DI±4
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
The diagnosis system operates in normal mode
during normal vehicle use. It also has a check mode
for technicians to simulate malfunction symptoms
and troubleshoot. Most DTCs use 2 trip detection
logic* to prevent erroneous detection, and ensure
thorough malfunction detection. By switching the
ECM to check mode when troubleshooting, the
technician can cause the MIL to light up for a mal-
function that is only detected once or momentarily
(TOYOTA hand±held tester only). (See step 2)
*2 trip detection logic:
When a malfunction is first detected, the malfunc-
tion is temporarily stored in the ECM memory (1st
trip).
If the same malfunction is first detected again during the second
drive test, this second detection causes the MIL to light up (2nd
trip). (However, the IG switch must be turned OFF between the
1st trip and the 2nd trip.)
Freeze frame data:
Freeze frame data records the engine condition
when a misfire (DTC P0300 ± P0304) or fuel trim
malfunction (DTC P0171, P0172) or other malfunc-
tion (first malfunction only), is detected.
Because freeze frame data records the engine
conditions (fuel system, calculated load, engine
coolant temperature, fuel trim,engine speed, ve-
hicle speed, etc.) when the malfunction is detected,
when troubleshooting it is useful for determining
whether the vehicle was running or stopped, the en-
gine warmed up or not, the air±fuel ratio lean or rich,
etc. at the time of the malfunction.
Priorities for troubleshooting:
If troubleshooting priorities for multiple DTCs are given in the
applicable DTC chart, these should be followed.
If no instructions are given troubleshoot DTCs according to the
following priorities.
(1) DTCs other than fuel trim malfunction (DTC P0171,
P0172), and misfire (DTC P0300 ± P0304).
(2) Fuel trim malfunction (DTC P0171, P0172).
(3) Misfire (DTC P0300 ± P0304).
N09214
FI2547
± DIAGNOSTICSENGINE
DI±5
2001 PRIUS (RM778U)
(b) Check the DLC3.
The vehicle's ECM uses ISO 9141±2 for communication.
The terminal arrangement of DLC3 complies with SAE
J1962 and matches the ISO 9141±2 format.
Terminal No.Connection / Voltage or ResistanceCondition
7Bus Line / Pulse generationDuring transmission
4Chassis Ground / e Body Ground 1 W or lessAlways
5Signal Ground / e Body Ground 1 W or lessAlways
16Battery Positive / e Body Ground 9 ± 14 VAlways
HINT:
If your display shows ºUNABLE TO CONNECT TO VEHICLEº
when you have connected the cable of the TOYOTA hand±held
tester or OBDII scan tool to DLC3, turned the ignition switch ON
and operated the scan tool, there is a problem on the vehicle
side or tool side.
If communication is normal when the tool is connected to
another vehicle, inspect DLC3 on the original vehicle.
If communication is still not possible when the tool is con-
nected to another vehicle, the problem is probably in the
tool itself, so consult the Service Department listed in the
tool's instruction manual.
2. INSPECT DIAGNOSIS (Normal Mode)
(a) Check the MIL
(1) The MIL comes on when the ignition switch is turned
ON and the engine is not running.
HINT:
If the MIL does not light up, troubleshoot the combination meter
(See page BE±42).
(2) When the engine started, the MIL should go off. If
the lamp remains on, the diagnosis system has de-
tected a malfunction or abnormality in the system.
(b) Check the DTC.
NOTICE:
If there is no DTC in the normal mode, check the 1st
trip DTC using Continuous Test Result function
(Mode 7 for SAE J1979) or the TOYOTA hand±held
tester or OBDII scan tool.
DI±6
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
TOYOTA hand±held tester only:
When the diagnosis system is switched from normal
mode to check mode, it erases all DTCs and freezed
frame data recorded in normal mode. So before
switching modes, always check the DTCs and
freezed frame data, and note them down.
(1) Prepare the TOYOTA hand±held tester or OBDII
scan tool (complying with SAE J1978).
(2) Connect the TOYOTA hand±held tester or OBDII
scan tool to DLC3 under the instrument panel lower
pad.
(3) Turn the ignition switch ON and turn the TOYOTA
hand±held tester or OBDII scan tool switch ON.
(4) Use the TOYOTA hand±held tester or OBDII scan
tool to check the DTCs and freezed frame data;
note them down. (For operating instructions, see
the OBDII scan tool's instruction book.)
(5) See step 4 to confirm the details of the DTCs.
NOTICE:
When simulating symptoms with an OBDII scan tool
(excluding TOYOTA hand±held tester) to check the
DTCs, use normal mode. For code on the DTC chart
subject to º2 trip detection logicº, perform the follow-
ing either action.
Turn the ignition switch OFF after the symptom is
simulated the first time. Then repeat the simulation
process again. When the problem has been simulated
twice, the MIL lights up and the DTCs are recorded in
the ECM.
