2001 TOYOTA PRIUS Service Repair Manual

DI±250
± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check for open, short and +B short in wire harness between HV ECU terminals
(Cont1, Cont2, Cont3) and system main relay terminals (See page IN±41).
HINT:
Confirm that there is no open circuit in the wire harness. If the battery voltage is always applied to the HV
ECU Cont1, Cont2 and Cont3 terminals with the ignition ON (ºREADYº light OFF), the system main relay
has +B short.
NG Repair or replace wire harness.
OK
2 Is any of the information code 231, 232 or 233 recorded?
NO Replace HV ECU.
YES
Replace HV ECU and system main relay.

± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
DI±251
2001 PRIUS (RM778U)
CIRCUIT DESCRIPTION
If the system main relay is deposited, it might be impossible to shut down the high voltage system. Therefore,
the HV ECU checks the system main relay and stops the system if malfunction is detected.
DTC P3115 ± Information code 231, 232, 233
INF. Code.Detecting ConditionTrouble Area
231System main relay + terminal deposited
232System main relay ± terminal deposited
System main relay

HV ECU233System main relay + & ± terminal deposited
HV ECU
INSPECTION PROCEDURE
If any of these information codes is output, replace the system main relay.
If one of the information codes above and any of the information codes 224 ± 229 are recorded at the same
time, also replace the HV ECU.

DI±252
± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
2001 PRIUS (RM778U)
DTC P3120 HV Transaxle Malfunction
CIRCUIT DESCRIPTION
The HV ECU checks the energy balance and detects abnormality if the magnetism of the motor or generator
greatly decreases.
HINT:

When using an OBD scan tool other than TOYOTA hand±held tester, check all the steps.

When using TOYOTA hand±held tester, confirm the information code and check it.
DTC P3120 ± Information code 234, 235, 236, 237
INF. Code.Detecting ConditionTrouble Area
234Small reduction of motor magnetism
HV transaxle (motor)
235Large reduction of motor magnetism

HV transaxle (motor)

System main relay
236Small reduction of generator magnetism
HV transaxle (generator)
237Large reduction of generator magnetism

HV transaxle (generator)

System main relay
INSPECTION PROCEDURE
1 Is DTC of HV battery ECU being output?
YES Check applicable DTC.
NO
2 Turn the ignition switch to ST(ON) and check if malfunction occurs again.
NO Replace system main relay.
YES
Replace HV transaxle motor or generator.
DI837±02

± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
DI±253
2001 PRIUS (RM778U)
CIRCUIT DESCRIPTION
The HV ECU detects the malfunction of the transmission system. Judging from a malfunction symptom, it
records one of the four information codes.
DTC P3120 ± Information code 239, 240, 241, 242
INF. Code.Detecting ConditionTrouble Area
239Shaft damaged
240Generator lockedHV t l241Torque limiter sliding
HV transaxle
242Planetary gear locked
INSPECTION PROCEDURE
When Information code 239 in stored, check that the connector of the crankshaft position sensor is properly
connected. If disconnected, the code 239 may be stored.
If any of these information codes is output, replace the defective part inside the HV transaxle.

A14122
Motor Generator No. 2Hybrid Vehicle
Control ECU
MSNG
MSN
MCS
MCSG
MRF
MRFG5
M3
2
M3
3
M3
6
M3
1
M3
4
M3G
RMSNG
MSN
MCS
MCSG
MRF
MRFG P
L
B
W20
H10
13
H10
14
H10
21
H10
19
H10
18
H10 DI±254
± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
2001 PRIUS (RM778U)
CIRCUIT DESCRIPTION
The HV ECU checks the motor resolver signal voltage and circuit impedance to detect malfunction.
DTC P3120 ± Information code 243, 245
INF. Code.Detecting ConditionTrouble Area
243Motor resolver inter±phase short
HV transaxle
245Open or short in motor resolver circuit

HV transaxle

Wire harness
WIRING DIAGRAM

± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
DI±255
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check for open and short in wire harness between HV transaxle and HV ECU
(See page IN±41).
Terminals for checking open and short:
MG2 TerminalsHV ECU Terminals
MSNGMSNG
MSNMSN
MCSMCS
MCSGMCSG
MRFMRF
MRFGMRFG
NG Repair or replace wire harness.
OK
Check for open in motor resolver or inter±phase short and then replace HV transaxle motor.
Check motor resolver (See page HV±40).