2001 TOYOTA PRIUS check engine

± DIAGNOSTICSENGINE
DI±11
2001 PRIUS (RM778U)
NG Proceed to page SF±6 and continue to trouble-
shoot.
OK
7 Check for spark.
PREPARATION:
(a) Remove the ignition coil (See page IG±5).
(b) Remove the spark plug.
(c) Install the spark plug to ignition coil and connect the ignition coil connector to ignition coil.
(d) Disconnect the injector connector.
(e) Be sure to ground the screw of the spark plug securely.
CHECK:
Check if spark occurs while engine is being cranked.
NOTICE:

Do not crash the electrode gap.

To prevent excess fuel being injected from the injectors during this test, don't crank the engine
for more than 5 ± 10 seconds at a time.
NG Proceed to page IG±1 and continue to trouble-
shoot.
OK
Proceed to problem symptoms table on page
DI±22.

DI6UT±02
DI±14
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DIAGNOSTIC TROUBLE CODE CHART
HINT:
Parameters listed in the chart may not be exactly the same as your reading due to the type of instru-
ment or other factors.
If a malfunction code is displayed during the DTC check in check mode, check the circuit for that code
listed in the table below. For details of each code, turn to the page referred to under the ''See page
'' for the respective ''DTC No.'' in the DTC chart.
When the ignition switch is ON and ºREADYº indicator light is OFF, the bulb check of the ºMILº is per-
formed (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.
SAE CONTROLLED:
DTC No.Detection ItemTrouble AreaMIL*1Memory
P0100
(DI±23)Mass Air Flow Circuit Malfunc-
tionOpen or short in mass air flow meter circuit
Mass air flow meter
ECM

P0101
(DI±27)Mass Air Flow Circuit Range/
Performance ProblemMass air flow meter
P0110
(DI±28)Intake Air Temp. Circuit Malfunc-
tionOpen or short in intake air temp. sensor circuit
Intake air temp. sensor (built into mass air flow meter)
ECM

P0115
(DI±32)Engine Coolant Temp. Circuit
MalfunctionOpen or short in engine coolant temp. sensor circuit
Engine coolant temp. sensor
ECM

P0116
(DI±36)Engine Coolant Temp. Circuit
Range/Performance ProblemCooling system
Engine coolant temp. sensor
P0120
(DI±38)Throttle/Pedal Position Sensor/
Switch ºAº Circuit MalfunctionOpen or short in throttle position sensor circuit
Throttle position sensor
ECM

P0121
(DI±43)Throttle/Pedal Position Sensor/
Switch ºAº Circuit Range/Perfor-
mance ProblemThrottle position sensor
ECM
P0125
(DI±44)Insufficient Coolant Temp. for
Closed Loop Fuel Control
Open or short in heated oxygen sensor (bank 1 sensor 1)
circuit
Heated oxygen sensor (bank 1 sensor 1)
Air induction system
Fuel pressure
Injector
Gas leakage on exhaust system
ECM

P0128
(DI±49)Thermostat Malfunction
Thermostat
Cooling system
Water temperature
ECM

P0130
(DI±50)Heated Oxygen Sensor Circuit
Malfunction (Bank 1 Sensor 1)
(Except Calif.)
Open or short in heated oxygen sensor circuit
Heated oxygen sensor
Air induction system
EGR system
Fuel pressure
Injector
ECM


DI±16
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)P0340
(DI±76)
Camshaft Position Sensor Cir-
cuit Malfunction
Open or short in camshaft position sensor circuit
Camshaft position sensor
Camshaft timing pulley
ECM

P0420
(DI±78)Catalyst System Efficiency Be-
low Threshold (Bank 1)
Gas leakage on exhaust system
Open or short in heated oxygen sensor circuit
Heated oxygen sensor
Three±way catalytic converter

P0440
(DI±81)Evaporative Emission Control
System Malfunction
Hose or tube cracked, hole, damaged or loose seal
Fuel tank cap incorrectly installed
Fuel tank cap cracked or damaged
Vacuum hose cracked, hole, blocked,damaged or discon-
nected
Fuel tank cracked, hole or damaged
Charcoal canister cracked, hole or damaged
Open or short in vapor pressure sensor circuit
Vapor pressure sensor
Fuel tank over fill check valve cracked or damaged
ECM