Check the 1st trip DTC using Mode 7 (Continuous Test
Results) for SAE J1979.
(c) Clear the DTC.
The DTCs and freezed frame data will be erased by either
action.
(1) Operating the TOYOTA hand±held tester or OBDII
scan tool (complying with SAE J1978) to erase the
codes. (See the OBDII scan tool's instruction book
for operating instructions.)
(2) Disconnecting the battery terminals or EFI fuse.
NOTICE:
If the TOYOTA hand±held tester switches the ECM from the
normal mode to the check mode or vice±versa, or if the
ignition switch is turned from ON to ACC or OFF during
check mode, the DTCs and freezed frame data will be
erased.
A04438A13924A14466
TC
CG
A14060
DI±10
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
5 Check ignition timing.
PREPARATION:
(a) Warm up engine to normal operating temperature.
(b) Shift transmission into P position.
(c) Keep the engine speed at idle.
(d) Using SST, connect terminals TE1 and E1 of DLC1.
SST 09843±18020
(e) Using a timing light, connect the tester to the ignition coil
connector wire (See page EM±11).
(f) Transit to inspection mode.
CHECK:
Check ignition timing.
OK:
Ignition timing: 7 ± 15° BTDC at idle
NG Proceed to page IG±1 and continue to trouble-
shoot.
OK
Proceed to problem symptoms table on page
DI±22.
6 Check fuel pressure.
PREPARATION:
(a) Be sure that enough fuel is in the tank.
(b) Connect the TOYOTA hand±held tester to the DLC3.
(c) Turn the ignition switch ON and push the TOYOTA hand±
held tester main switch ON.
(d) Use the ACTIVE TEST mode to operate the fuel pump.
(e) Please refer to the TOYOTA hand±held tester operator's
manual for further details.
(f) If you have no TOYOTA hand±held tester, connect the
positive (+) and negative (±) leads from the battery to the
fuel pump connector (See page SF±6).
CHECK:
Check for fuel pressure in the fuel inlet hose when it is pinched
off.
HINT:
At this time, you will hear a fuel flowing noise.
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
DI±18
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)P1455
(DI±140)
Vapor Reducing Fuel Tank Sys-
tem Leak Detected (Small Leak)
Hose and pipe
Heated oxygen sensor
Fuel system
VVT system
Ignition system
Mass air flow meter
ECM
P1525
(DI±141)Resolver Circuit
MalfunctionHV ECU
Engine ECU±
P1600
(DI±143)ECM BATT MalfunctionOpen in back up power source circuit
ECM
P1633
(DI±145)ECU Malfunction (ETCS Circuit)ECM
P1636
(DI±146)HV ECU MalfunctionHV ECU
Engine ECU
P1637
(DI±148)EGSTP Signal MalfunctionHV ECU
Engine ECU±
P1656
(DI±150)OCV Circuit Malfunction (for
VVT±i)Open or short in OCV circuit
OCV
ECM
P3190
(DI±153)Poor Engine Power
Air induction system
Throttle body
Fuel pressure
Engine
Mass air flow meter
P3191
(DI±153)Engine dose not start
Mass air flow meter
Out of fuel
Engine coolant temp. sensor
Crankshaft position sensor
Camshaft position sensor
ECM
*1: MIL lights up
FI7130A14461
Vehicle
speed
Constant
speed
Start
online(c)(d)
IG SW
OFF30 sec. 36 sec.Time
(a) (b)
DI±50
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DTC P0130 Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 1)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI±44.
DTC No.DTC Detecting ConditionTrouble Area
P0130
Voltage output of oxygen sensor remains at 0.42 V or more, or
0.48 V or less, during idling after the engine is warmed up (2
trip detection logic)
Open or short in heated oxygen sensor circuit
Heated oxygen sensor
Air induction system
Fuel pressure
Injector
ECM
HINT:
Sensor 1 refers to the sensor closer to the engine body.
The oxygen sensor's output voltage and the short-term fuel trim value can be read using the OBD II scan
tool or TOYOTA hand-held tester.
WIRING DIAGRAM
Refer to DTC P0125 on page DI±44.
CONFIRMATION DRIVING PATTERN
(a) Connect the TOYOTA hand±held tester to the DLC3.
(b) Switch the TOYOTA hand±held tester from normal mode to check mode (See page DI±3).
(c) Start the engine and pass for 30 sec. or more.
(d) Drive the vehicle at constant speed for 36 sec. or more.
HINT:
If a malfunction exists, the MIL will light up during step (d).
NOTICE:
If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
If you do not have a TOYOTA hand±held tester, turn the ignition switch OFF after performing steps
(c) to (d), then perform steps (c) to (d) again.
DI6V3±02