2001 TOYOTA HIGHLANDER o2 sensor

- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-265
455 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P2121 THROTTLE/PEDAL POSITION
SENSOR/SWITCH ºDº CIRCUIT
RANGE/PERFORMANCE
HINT:
This is repair procedure for the ºaccelerator pedal position sensorº.
CIRCUIT DESCRIPTION
Refer to DTC P2120 on page 05-257.
DTC No.DTC Detection ConditionTrouble Area
P2121
Conditions (a) continue for 0.5 seconds:
(a) Difference between VPA and VPA2 exceeds the threshold
(1 trip detection logic)
Open or short in Accelerator pedal position sensor circuit

Accelerator pedal position sensor

ECM
MONITOR DESCRIPTION
The accelerator pedal position sensor is mounted on the accelerator pedal bracket. The accelerator pedal
position sensor has two sensor elements/signal outputs: VPA and VPA2. VPA is used to detect the actual
accelerator pedal angle (used for engine control) and VPA2 is used to detect malfunctions in VPA. When
the difference between the voltage outputs of VPA and VPA2 deviate from the standard, the ECM concludes
the accelerator pedal position sensor has a malfunction. The ECM turns on the MIL and a DTC is set.
FAIL-SAFE
The accelerator pedal position sensor has 2 (main and sub) sensor circuits. If a malfunction occurs in either
of the sensor circuits, the ECM detects the abnormal signal voltage difference between the 2 sensor circuits
and switches to fail-safe mode. In fail-safe mode, the remaining circuit is used to calculate the accelerator
pedal opening to allow the vehicle to continue driving.
If both circuits malfunction, the ECM regards the opening angle of the accelerator pedal to be fully closed.
In this case, the throttle valve will remain closed as if the engine is idling.
If a ºpassº condition is detected and then the ignition switch is turned OFF, the fail-safe operation will stop
and the system will return to normal condition.
MONITOR STRATEGY
Related DTCsP2121: TP sensor malfunction
Required sensors / components (Main)Accelerator position sensor
Required sensors / components (Related)-
Frequency of operationContinuous
Duration0.5 sec.
MIL operationImmediate
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
The monitor will run whenever this DTC is not presentSee page 05-16
Either of the following conditions is met:Condition 1 or 2
1. Electronic throttle actuator powerON
2. Ignition switchON
TYPICAL MALFUNCTION THRESHOLDS
Learned voltage value of (VTA1 - VTA2)Less than 0.4 V, or more than 1.2 V
05ITH-02

B53781
A67445A92629
A27
Accelerator Pedal
Position Sensor
VPA
EPA
VCPA
VPA2 EPA2 VCP2 Wire Harness Side
E5
ECM VPA
EPAVCPA
VPA2
EPA2VCP2
A53765
E5
ECM
VPA2 (+)
EPA2 (-)VPA (+)
EPA (-)
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-267
457 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
2 CHECK WIRE HARNESS (ACCELERATOR PEDAL POSITION SENSOR - ECM)
(a) Disconnect the A27 sensor connector.
(b) Disconnect the E5 ECM connector.
(c) Measure the resistance of the wire harness side connec-
tors.
Standard:
Tester ConnectionSpecified Condition
VPA (A27-6) - VPA (E5-22)
EPA (A27-5) - EPA (E5-28)
VCPA (A27-4) - VCPA (E5-26)
VPA2 (A27-3) - VPA2 (E5-23)
EPA2 (A27-2) - EPA2 (E5-29)
VCP2 (A27-1) - VCP2 (E5-27)
Below 1 W
VPA (A27-6) or VPA (E5-22) - Body ground
EPA (A27-5) or EPA (E5-28) - Body ground
VCPA (A27-4) or VCPA (E5-26) - Body ground
VPA2 (A27-3) or VPA2 (E5-23) - Body ground
EPA2 (A27-2) or EPA2 (E5-29) - Body ground
VCP2 (A27-1) or VCP2 (E5-27) - Body ground
10 kW or higher
NG REPAIR OR REPLACE HARNESS AND
CONNECTOR
OK
REPLACE ACCELERATOR PEDAL ROD ASSY (See page 10-1 1)
OBD II scan tool (excluding hand-held tester):
1 INSPECT ECM (VPA AND VPA2 VOLTAGE)
(a) Turn the ignition switch ON.
(b) Measure the voltage between the specified terminals of
the E5 ECM connector.
Standard:
Tester ConnectionTester Connection
Accelerator Pedal PositionVPA (E5-22)
- EPA (E5-28)VPA2 (E5-23)
- EPA2 (E5-29)
Released0.5 to 1.1 V1.2 to 2.0 V
Depressed2.6 to 4.5 V3.4 to 5.3 V
OK REPLACE ECM (See page 10-9)
NG