P0441
(DI±87)Evaporative Emission Control
System Incorrect Purge Flow
Vacuum hose cracked, hole, blocked damaged or discon-
nected
Open or short in vapor pressure sensor circuit
Vapor pressure sensor
Open or short in VSV circuit for EVAP
VSV for EVAP
P0446
(DI±87)Evaporative Emission Control
System Vent Control Malfunction
VSV for EVAP
Open or short in VSV circuit for vapor pressure sensor
VSV for vapor pressure sensor
Charcoal canister cracked, hole or damaged
Fuel tank over fill check valve cracked or damaged
ECM
P0450
(DI±103)Evaporative Emission Control
System Pressure Sensor Mal-
function
Open or short in vapor pressure sensor circuit
V
P0451
(DI±103)Evaporative Emission Control
System Pressure Sensor Range/
PerformanceVapor pressure sensor
ECM
P0500
(DI±105)Vehicle Speed Sensor Malfunc-
tion
Combination meter
Open or short in vehicle speed sensor circuit
Vehicle speed sensor
ECM

P0505
(DI±107)Idle Control System MalfunctionErectric throttle control system
Air induction system
*1: 


MIL lights up

± DIAGNOSTICSENGINE
DI±17
2001 PRIUS (RM778U)
MANUFACTURER CONTROLLED:
DTC No.
(See Page)Detection ItemTrouble AreaMIL*1Memory
P1125
(DI±108)Throttle Control Motor Circuit
MalfunctionOpen or short in throttle control motor circuit
Throttle control motor
ECM

P1127
(DI±110)ETCS Actuator Power Source
Circuit MalfunctionOpen in ETCS power source circuit
ECM
P1128
(DI±112)Throttle Control Motor Lock Mal-
functionThrottle control motor
Throttle body
P1129
(DI±114)Electric Throttle Control System
MalfunctionElectric throttle control system
ECM
P1300
(DI±115)Igniter Circuit Malfunction (No.1)
Ignition system
Open or short in IGF1 and IGT1 circuit from No.1 ignition coil
with igniter to ECM
No.1 ignition coil with igniter
ECM

P1305
(DI±115)Igniter Circuit Malfunction (No.2)
Ignition system
Open or short in IGF2 and IGT2 circuit from No.2 ignition coil
with igniter to ECM
No.2 ignition coil with igniter
ECM

P1310
(DI±115)Igniter Circuit Malfunction (No.3)
Ignition system
Open or short in IGF2 and IGT3 circuit from No.3 ignition coil
with igniter to ECM
No.3 ignition coil with igniter
ECM

P1315
(DI±115)Igniter Circuit Malfunction (No.4)
Ignition system
Open or short in IGF1 and IGT4 circuit from No.4 ignition coil
with igniter to ECM
No.4 ignition coil with igniter
ECM

P1346
(DI±120)VVT Sensor/Camshaft Position
Sensor Circuit Range/Perfor-
mance Problem (Bank 1)Mechanical system (Jumping teeth of timing belt, belt
stretched)
ECM

P1349
(DI±121)VVT System Malfunction (Bank
1)
Valve timing
OCV
VVT controller assembly
ECM

P1430
(DI±127)Vacuum Sensor for Adsorber
and Catalyst System Circuit Mal-
functionOpen or short circuit in vacuum sensor circuit
Vacuum sensor for HC adsorber and catalyst system
ECM

P1431
(DI±131)Vacuum Sensor for Adsorber
and Catalyst System CIrcuit
Rangel Performance ProblemVacuum sensor for HC adsorber and catalyst system
Vacuum line
P1436
(DI±133)Variable Value Malfunction
Vacuum line
Actuator for HC adsorber and catalyst system
Front exhaust pipe

P1437
(DI±135)Vacuum Line Malfunction
Vacuum line
VSV for HC adsorber and catalyst system
Check valve


