O2 sensor TOYOTA PRIUS 2001 Service Repair Manual

A09300
Vehicle speed
40 km/h
(25 mph)
Idling(c)(d)
(e)
(a)
IG SW OFF
(b)
(e)
60 sec.
or more(d)
(d) Once
40 sec.
or moreTwice
40 sec.
or more11 times
40 sec.
or more
10 sec. 10 sec.(e)
10 sec.
± DIAGNOSTICSENGINE
DI±59
2001 PRIUS (RM778U)
DTC P0136 Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI±44.
DTC No.DTC Detecting ConditionTrouble Area
P0136
Voltage output of the heated oxygen sensor remains at 0.45 V
or more, or 0.55 V or less when the vehicle is driven at 40 km/h
(25 mph) or more after the engine is warmed up.
(2 trip detection logic).

Open or short in heated oxygen sensor circuit

Heated oxygen sensor
HINT:
Sensor 2 refers to the sensor farther away from the engine body.
WIRING DIAGRAM
Refer to DTC P0125 on page DI±44.
CONFIRMATION DRIVING PATTERN
(a) Connect the hand±held tester to the DLC3.
(b) Switch the hand±held tester from the Normal Mode to the Check (Test) Mode (See page DI±3).
(c) Start the engine and let the engine idle for 60 seconds or more.
(d) Drive the vehicle at 40 km/h (25 mph) or more for 40 seconds or more.
(e) Let the engine idle for 10 seconds or more.
(f) Preform steps (d) to (e) 11 times.
HINT:

During performing the steps (d) to (e) 11 times, drive the vehicle at over 65 km and make the fuel cut
happen for over 3 sec.

If a malfunction exists, the MIL will be indicated on the multi information display during step (f).
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 hand±held tester, turn the ignition switch OFF after performing steps (c) to (f),
then perform steps (c) to (f) again.
DI6V6±02

DI±60
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
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 Are there any other codes (besides DTC P0136) being output?
YES Go to relevant DTC chart.
NO
2 Check for open and short in harness and connector between ECM and oxygen
sensor (See page IN±41).
NG Repair or replace harness or connector.
OK
3 Check output voltage of oxygen sensor.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(b) Warm up the engine to normal operating temp.
CHECK:
Read voltage output of oxygen sensor when engine suddenly raced.
HINT:
Perform a quick racing of 2,000 rpm or more 3 times by using the accelerator pedal.
OK:
Oxygen sensor output voltage: Alternates from 0.40 V or less to 0.50 V or more.
OK Check that each connector is properly con-
nected.
NG
Replace oxygen sensor.

± DIAGNOSTICSENGINE
DI±61
2001 PRIUS (RM778U)
DTC P0171 System too Lean (Fuel Trim)
DTC P0172 System too Rich (Fuel Trim)
CIRCUIT DESCRIPTION
Fuel trim refers to the feedback compensation value compared against the basic injection time. Fuel trim
includes short±term fuel trim and long±term fuel trim.
Short±term fuel trim is the short±term fuel compensation used to maintain the air±fuel ratio at its ideal
theoretical value. The signal from the oxygen sensor indicates whether the air±fuel ratio is RICH or LEAN
compared to the ideal theoretical value, triggering a reduction in fuel volume if the air±fuel ratio is rich, and
an increase in fuel volume if it is lean.
Long±term fuel trim is overall fuel compensation carried out long±term to compensate for continual deviation
of the short±term fuel trim from the central value due to individual engine differences, wear over time and
changes in the usage environment.
If both the short±term fuel trim and long±term fuel trim are LEAN or RICH beyond a certain value, it is
detected as a malfunction and the MIL lights up.
DTC No.DTC Detecting ConditionTrouble Area
P0171
When the air±fuel ratio feedback is stable after engine warming
up, the fuel trim is considerably in error on the RICH side
(2 trip detection logic)

Air induction system

Injector blockage

Mass air flow meter

Engine coolant temp. sensor

Fuel pressure

Gas leakage on exhaust system

Open or short in heated oxygen sensor (bank 1 sensor 1)
circuit

Heated oxygen sensor (bank 1 sensor 1)
P0172
When air fuel ratio feedback is stable after warming up engine,
the fuel trim is considerably in error on LEAN side (2 trip detec-
tion logic)

Injector leak, blockage

Mass air flow meter

Engine coolant temp. sensor

Ignition system

Fuel pressure

Gas leakage on exhaust system

Open or short in heated oxygen sensor (bank 1, 2 sensor 1)
circuit

Heated oxygen sensor (bank 1, 2 sensor 1)

ECM
HINT:

When DTC P0171 is recorded, the actual air±fuel ratio is on the LEAN side. When DTC P0172 is re-
corded, the actual air±fuel ratio is on the RICH side.

If the vehicle runs out of fuel, the air±fuel ratio is LEAN and DTC P0171 is recorded. The MIL then
comes on.

If the total of the short±term fuel trim value and long±term fuel trim value is within + 38 %, the system
is functioning normally.

