TOYOTA PRIUS 2001 Service Repair Manual
Manufacturer: TOYOTA, Model Year: 2001, Model line: PRIUS, Model: TOYOTA PRIUS 2001Pages: 1943, PDF Size: 18.26 MB
Page 751 of 1943

± DIAGNOSTICSENGINE
DI±153
2001 PRIUS (RM778U)
DTC P3190 Poor Engine Power
DTC P3191 Engine dose not Start
CIRCUIT DESCRIPTION
From the HV ECU, the ECM receives data such as power output required for the engine (required output),
estimated torque produced by the engine (estimated torque), engine RPM of control target (target RPM),
whether the engine is in start mode or not. Then, based on the required output and target RPM, the ECM
calculates a target torque that is to be produced by the engine and compares it with the estimated torque.
If the estimated torque is very low compared with the target torque, or the engine start mode continues at
the engine RPM or for the duration calculated by water temperature, an abnormal condition is detected.
DTC No.DTC Detecting ConditionTrouble Area
P3190
Following condition (a) to (e) continues at a fixed engine RPM
or a fixed length of time:
(a) Communication with HV ECU is normal.
(b) Engine RPM is a fixed value or more.
(c) Engine star mode is not active.
(d) Target torque is a fixed value or more.
(e) Ratio of estimated torque against target torque is less than
20 %.
Air induction system
Throttle body
Fuel pressure
Engine
Air flow meter
Out of fuel
Wt t
P3191
Following condition (a) to (c) continues at a fixed engine RPM
or for a fixed length of time:
(a) Vommunication with HV ECU is normal.
(b) Engine RPM is a fixed value or more.
(c) Engine start mode is active.Water temp. sensor
Crankshaft position sensor
Camshaft position sensor
ECM
WIRING DIAGRAM
Refer to DTC P1636 on page DI±146.
INSPECTION PROCEDURE
1 Are there any other codes begin output?
YES Go to relevant DTC chart.
NO
DI7T6±01
Page 752 of 1943

DI±154
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
2 Check remaining amount of fuel.
NG Supply fuel.
OK
3 Check air induction system (See page SF±1).
NG Repair or replace.
OK
4 Check for umusual noise or vibration when starting engine or racing.
NG Repair or replace.
OK
5 Check fuel pressure (See page SF±6).
NG Check and repair fuel pump and fuel pipe line
(See page SF±19).
OK
6 Check air flow meter (See page SF±22) and engine coolant temp. sensor
(See page SF±49).
NG Repair or replace.
OK
Page 753 of 1943

± 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).
Page 754 of 1943

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
Page 755 of 1943

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
Page 756 of 1943

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.
Page 757 of 1943

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
Page 758 of 1943

DI±160
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
9 Check for open and short in harness and connector between terminal MREL of
ECM and body ground (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and repair harness or connector be-
tween EFI1 fuse and battery.
Page 759 of 1943

A14059
B±G
EFICIR OPN
Relay
MREL Engine Room J/B
1A
B
AECM
FC
F16
Fuel
Pump
IE 5
FL Block No. 1
MAIN
F12
BatteryE8
E9 259
W±B
J17
J/C J1
J/C
IG J7
J/C IA1
IA2
W±B
AA A W±B G±R B±R
F18
FL Block No. 2EFI
Relay
1K 1F
1B10
1F
2 121
3
2
1
3
3
1
11 52 1
3
F13G±R
B±R
7 14
4
G±R
± DIAGNOSTICSENGINE
DI±161
2001 PRIUS (RM778U)
Fuel Pump Control Circuit
CIRCUIT DESCRIPTION
When starting the engine with ignition switch:
HV ECU receives ST signal and decides to start the engine, and send the signal of the engine start prior
signal to the engine ECU by the communicatio between the engine ECU and HV ECU.
Engien ECU receives that signal and turns ON the circuit opening relay slightly earlier, then turns the fuel
pump.
When starting the engine in an intermittent operation:
With the cranking by MG1, NE signal comes in immediately, so the engine ECU receives the generation of
NE signal and turns the fuel pump. (At this time, no refernce of the communication from HV ECU)
When stopping the fuel pump:
When the signal to stop the engine comes in to the engine ECU from HV ECU from HV ECU side, the fuel
pump stops.
At the time of the fuel cut opetation such as deceleration by the engine brake, the fuel pump stops.
WIRING DIAGRAM
DI7T7±01
Page 760 of 1943

A14007
FC ON
(±) (+) DI±162
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
TOYOTA hand±held tester:
1 Connect TOYOTA hand±held tester and check operation of fuel pump (See page
DI±3).
OK Proceed to next circuit inspection shown on
problem symptoms table (See page DI±22).
NG
2 Check for ECM power source circuit (See page DI±156).
NG Repair or replace.
OK
3 Check circuit opening relay (Marking: C/OPN) (See page SF±38).
NG Replace circuit opening relay.
OK
4 Check voltage between terminal FC of ECM 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 FC of the ECM and body
ground.
OK:
Voltage: 9 ± 14 V