Page 2665 of 4770

A07444
BatteryJunction Connector
MREL
ECM
B
B+
E1
E03
E03
E1E1
E03 OXL1
HTL1
OXR1
HTR
OXS
HTS
E8E8 E10 E11E7
E10
E10
E108
12
4
11
30
3
8
9
Y±R
3
2
4
1
W
BR
L±B
B
BR
3 2
4
1
B±Y
B±Y
B±Y
A A B Junction Connector
B
J28 J27
J27 B±YJunction Connector
2K
2J
3
1
2
5
EFI
2C 2A 1 5
F6
F4 1
1
B
W±B
EB
FL
MAINFusible
Link
Block
E03
Engine
Room
J/B
B±G
Heated Oxygen
Sensor
(Bank 1 Sensor 2)3
2
1
EDEC
P±BA
A
BR
BR4 B±YHeated Oxygen
Sensor
(Bank 1 Sensor 1)II3 B±WAC
J36 J35B±W
EFI Relay
BR
BR
2 7B±Y9
Heated Oxygen
Sensor
(Bank 2 Sensor 1)
D
± DIAGNOSTICSENGINE (1MZ±FE)
DI±245
480 Author: Date:
HINT:
After confirming DTC P0125, use the OBD II scan tool or TOYOTA hand-held tester to confirm voltage output
of the heated oxygen sensors (bank 1, 2 sensor 1) from CURRENT DATA.
If voltage output of the heated oxygen sensors (bank 1, 2 sensor 1) is less than 0.1 V, heated oxygen sensors
(bank 1, 2 sensor 1) circuit may be open or short.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
If the vehicle run out fuel, the air±fuel ratio is LEAN and DTC P0125 will be recorded.
The MIL then comes on.
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.
Page 2666 of 4770
DI±246
± DIAGNOSTICSENGINE (1MZ±FE)
481 Author: Date:
1 Are there any other codes (besides DTC P0125) being output ?
YES Go to relevant DTC chart.
NO
2 Connect OBD II scan tool or TOYOTA hand±held tester, and read value for
voltage output of heated oxygen sensors (bank 1, 2 sensor 1).
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.(above 75°C (169°F)).
CHECK:
Read voltage output of the heated oxygen sensors (bank 1,2 sensor 1) when engine is suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 times using accelerator pedal.
OK:
Heated oxygen sensors (bank 1, 2 sensor 1) output a RICH signal
(0.45 V or more) at least once.
OK Go to step 10.
NG
3 Check for open and short in harness and connector between ECM and heated
oxygen sensors (bank 1, 2 sensor 1) (See page IN±31).
NG Repair or replace harness or connector.
OK
Page 2667 of 4770
± DIAGNOSTICSENGINE (1MZ±FE)
DI±247
482 Author: Date:
4 Check whether misfire is occurred or not by monitoring DTC and data list.
NG Perform troubleshooting for misfire
(See page DI±351).
OK
5 Check air induction system (See page SF±1).
NG Repair or replace.
OK
6 Check EGR system (See page EC±11).
NG Replace EGR system.
OK
7 Check fuel pressure (See page SF±6).
NG Check and repair fuel pump, fuel pipe line and
filter (See page SF±1).
OK
8 Check injector injection (See page SF±25)
NG Replace injector.
OK
Page 2668 of 4770
DI±248
± DIAGNOSTICSENGINE (1MZ±FE)
483 Author: Date:
9 Check gas leakage on exhaust system.
NG Repair or replace.
OK
Replace heated oxygen sensors
(bank 1, 2 sensor 1).
10 Perform confirmation driving pattern (See page DI±255).
Go
11 Is there DTC P0125 being output again ?
YES Check and replace ECM
(See page IN±31).
NO
12 Did vehicle runs out of fuel in the past ?
NO Check for intermittent problems
(See page DI±197).
NO
DTC P0125 is caused by running out of fuel.
Page 2669 of 4770

A00477
CoverAtmosphere
Platinum
Electrode
Solid Electrolyte
(Zirconia Element)
Platinum
Electrode
Heater
Coating (Ceramic)
Exhaust Gas
(V)
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
17
Air±Fuel Ratio
2.4
16 15 12 1413 1918ECM Monitored
A/F Sensor Voltage
± DIAGNOSTICSENGINE (1MZ±FE)
DI±249
484 Author: Date:
DTC P0125 Insufficient Coolant Temp. for Closed Loop
Fuel Control (Only for California Spec.)
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three±way
catalytic converter is used, but for the most efficient use of the three±way catalytic converter, the air±fuel
ratio must be precisely controlled so that it is always close to the stoichiometric air±fuel ratio.
The A/F sensor has the characteristic that provides output voltage
* approximately proportional to the existing
air±fuel ratio. The A/F sensor output voltage
* is used to provide feedback for the ECM to control the air±fuel
ratio.
By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air±fuel ratio
and control the proper injection time immediately. If the A/F sensor is malfunctioning, ECM is unable to per-
form accurate air±fuel ratio control.
The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the
ECM. When the intake air volume is low (the temp. of the exhaust gas is low), current flows to the heater
to heat the sensor for accurate oxygen concentration detection.
*: The voltage value changes at the inside of the ECM only.
DTC No.DTC Detecting ConditionTrouble Area
P0125
After engine is warmed up, A/F sensor output* does not
change when conditions (a), (b) and (c) continue for at least
1.5 min.
*: Output value changes at inside of ECM only.
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40 ~ 100 km/h (25 ~ 62 mph)
(c) Throttle valve does not fully closed
(d) After starting engine 140 secFuel system
Injector
Ignition system
Gas leakage on exhaust system
Open or short in A/F sensor circuit (bank 1, 2 sensor 1)
A/F sensors (bank 1, 2 sensor 1)
ECM
DI07M±09
Page 2670 of 4770

