engine TOYOTA PRIUS 2001 Service Repair Manual

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.

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

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

± DIAGNOSTICSENGINE
DI±163
2001 PRIUS (RM778U)
OK Go to step 5.
NG
Check for open in harness and connector between EFI main relay and circuit opening relay (Mark-
ing: C/OPN), circuit opening relay and ECM (See page IN±41).
5 Check fuel pump (See page SF±6).
NG Repair or replace fuel tank assembly.
OK
6 Check for open in harness and connector between circuit opening relay and fuel
pump and body ground (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page IN±41).

A14005B10046
A14006
ON
FC
Fuel Inlet Hose
OFF
ON
DI±164
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
OBD II scan tool (excluding TOYOTA hand±held tester):
1 Check operation of fuel pump.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Turn the ignition switch ON.
CHECK:
(a) Connect between terminal FC of the ECM connector and
body ground.
(b) Check for fuel pressure in the fuel inlet hose when it is
pinched off.
OK:
There is pressure in fuel inlet hose.
HINT:
At this time, you will hear a fuel return flowing noise.
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

± DIAGNOSTICSENGINE
DI±165
2001 PRIUS (RM778U)
4 Check voltage between terminal FC of ECM and body ground
(See page DI±161).
OK Go to step 5.
NG
Check for open in harness and connector between EFI main relay and circuit opening relay (Mark-
ing: C/OPN), circuit opening relay and ECM (See page IN±41).
5 Check fuel pump (See page SF±6).
NG Repair or replace fuel tank assembly.
OK
6 Check for open in harness and connector between circuit opening relay and fuel
pump and body ground (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page IN±41).

A14037
Combination MeterECM
Instrument Panel J/B
W
BatteryE10 IG1 Relay
6
J11
J/C IG1C11
C10
ID DC/DCG±R
2A
A 5
W
W±B
F114
3GAUGE
Ignition SW 22
2 3B±Y
21
2 1
1 1
MAINL
AM1
B±G4
FL Block No. 1FL Block No. 2 F1312D
2B 2K 2H
86 5
AM1
W±G
MIL
DI±166
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
MIL Circuit Malfunction
CIRCUIT DESCRIPTION
If the ECM detects trouble, the MIL lights up. At this time, the ECM records a DTC in memory.
HINT:
When the ignition switch is ON and ºREADYº indicator light is OFF, the bulb check of the ºMILº is performed
(ºMILº is ON).
When ºMILº is ON, but the DTC of the engine is not memorized, it may be because of HV control system
abnormality, so check HV control system beforehand.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
Troubleshoot in accordance with the chart below for each trouble symptom.
MIL does not light up
Start inspection from step 1 in case of using TOYOTA hand±held
tester and start from step 2 in case of not using TOYOTA hand±
held tester
MIL remains on
After inspection of step 3, start inspection from step 4 in case of
using TOYOTA hand±held tester and start from step 5 in case of
not using TOYOTA hand±held tester
DI6MN±03

± DIAGNOSTICSENGINE
DI±167
2001 PRIUS (RM778U)
1 Inspect diagnosis (normal mode, check mode) (See page DI±3).
OK Check and replace ECM (See page IN±41).
NG
2 Check MIL.
See combination meter troubleshooting on page BE±2.
NG Repair or replace bulb or combination meter as-
sembly.
OK
3 Check that ECM connectors are securely connected to ECM.
NO Connect connector to ECM.
YES
Check for open circuit in harness and connector between combination meter and ECM (See
page IN±41).
4 Check operation of MIL (See step 1).
OK Check and replace ECM (See page IN±41).
NG

DI±168
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
5 Is any DTC output?
Check DTC on page DI±14.
YES Repair circuit indicated by output code.
NO
6 Check IG1 relay (Marking: IG1).
NG Replace IG1 relay.
OK
Check for short circuit in harness and con-
nector between DLC3 and ECM (See page
IN±41).

A14038
W±B 13TC E9
TC
CG D2 DLC3
4P±B
Instrument Panel J/B6 2
2K 2D ID1
AECM
ID W±BA J24
J/CE
W±BP±B
J11
J/C J26 J/C
P±B
A E
W±B 8 8P±BJ16 J/C
C
C
F08565
CG
(±)
(+) ON
TC
± DIAGNOSTICSENGINE
DI±169
2001 PRIUS (RM778U)
TC Terminal Circuit
CIRCUIT DESCRIPTION
Terminal TC and CG are located in the DLC3. When connecting these terminals, DTCs in normal mode or
test mode can be read through the MIL flashing in the combination meter.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

Even though terminal TC is not connected with terminal CG, the MIL blinks.

For the above phenomenon,an open or short in the wire harness, or malfunction inside the ECM is the
likely cause.
1 Check voltage between terminals TC and CG of DLC3.
PREPARATION:
Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals TC and CG of the
DLC3.
OK:
Voltage: 9 ± 14 V
OK Check and replace ECM (See page IN±41).
NG
DI7DL±02