DI–132
DIAGNOSTICS
–
ENGINE
DI7DK–01
ECM Power Source Circuit
CIRCUIT INSPECTION
When the ignition switch is turned on, battery positive voltage is applied to IG2 Relay, terminal IGSW of the
ECM and the EFI main relay (Marking: EFI MAIN) control circuit in the ECM sends a signal to terminal MREL
of the ECM switching on the EFI main relay.
This signal causes current to flow to the coil, closing the contacts of the EFI main relay and supplying power
to terminals +B of the ECM.
If the ignition switch is turned off, the ECM continues to switch on the EFI main relay for a maximum of 2
seconds for the initial setting of the IAC valve.
WIRING DIAGRAM
Engine Room R/B
FL Block
EFI MAIN Relay
EFI1
1
2
1
B–Y
2
W–B
W–B
IG2
1
2
B–W
1
AM2
1
2
ECM
W–R
1
2
2
2
10
IC1
5
3
2
2
1
IG2 Relay
2
1
5
B
16
E2
+B
GR
21
E3
MREL
8
E2
IGSW
17
E4
E1
2
3
2
2
R–W
B–R
I10
IC1 2
Ignition SW
W–R
R–W
6
5
1
BR
B–L
FL Main
Battery
EA
EB
A13049
2000 MR2 (RM760U)
AuthorĂ:
DateĂ:
296
DI–133
DIAGNOSTICS
–
ENGINE
INSPECTION PROCEDURE
1
Check voltage between terminals +B and E1 or ECM connectors.
ON
+B
E1
(–)
(+)
BE6653
A09373
A10563
PREPARATION:
(a) Disconnect the ECM with connector from body panel
(See page SF–62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals +B and E1 of the ECM
connectors.
OK:
Voltage: 9 – 14 V
OK
Proceed to next circuit inspection shown on
problem symptoms table (See page DI–21).
NG
2
Check for open in harness and connector between terminal E1 of ECM connector
and body ground (See page IN–28).
NG
Repair or replace harness or connector.
OK
3
Check voltage between terminal IGSW of ECM connector and body ground.
IGSW
(–)
BE6653
A09636
(+)
A09702
PREPARATION:
(a) Disconnect the ECM with connector from body panel
(See page SF–62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminal IGSW of the ECM connector and body ground.
OK:
Voltage: 9 – 14 V
OK
Go to step 6.
NG
2000 MR2 (RM760U)
AuthorĂ:
DateĂ:
297
DI–134
DIAGNOSTICS
4
–
ENGINE
Check IG2 fuse.
PREPARATION:
Remove the IG2 fuse from the FL block.
CHECK:
Check the continuity of the IG2 fuse.
OK:
Continuity
FL Block
NG
IG2 Fuse
A12786
Check for short in all harness and components
connected to IG2 fuse (See attached wiring diagram).
OK
5
Check IG2 relay (See page IG–7).
NG
Replace IG2 relay.
OK
6
Check AM2 fuse.
PREPARATION:
Remove the AM2 fuse from the FL block.
CHECK:
Check the continuity of the AM2 fuse.
OK:
Continuity
FL Block
NG
AM2 Fuse
A12786
Check for short in all harness and components
connected to AM2 fuse (See attached wiring diagram).
OK
2000 MR2 (RM760U)
AuthorĂ:
DateĂ:
298
DI–135
DIAGNOSTICS
7
–
ENGINE
Check ignition switch (See page BE–15).
NG
Replace ignition switch.
OK
Check and repair harness and connector between battery and ignition switch, and ignition switch and ECM.
8
Check voltage between terminal MREL of ECM connector and body ground.
MREL
(–)
(+)
BE6653
A09637
A09703
PREPARATION:
(a) Disconnect the ECM with connector from body panel
(See page SF–62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminal MREL of the ECM connector and body ground.
OK:
Voltage: 9 – 14 V
NG
Check and replace ECM (See page IN–28).
OK
9
Check EFI1 fuse (See page DI–123, step 2).
NG
Check for short in all harness and components
connected to EFI1 fuse (See attached wiring
diagram).
OK
10
Check EFI main relay (Marking: EFI MAIN) (See page SF–44).
NG
Replace EFI main relay.
2000 MR2 (RM760U)
AuthorĂ:
DateĂ:
299
DI–136
DIAGNOSTICS
–
ENGINE
OK
11
Check for open and short in harness and connector between terminal MREL of
ECM and body ground (See page IN–28).
NG
Repair or replace harness or connector.
OK
Check and repair harness or connector between EFI1 fuse and battery.
2000 MR2 (RM760U)
AuthorĂ:
DateĂ:
300