The oxygen sensor output voltage and the short±term fuel trim value can be read using the OBD II scan
tool or TOYOTA hand±held tester.
DI6V7±02

DI±62
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
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 Check air induction system (See page SF±1).
NG Repair or replace.
OK
2 Check injector injection (See page SF±12).
NG Replace injector.
OK
3 Check mass air flow meter and engine coolant temp. sensor
(See page SF±22 and SF±49).
NG Repair or replace.
OK
4 Check for spark and ignition (See page IG±1).
NG Repair or replace.
OK

P18349
± DIAGNOSTICSENGINE
DI±63
2001 PRIUS (RM778U)
5 Check fuel pressure (See page SF±6).
NG Check and repair fuel pump and fuel pipe line.
OK
6 Check gas leakade on exhaust system.
NG Repair or replace.
OK
7 Check the output voltage of heated oxygen sensor during idling.
PREPARATION:
Warm up the oxygen sensor the engine at 2,500 rpm for approx. 90 sec.
CHECK:
Use the OBD II scan tool or TOYOTA hand±held tester read the output voltage of the heated oxygen sensor
during idling.
OK:
Oxygen sensor output voltage:
Alternates repeatedly between less than 0.4 V and more than 0.55 V (See the following table).
OK Go to step 9.
NG

DI±64
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
8 Check for open and short in harness and connector between ECM and heated
oxygen sensor (See page IN±30).
NG Repair or replace harness or connector.
OK
Replace heated oxygen sensor.
9 Perform confirmation driving pattern (See page DI±50).
GO
10 Is there DTC P0171 being output again?
YES Check and replace ECM.
NO
11 Did vehicle runs out of fuel in the past?
NO Check for intermittent problems.
YES
DTC P0171 or P0172 is caused by running out
of fuel.

± DIAGNOSTICSENGINE
DI±65
2001 PRIUS (RM778U)
DTC P0300 Random/Multiple Cylinder Misfire Detected
DTC P0301 Cylinder 1 Misfire Detected
DTC P0302 Cylinder 2 Misfire Detected
DTC P0303 Cylinder 3 Misfire Detected
DTC P0304 Cylinder 4 Misfire Detected
CIRCUIT DESCRIPTION
Misfire: The ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in
the crankshaft rotation for each cylinder.
The ECM counts the number of times the engine speed change rate indicates that misfire has occurred. And
when the misfire rate equals or exceeds the count indicating that the engine condition has deteriorated, the
MIL lights up.
If the misfire rate is high enough and the driving conditions will cause catalyst overheating, the MIL blinks
when misfiring occurs.
DTC No.DTC Detecting ConditionTrouble Area
P0300Mi fi i f d li d i d t t d d i ti l

Open or short in engine wire

Connector connection

Vacuum hose connection

I
gnition systemP0300
P0301
P0302
P0303
P0304
Misfiring of random cylinders is detected during any particular
200 or 1,000 revolutions
For any particular 200 revolutions for the engine, misfiring is
detected which can cause catalyst overheating
(This causes MIL to blink)

Ignition system

Injector

Fuel pressure

Manifold absolute pressure sensor

En
gine coolant temp. sensorP0304(This causes MIL to blink)
Engine coolant tem. sensor

Compression pressure

Valve clearance

Valve timing

ECM
HINT:

When the 2 or more codes for a misfiring cylinder are recorded repeatedly but no random misfire code
is recorded, it indicates that the misfires were detected and recorded at different times.

There is a case where the cylinder other than memorized has an accidental fire (the cylinder which is
one ahead of fired cylinder), so. at the time of checking all the checking items and if there is no ab-
normality, check the cylinder which is different from the recorded cylinder as fired.
DI6V8±03

± DIAGNOSTICSENGINE
DI±69
2001 PRIUS (RM778U)
OK Go to step 5.
NG
4 Check resistance of injector of misfiring cylinder (See page SF±9).
NG Replace injector.
OK
Check for open and short in harness and
connector between injector and ECM
(See page IN±41).
5 Check fuel pressure (See page SF±6).
NG Check and repair fuel pump and fuel pipe line
(See page SF±1).
OK
6 Check injector injection (See page SF±12).
NG Replace injector.
OK
7 Check mass air flow merer and engine coolant temp. sensor
(See page SF±22 and SF±49).
NG Repair or replace.

A14027
Knock
SensorECM
KNK1 E7 1
EA1128
B
BR
EB
BR(Shielded)
A
J8 A
J9J/C
± DIAGNOSTICSENGINE
DI±71
2001 PRIUS (RM778U)
DTC P0325 Knock Sensor 1 Circuit Malfunction
CIRCUIT DESCRIPTION
The knock sensor is fitted to the cylinder block to detect engine knocking. This sensor contains a piezoelec-
tric element which generates a voltage when it becomes deformed, which occurs when the cylinder block
vibrates due to knocking. If engine knocking occurs, ignition timing is retarded to suppress it.
DTC No.DTC Detecting ConditionTrouble Area
P0325No knock sensor 1 signal to ECM with engine speed, 2,000
rpm or more
Open or short in knock sensor 1 circuit

Knock sensor 1 (looseness)

ECM
HINT:
If the ECM detects above diagnosis conditions, it operates the fail safe function in which the corrective retard
angle value is set to the maximum value.
WIRING DIAGRAM
DI6V9±02

A13628
E7 Connector LOCK
KNK1
DI±72
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
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 Check continuity between terminal KNK1 of ECM connector and body ground.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Disconnect the E7 connector of the ECM.
CHECK:
Measure resistance between terminal KNK1 of the ECM con-
nector and body ground.
OK:
Resistance: 1 MW or higher
OK Go to step 3.
NG
2 Check knock sensor (See page SF±56).
NG Replace knock sensor.
OK
3 Check for open and short in harness and connector between ECM and knock
sensor (See page IN±41).
NG Repair or replace harness or connector.
OK