TOYOTA CAMRY 1999 Service Repair Manual

P24296
Throttle Position
Sensor
VC
VTA
E2ECM
± DIAGNOSTICSENGINE (5S±FE)
DI±49
284 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 0.3 ~ 0.8 V is applied
to terminal VTA of the ECM. The voltage applied to the termi-
nals VTA of the ECM increases in proportion to the opening
angle of the throttle valve and becomes approximately 3.2 ~ 4.9
V when the throttle valve is fully opened. The ECM judges the
vehicle driving conditions from this signal input from terminal
VTA, and uses it 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 with more than 5 sec.:
(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.
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
DI00R±05

A03595
Throttle Position Sensor
ECM
E8
E8 1
3
2Y
LG
BR1
11
9VC
VTA
E25 V
*1: w/o Immobiliser
*2: w/ Immobiliser(*2)
E8 E810
(*1)
DI±50
± DIAGNOSTICSENGINE (5S±FE)
285 Author: Date:
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

If DTCs P0105 (Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction), P0106 (Man-
ifold Absolute Pressure /Barometric Pressure Circuit Range/Performance Problem), P0110 (Intake Air
Temp. Circuit Malfunction), P0115 (Engine Coolant Temp. Circuit Malfunction) and P0120 (Throttle/
Pedal Position Sensor/Switch ºAº Circuit Malfunction) 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.

FI7052
A00369
ON
VC (+)
± DIAGNOSTICSENGINE (5S±FE)
DI±51
286 Author: Date:
1 Connect OBD II scan tool or TOYOTA hand±held tester, read the 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. 70 %
Fully closedApprox. 10 %
OK Check for intermittent problems
(See page DI±3).
NG
2 Check voltage between terminal VC of throttle position sensor connector and
body ground.
PREPARATION:
(a) Disconnect the throttle position sensor connector.
(b) Turn the ignition switch ON.
CHECK:
Measure voltage between terminal VC of the throttle position
connector and body ground.
OK:
Voltage: 4.5 ~ 5.5 V
NG Go to step 5.
OK

A03013A03413
ON
VTA
(+)E2
(±)
w/o Immobiliser
w/ Immobiliser
VTA
(+)E2
(±)
DI±52
± DIAGNOSTICSENGINE (5S±FE)
287 Author: Date:
3 Check throttle position sensor (See page SF±29).
NG Replace throttle position sensor.
OK
4 Check voltage between terminals VTA and E2 of ECM connector.
PREPARATION:
(a) Remove the glove compartment (See page SF±64).
(b) Turn the ignition switch ON.
CHECK:
Measure voltage between terminals VTA and E2 of the ECM
connector.
OK:
Throttle valveVoltage
Fully closed0.3 ~ 1.0 V
Fully open3.2 ~ 4.9 V
NG Check for open and short in harness and con-
nector between ECM and throttle position sen-
sor (VTA or E2 line) (See page IN±31).
OK
Check and replace ECM (See page IN±31).

A03008A03414
ON
VC
(+) E2
(±)
w/o Immobiliser
w/ Immobiliser
VC
(+) E2
(±)
± DIAGNOSTICSENGINE (5S±FE)
DI±53
288 Author: Date:
5 Check voltage between terminals VC and E2 of ECM connector.
PREPARATION:
(a) Remove the glove compartment (See page SF±64).
(b) Turn 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 be-
tween ECM and sensor (VC line)
(See page IN±31).

