2001 TOYOTA PRIUS Service Repair Manual

± DIAGNOSTICSENGINE
DI±155
2001 PRIUS (RM778U)
7 Check crankshaft position sensor and camshaft position sensor
(See page IG±1).
NG Repair or replace.
OK
8 Check throttle control motor and throttle position sensor (See page SF±24).
NG Repair or replace.
OK
Chack and replace ECM (See page IN±41).

A14058
ECM
+B 4
E8
BatteryW±RG±R
MREL 25 EFI Relay
I15 Ignition
SW EFI
IGSW 6
IE 1B35
AM2E9
J24 J25
J1
J/CE10 B
9 3
B
2C1 2
2G
24
A F121 3
1K 1F12 1A
1J 2
7 1
W±BW±R
B±W
B±G Engine Room J/B
F18
FL
Block
No. 2IA2
FL Block No. 19G±R
J7
J/C
B±W AM2 IG2
J/C Instrument
Panel J/B
F13 1
A
A W±BCB
MAIN
1 DI±156
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
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
DI7DK±02

A13635
ON
+B
E1
(±) (+)
A13636
IGSW
(+) (±)
± DIAGNOSTICSENGINE
DI±157
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check voltage between terminals +B and E1 or ECM connectors.
PREPARATION:
(a) Remove the ECM with connector still connected (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±22).
NG
2 Check for open in harness and connector between terminal E1 of ECM connector
and body ground (See page IN±41).
NG Repair or replace harness or connector.
OK
3 Check voltage between terminal IGSW of ECM connector and body ground.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminal IGSW of the ECM con-
nector and body ground.
OK:
Voltage: 9 ± 14 V
OK Go to step 6.
NG

A13630
Engine Room J/B
AM2 Fuse
DI±158
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
4 Check AM2 fuse.
PREPARATION:
Remove the AM2 fuse from the engine room J/B.
CHECK:
Check the continuity of the AM2 fuse.
OK:
Continuity
NG Check for short in all harness and components
connected to AM2 fuse (See attached wiring dia-
gram).
OK
5 Check ignition switch (See page BE±16).
NG Replace ignition switch.
OK
Check and repair harness and connector be-
tween battery and ignition switch, and igni-
tion switch and ECM.

A14004
MREL
(+) (±)
A13630
Engine Room J/B
EFI Fuse
± DIAGNOSTICSENGINE
DI±159
2001 PRIUS (RM778U)
6 Check voltage between terminal MREL of ECM connector and body ground.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminal MREL of the ECM con-
nector and body ground.
OK:
Voltage: 9 ± 14 V
NG Check and replace ECM (See page IN±41).
OK
7 Check EFI1 fuse.
PREPARATION:
Remove the EFI fuse from the engine room J/B.
CHECK:
Check continuity of EFI fuse.
OK:
Continuity
NG Check for short in all harness and components
connected to EFI1 fuse (See attached wiring
diagram).
OK
8 Check EFI main relay (Marking: EFI MAIN) (See page SF±37).
NG Replace EFI main relay.
OK