmeter
FH25C
. .
~0 There is no voltage between ECU terminals W and El.
(Idlin$
,
.
I 0
Check that there is voltage between ECU terminal W and
I
hod
Q;
0 Check wiring between ECU terminal El and body
Check GAUGE fuse (7.5A) and “CHECK
ENGINE” warning light.
I I
I Repair or replace.
I
1
Check wiring between ECU terminal BAD
*
W and fuse. Repair or replace.
I I
1 I

EFI SYSTEM - Troubleshooting with Volt/Ohmmeter (MS) FI-57
-.
TROUBLESHOOTING WITH
VOLT/OHMMETER (MS)
NOTE: The following troubleshooting pro-
cedures are designed for inspection of each separ-
ate system, and therefore the actual procedure
may vary somewhat.. However, troubleshooting
should be performed refering to .the inspection
methods described in this manual. .._
Before beginning,inspection, it is best to first make
a simple check of the fuses, fusible links and the The following troubleshooting procedures are
based on the supposition that the trouble ‘lies in
either a short or open circuit in a component out-
side the computer or a short circuit within the
computer.
If engine trouble occurs even though proper.
operating voltage is detected in the computer con-
nector, then it can be assumed that the ECU is
faulty and should be replaced.
LOCATIoN- OF FUSES AND FUSIBLE LINKS
condition of the connectors.
Junction Block and Relay Block Cassettes