B53781
A67445A92629
A27
Accelerator Pedal
Position Sensor
VPA
EPA
VCPA
VPA2 EPA2 VCP2 Wire Harness Side
E5
ECM VPA
EPAVCPA
VPA2
EPA2VCP2
05-268
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
458 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
2 CHECK WIRE HARNESS (ACCELERATOR PEDAL POSITION SENSOR - ECM)
(a) Disconnect the A27 sensor connector.
(b) Disconnect the E5 ECM connector.
(c) Measure the resistance of the wire harness side connec-
tors.
Standard:
Tester ConnectionSpecified Condition
VPA (A27-6) - VPA (E5-22)
EPA (A27-5) - EPA (E5-28)
VCPA (A27-4) - VCPA (E5-26)
VPA2 (A17-3) - VPA2 (E5-23)
EPA2 (A27-2) - EPA2 (E5-29)
VCP2 (A27-1) - VCP2 (E5-27)
Below 1 W
VPA (A27-6) or VPA (E5-22) - Body ground
EPA (A27-5) or EPA (E5-28) - Body ground
VCPA (A27-4) or VCPA (E5-26) - Body ground
VPA2 (A27-3) or VPA2 (E5-23) - Body ground
EPA2 (A27-2) or EPA2 (E5-29) - Body ground
VCP2 (A27-1) or VCP2 (E5-27) - Body ground
10 kW or higher
NG REPAIR OR REPLACE HARNESS AND
CONNECTOR
OK
REPLACE ACCELERATOR PEDAL ROD ASSY (See page 10-1 1)

A73819
AtomosphereSolid Electrolyte
(Zirconia Element)
Platinum
Electrode HeaterExhaust Gas
Cover Element
A
A
ECM Monitored
A/F Sensor Voltage
Air-Fuel Ratio Alumina
A - A Section
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-269
459 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P2195 OXYGEN (A/F) SENSOR SIGNAL STUCK
LEAN (BANK 1 SENSOR 1)
DTC P2196 OXYGEN (A/F) SENSOR SIGNAL STUCK
RICH (BANK 1 SENSOR 1)
HINT:
Although the title (DTC description) says ºoxygen sensorº, this DTC is related to the ºA/F sensorº.
CIRCUIT DESCRIPTION
The Air-Fuel ratio (A/F) sensor provides output voltage* approximately equal 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.
With the A/F sensor output, the ECM can determine deviation from the stoichiometric air-fuel ratio and con-
trol proper injection time. If the A/F sensor is malfunctioning, the ECM is unable to accurately control air-fuel
ratio.
The A/F sensor is equipped with a heater which heats the zirconia element. The heater is also controlled
by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows
to the heater which heats the sensor to facilitate detection of accurate oxygen concentration.
The A/F sensor is a planar type. Compared to a conventional type, the sensor and heater portions are nar-
rower. Because the heat of the heater is conducted through the alumina to zirconia (of the sensor portion),
sensor activation is accelerated.
To obtain a high purification rate of the CO, HC and NOx components of the exhaust gas, a three-way cata-
lytic converter is used. The converter is most efficient when the air-fuel ratio is maintained near the stoichio-
metric air-fuel ratio.
HINT:
*: The voltage value changes on the inside of the ECM only.
05EVX-06