A07445
B
BB B
2 142
31 23
4
BR
23
1
B±W P±BB B±WB±R
*
1L
E8 E8 E10 E10
E78 9 84 213 122011
AFR+
AFR±
AFL+
AFL± HAFR
OXS
HTS
MREL HAFLECM
3.3 V
3.3 V 3.0 V
3.0 V
E1
B+ E10 E10E10E10 1
J27
Engine Room J/B
F6
F4 2J
2A
2C2K
2
7
5 1
EFI Relay
1
1B
B±W
B±W
B EFI
1 2
2
52
22 3
L W±B1
1 2
A/F HTR
1
W
FL
MAIN FLEngine RoomBattery*
1B±W B
B
B±G
1
2 3
5
E04
E05
E03
*1B±R *1BR *G
*G
*B±W*L
ES1
J27 B
E
Junction
connector
A/F Sensor
(Bank 2, Sensor 1)
B±Y
A/F Sensor
(Bank 1, Sensor 2)
BRII1A
ABR
J22
Junction
Connector J24
Junction
Connector
B±Y
W±B
B±W
J35
J35J36A C
C
EB EC
A/F Sensor
(Bank 1, Sensor 1)
Engine Room
A/F HTR Relay
*: TMC Made
*: TMMK Made
Junction
Connector
4
to Analog±Digital
Converter
to Analog±Digital
Converter
DI±250
± DIAGNOSTICSENGINE (1MZ±FE)
485 Author: Date:
HINT:
After confirming DTC P0125, use the OBD II scan tool or TOYOTA hand-held tester to confirm voltage
output of heated oxygen sensors (bank 1, 2 sensor 1) from CURRENT DATA.
The ECM controls the voltage of AFR, AFL, AFR and AFL terminals of ECM to the fixed volt-
age. Therefore, it is impossible to confirm the A/F sensor output voltage without OBD II scan tool or
TOYOTA hand±held tester.
OBD II scan tool (excluding TOYOTA hand±held tester) displays the one fifth of the A/F sensor output
voltage which is displayed on the TOYOTA hand±held tester.
WIRING DIAGRAM
Page 2671 of 4770
± DIAGNOSTICSENGINE (1MZ±FE)
DI±251
486 Author: Date:
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 P0125) being output ?
YES Go to relevant DTC chart.
NO
Page 2672 of 4770

DI±252
± DIAGNOSTICSENGINE (1MZ±FE)
487 Author: Date:
2 Connect the OBD II scan tool or TOYOTA hand±held tester, and read value for
voltage output of A/F sensors (bank 1, 2 sensor 1).
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(b) Warm up the A/F sensors (bank 1, 2 sensor 1) with the engine at 2,500 rpm for approx. 90 sec.
CHECK:
Read voltage value of A/F sensors (bank 1, 2 sensor 1) on the screen of OBD II scan tool or TOYOTA hand±
held tester, when you perform all the following conditions.
HINT:
The voltage of AFR,AFL terminal of ECM is 3.3 fixed and the AFR,AFL terminal is 3.0 V fixed.
Therefore, it is impossible to check the A/F sensor output voltage at the terminals (AFR,AFL/
AFR,AFL) of ECM.
OK:
ConditionA/F Sensor Voltage value
Engine idlingN t i t 3 3 V (*0 660 V)E i idliNot remains at 3.3. V (*0.660 V)Engine idlingNot remains at 3.3. V ( 0.660 V)
Not remains at38V(
*0 76 V) or more
Driving at engine speed 1,500 rpm or more and vehicle
speed 40 km/h (25 mph) or move, and operate throttle valve
open and close
Not remains at 3.8 V (*0.76 V) or more
Not remains at 2.8 V (*0.56 V) or less
*: When you use the OBD II scan tool (excluding TOYOTA hand±held tester)
HINT:
During fuel enrichment, there is a case that the output voltage of A/F sensors (bank 1, 2 sensor 1) is
below 2.8 V (
* 0.56 V), it is normal.
During fuel cut, there is a case that the output voltage of A/F sensors (bank 1, 2 sensor 1) is above
3.8 V (
* 0.76 V), it is normal.
If output voltage of A/F sensors (bank 1, 2 sensor 1) remains at 3.30 V (* 0.660 V) even after performing
all the above conditions, A/F sensors (bank 1, 2 sensor 1) circuit may be open.
If output voltage of A/F sensor remains at 3.8 V (* 0.76 V) or more, or 2.8 V (* 0.56 V) or less even after
performing all the above conditions, A/F sensors (bank 1, 2 sensor 1) circuit may be short.
*: When you use the OBD II scan tool (excluding TOYOTA hand±held tester).
OK Go to step 10.
NG
3 Check for open and short in harness and connector between ECM and A/F
sensors (bank1, 2 sensor1) (See page IN±31).
NG Repair or replace harness or connector.
OK