TOYOTA CAMRY 1999 Service Repair Manual

P24296
ECM
Throttle Position
Sensor
VC
VTA1
E2
S05019
ECM
1
3
25 V
VC
VTA1
E2 Y
L
BR Throttle Position Sensor
E102
23
18 E10
E10
± DIAGNOSTICSENGINE (1MZ±FE)
DI±239
474 Author: Date:
DTC P0120 Throttle/Pedal Position Sensor/Switch ºAº
Circuit Malfunction
CIRCUIT DESCRIPTION
The throttle position sensor is mounted in the throttle body and
detects the throttle valve opening angle. When the throttle valve
is fully closed, a voltage of approximately 0.7 V is applied to ter-
minal VTA of the ECM. The voltage applied to the terminals VTA
of the ECM increases in proportion to the opening angle of the
throttle valve and becomes approximately 2.7 ~ 5.2 V when the
throttle valve is fully opened. the ECM judges the vehicle driving
conditions from these signals input from terminals VTA and
uses them as one of the conditions for deciding the air±fuel ratio
correction, power increase correction and fuel±cut control etc.
DTC No.DTC Detecting ConditionTrouble Area
P0120
Condition (a) or (b) continues:
(a) VTA
0.1 V
(b) VTA
4.9 V

Open or short in throttle position sensor circuit

Throttle position sensor

ECM
HINT:
After confirming DTC P0120, use the OBD II scan tool or TOYOTA hand±held tester to confirm the throttle
valve opening percentage and closed throttle position switch condition.
Throttle valve opening position
expressed as percentage
Trouble Area
Throttle valve fully closedThrottle valve fully open
Trouble Area
0 %0 %VC line open
VTA line open or short
Approx. 100 %Approx. 100 %E2 line open
WIRING DIAGRAM
DI07K±06

FI7052
DI±240
± DIAGNOSTICSENGINE (1MZ±FE)
475 Author: Date:
INSPECTION PROCEDURE
HINT:

If DTCs P0110(Intake Air temp. Circuit Malfunction), P0115(Engine Coolant Temp. Circuit Malfunc-
tion), P0120(Throttle/Pedal Position Sensor/Switch ºAº Circuit Malfunction) and P1410 are output si-
multaneously, 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 throttle valve
opening percentage.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tes-
ter 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 the throttle valve opening percentage.
OK:
Throttle valveThrottle valve opening position
expressed as percentage
Fully openApprox. 75 %
Fully closedApprox. 10 %
OK Check for intermittent problems
(See page DI±197).
NG

A00437
1 (+) ON
BE6653
S05338
S05339
1
2
3
± DIAGNOSTICSENGINE (1MZ±FE)
DI±241
476 Author: Date:
2 Check voltage between terminal 1 of wire harness side connector and body
ground.
PREPARATION:
(a) Disconnect the throttle position sensor connector.
(b) Turn the ignition switch ON.
CHECK:
Measure voltage between terminal 1 of wire harness side con-
nector and body ground.
OK:
Voltage: 4.5 ~ 5.5 V
NG Go to step 5.
OK
3 Check throttle position sensor.
PREPARATION:
Disconnect the throttle position sensor connector.
CHECK:
Measure voltage between terminals 1, 3 and 2 of throttle
position sensor.
OK:
TerminalsThrottle valveResistance
1 ~ 2'2.5 ~ 5.9 kW
3 ~ 2Fully closed0.2 ~ 6.3 kW
3 ~ 2Fully open2.0 ~ 10.2 kW
NG Replace throttle position sensor.
OK

A02021
ON
VTA1 (+) E2 (±)
A02022
ON
VC (+) E2 (±)
DI±242
± DIAGNOSTICSENGINE (1MZ±FE)
477 Author: Date:
4 Check voltage between terminals VTA1 and E2 of ECM.
PREPARATION:
(a) Remove the glove compartment (See page SF±73).
(b) Turn the ignition switch ON.
CHECK:
Measure voltage between terminals VTA1 and E2 of the ECM
connector.
OK:
Throttle valveVoltage
Fully closed0.3 ~ 1.0 V
Fully open2.7 ~ 5.2 V
NG Check for open and short in harness and
connector between ECM and throttle position
sensor (VTA line) (See page IN±31).
OK
Check and replace ECM (See page IN±31).
5 Check voltage between terminals VC and E2 of ECM.
PREPARATION:
(a) Remove the glove compartment (See page SF±73).
(b) Turn the ignition switch ON.
CHECK:
Measure voltage between terminals VC and E2 of the ECM
connector.
OK:
Voltage: 4.5 ~ 5.5 V
NG Check and replace ECM (See page IN±31).
OK
Check for open in harness and connector
between ECM and sensor (VC line)
(See page IN±31).

± DIAGNOSTICSENGINE (1MZ±FE)
DI±243
478 Author: Date:
DTC P0121 Throttle/Pedal Position Sensor/Switch ºAº
Circuit Range/Performance Problem
CIRCUIT DESCRIPTION
Refer to DTC P0120 (Throttle/Pedal Position Sensor/Switch "A" Circuit Malfunction) on page DI±239.
DTC No.DTC Detecting ConditionTrouble Area
P0121
After vehicle speed has been exceeded 30 km/h (19 mph)
even once, output value of throttle position sensor is out of
applicable range while vehicle speed between 30 km/h (19
mph) and 0 km/h (0 mph)
(2 trip detection logic)

Throttle position sensor
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 P0121) being output?
YES Go to relevant DTC chart.
NO
Replace throttle position sensor.
DI07L±06

P21242 FI7210
A00027
Atmosphere
CoverIdeal Air±Fuel Mixture
Air Fuel Ratio
RicherLeaner
Exhaust GasFlange
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platium Electrode
Heater
Coating(Ceramic)
Output Voltage
DI±244
± DIAGNOSTICSENGINE (1MZ±FE)
479 Author: Date:
DTC P0125 Insufficient Coolant Temp. for Closed Loop
Fuel Control (Except 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 oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the
stoichiometric air±fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust
gas and provide feedback to the computer for control of the air±fuel ratio.
When the air±fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen
sensor informs the ECM of the LEAN condition (small electromotive force: < 0.45 V).
When the air±fuel ratio is RICHER than the stoichiometric air±fuel ratio the oxygen concentration in the ex-
haust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive
force: > 0.45 V). The ECM judges by the electromotive force from the oxygen sensor whether the air±fuel
ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sen-
sor causes output of abnormal electromotive force, the ECM is unable to perform accurate air±fuel ratio con-
trol.
The heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled by
the ECM. When the intake air volume is low (the temperature of the exhaust gas is low) current flows to the
heater to heat the sensor for accurate oxygen concentration detection.
DTC No.DTC Detecting ConditionTrouble Area
P0125
After engine is warmed up, heated oxygen sensor (bank 1, 2
sensor 1) output does not indicate RICH ( 0.45 V ) even
once when conditions (a), (b), (c) and (d) continue for at least
2 min.:
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40
SPD and 100 km/h (25
SPD and
62 mph)
(c) Throttle valve does not fully closed
(d) 140 sec. or more after starting engine
Fuel system

Injector

Ignition system

Gas leakage on exhaust system

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

Heated oxygen sensors (bank 1, 2 sensor 1)

ECM
DI07M±08

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.

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

± 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

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.