A14050
G±R
(Shielded)
512
IA2
1A
3
2
1
1EFI
3
B±G
F13B
MAIN
FL Block No. 1
BatteryEngine Room J/B
BR 1F
1K 1
2 3
11BW±B4
EB A
J7
J/C 1 2M1 Mass
Air Flow
Meter
A A 3
BE9
E810
VG
EVGECM
EFI
Relay
IEMREL
E8 G±R
19 G
R
F18 FL Block No. 2
F12W±B
J1
J/CJ9
J/C A
AW±B25
DI±24
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
Read freeze frame data using TOYOTA hand±held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected, when troubleshooting it is useful for determining
whether the vehicle was running or stopped, the engine warmed up or not, the air±fuel ratio lean or rich, etc.
at the time of the malfunction.
1 Connect OBD II scan tool or TOYOTA hand±held tester, and read value of mass
air flow rate.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(b) Turn ignition switch ON and push the OBD II scan tool or TOYOTA hand±held tester main switch ON.
(c) Start the engine.
CHECK:
Read mass air flow rate on the OBD II scan tool or TOYOTA hand±held tester.
RESULT:
Type IType II
Mass air flow rate (gm/sec.)0.0271.0 or more

BE6653A01589
A01588
ON
3 (+)
A13618
VG (+)
START
± DIAGNOSTICSENGINE
DI±25
2001 PRIUS (RM778U)
Type I Go to step 2.
Type II Go to step 5.
2 Check voltage of mass air flow meter power source.
PREPARATION:
(a) Disconnect the mass air flow meter connector.
(b) Turn ignition switch ON.
CHECK:
Measure voltage between terminal 4 of mass air flow meter con-
nector and body ground.
OK:
Voltage: 9 ± 14 V
NG Check for open in harness and connector
between EFI main relay (Marking: EFI) and
mass air flow meter (See page IN±41).
OK
3 Check voltage between terminal VG of ECM connector and body ground.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Start the engine.
CHECK:
Measure voltage between terminal VG of ECM and body
ground while engine is idling.
OK:
Voltage:
1.1 ± 1.5 V (P position and A/C switch OFF)
OK Check and replace ECM (See page IN±41).
NG

A13619
EVG
DI±26
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
4 Check for open and short in harness and connector between mass air flow meter
and ECM (See page IN±41).
NG Repair or replace harness or connector.
OK
Replace mass air flow meter.
5 Check continuity between terminal EVG of ECM connector and body ground.
PREPARATION:
Remove the ECM with connector still connected (See page
SF±62).
CHECK:
Check continuity between terminal EVG of ECM connector and
body ground.
OK:
Continuity (1 W or less)
NG Check and replace ECM (See page IN±41).
OK
6 Check for open in harness and connector between mass air flow meter and ECM
(See page IN±41).
NG Repair or replace harness or connector.
OK
Replace mass air flow meter.

A00310
E8
E822
18ECM
5V
THA
E2
E1 R
R±B
BR 4
5 (Built into mass air flow meter)M1
Intake Air Temp. Sensor
± DIAGNOSTICSENGINE
DI±29
2001 PRIUS (RM778U)
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

If DTC P0110 , P0115 and P0120 are output simultaneously, E2 (sensor ground) may be open.

Read freeze frame data using TOYOTA hand±held tester or OBD II scan tool. Because freeze frame
records the engine conditions when the malfunction is detected, when troubleshooting it is useful for
determining whether the vehicle was running or stopped, the engine warmed up or not, the air±fuel
ratio lean or rich, etc. at the time of the malfunction.
1 Connect OBD II scan tool or TOYOTA hand±held tester, and read value of intake
air temperature.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to DLC3.
(b) Turn the ignition switch ON and push the OBD II scan tool or TOYOTA hand±held tester main switch
ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA hand±held tester.
OK:
Same as actual air intake temperature.
HINT:

If there is open circuit, OBD II scan tool or TOYOTA hand±held tester indicates ± 40°C (± 40°F).

If there is short circuit, OBD II scan tool or TOYOTA hand-held tester indicates 140°C (284°F) or more.
NG ±40°C (±40°F) ....Go to step 2.
140°C (284°F) or more ....Go to step 4.
OK
Check for intermittent problems
(See page DI±3).