DI±54
± DIAGNOSTICSENGINE (5S±FE)
289 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±49.
DTC No.Detection ItemTrouble 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.
DI00S±04

A00477
Atmosphere
Cover
Exhaust GasPlatinum
Electrode
Solid Electrolyte
(Zirconia Element)
Platinum
Electrode
Heater
Air±Fuel Ratio
(V)
2.6 4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.4
12 13 14 15 16 17 18
Coating (Ceramic)
ECM Monitored
A/F Sensor Voltage
19
± DIAGNOSTICSENGINE (5S±FE)
DI±55
290 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 exist-
ing 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 is not fully closed
Fuel system

Injector

Ignition system

Gas leakage on exhaust system

Open or short in A/F sensor circuit

A/F sensor

ECM
DI1JU±03

A03597
B±Y
FL
Block47
EFI
IGN
14 2
4 EFI
Relay
21
53
B±Y
BR
3
12 B
B
1
24 3 9
II3
J/CB
W±R
P±B
W
BG
P±B 56
2
5
1K
14
HT2 21 O 1W
E9E8
E9 E8
MAIN FLE8 1B
B 1ECMAF

OX2 HTAF
AF 1K
2F
E03 E1E04 A/F
Sensor
Engine Room R/B No.2
B±YJ19 J/C
2
1
II2II3
II3
EB
Heated
Oxygen
Sensor
(Bank 1
Sensor 2)
EC
Instrument
Panel J/B7
3 5
6
7
2L 2A
F611
F4
B±G
Battery B±R
2K
2J
W±B
3.3V
3.0V
AM2 B
W±R
J27
*1: w/o Immobiliser
*2: w/ Immobiliser
(*1)
(*2)
to Analog±Digital
Converter
E914 E8 13
(*1) (*2) J27
B±Y
B±Y
IG Switch
B±R
*3: California
(*6) (*3) (*6) (*3)
(*1)
2
MREL
E107
(*2)
EE
J27 J27
J/C
B BB±Y
II4
6
B±W(*2)
B±W(*2)
*5:TMC Made
*6:TMMK Made
L(*5)
(*3)
B±W(*5)
(*3)
BR
*4: Except California
DI±56
± DIAGNOSTICSENGINE (5S±FE)
291 Author: Date:
HINT:

After confirming DTC P0125, use the OBD II scan tool or TOYOTA hand-held tester to confirm voltage
output of A/F sensor from the CURRENT DATA.

The ECM controls the voltage of AF
and AF terminals of ECM to the fixed voltage. 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
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.

± DIAGNOSTICSENGINE (5S±FE)
DI±57
292 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 volt-
age output of A/F sensor.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(b) Warm up the A/F sensor with the engine at 2,500 rpm for approx. 90 sec.
CHECK:
Read voltage value of the A/F sensor on the screen of OBD II scan tool or TOYOTA hand±held tester when
you perform all the following conditions.
HINT:
The voltage of AF
terminal of ECM is 3.3 V fixed and the A/F terminal is 3.0 V fixed. Therefore, it is impos-
sible to check the A/F sensor output voltage at the terminals (AF
/AF) of ECM.
OK:
ConditionA/F Sensor Voltage Value
Engine idling
Engine racing
Not remains at 3.30 V (* 0.660 V)

Not remains at38V(*076V)ormoreDriving at engine speed 1,500 rpm or more and vehicle
speed 40 km/h (25 mph) or more, 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 the A/F sensor is below 2.8 V (* 0.56
V), it is normal.

During fuel cut, there is a case that the output voltage of the A/F sensor is above 3.8 V (* 0.76 V), it
is normal.

If output voltage of the A/F sensor remains at 3.30 V (* 0.660 V) even after performing all the above
conditions, A/F the sensor 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 sensor circuit may be short.
*: When you use the OBD II scan tool (excluding TOYOTA hand±held tester).
OK Go to step 10.
NG

DI±58
± DIAGNOSTICSENGINE (5S±FE)
293 Author: Date:
3 Check for open and short in harness and connector between ECM and A/F sen-
sor (See page IN±31).
NG Repair or replace harness or connector.
OK
4 Check resistance of A/F sensor heater (See page SF±59).
NG Replace A/F sensor.
OK
5 Check air induction system (See page SF±1).
NG Replace or replace.
OK
6 Check EGR system (See page EC±12).
NG Repair 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