05-270
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
460 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)DTC No.
DTC Detection ConditionTrouble Area
P2195
Conditions (a) and (b) continue for 2 seconds or more:
(a) A/F sensor voltage is more than 3.8 V
(b) Rear oxygen sensor voltage is 0.15 V or more
(2 trip detection logic)

Open or short in A/F sensor circuit

A/F sensor

A/F sensor heater

EFI relay

Open or short in A/F sensor heater and EFI relay circuits

Air induction system

Fuel pressure

Injector

ECM
P2196
Conditions (a) and (b) continue for 2 seconds or more:
(a) A/F sensor voltage is less than 2.8 V
(b) Rear oxygen sensor voltage is less than 0.85 V
(2 trip detection logic)

Same as DTC No. P2195
HINT:

DTCs P2195 and P2196 indicate a malfunction related to bank 1 of the A/F sensor circuit.

Sensor 1 is the sensor closest to the engine assembly.

After confirming DTC P2195 and P2196, use the hand-held tester or the OBD II scan tool to confirm
A/F sensor output voltage (AFS B1S1) from the ALL menu (to reach the ALL menu: DIAGNOSIS / EN-
HANCED OBD II / DATA LIST / ALL).

The A/F sensor's output voltage and the short-term fuel trim value can be read using the OBD II scan
tool or the hand-held tester.

The ECM controls the voltage of the A1A+ and A1A- terminals of the ECM to a fixed voltage. There-
fore, it is impossible to confirm the A/F sensor output voltage without the OBD II scan tool or the hand-
held tester.

The OBD II scan tool (excluding hand-held tester) displays one fifth of the A/F sensor output voltage
which is displayed on the hand-held tester.
MONITOR DESCRIPTION
Under the air-fuel ratio feedback control, if the voltage output of the A/F sensor indicates RICH or LEAN for
more than a certain period of time, the ECM concludes that there is a fault in the A/F sensor system. The
ECM will turn on the MIL and will set a DTC.
Example:
If the A/F sensor voltage output is less than 2.8 V (very RICH) for 10 seconds even though voltage output
of the heated oxygen sensor output voltage is less than 0.85 V, the ECM sets DTC P2196 or DTC P2198.
If the heated oxygen sensor output voltage is 0.15 V or more but the A/F sensor voltage output is more than
3.8 V (very LEAN) for 10 seconds, DTC P2195 is set.
MONITOR STRATEGY
Related DTCsP2195: A/F Sensor Signal (Bank 1) Stuck Lean
P2196: A/F Sensor Signal (Bank 1) Stuck Rich
Required sensors / components (Main)A/F sensor
Required sensors / components (Related)Rear HO2S
Frequency of operationContinuous
Duration10 sec.
MIL operation2 driving cycles
Sequence of operationNone

- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-271
461 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
TYPICAL ENABLING CONDITIONS
The monitor will run whenever these DTCs are not presentSee page 05-16
Time after engine start30 sec. or more
A/F sensor statusActivated
Fuel system statusClosed Loop
Engine conditionRunning
TYPICAL MALFUNCTION THRESHOLDS
P2195:
Both of the following conditions are met:-
A/F sensor voltageMore than 3.8 V
Rear HO2S voltage0.15 V or more
P2196:
Both of the following conditions are met:-
A/F sensor voltageLess than 2.8 V
Rear HO2S voltageLess than 0.85 V

A90305
23
A1A-
MREL
AHA1A
A1A+ECM
2D31
8 B-W
B-R
E8
E8
E5E8
W-B
BRBR
B Y
11
F7
FL Block
AssyEFI
RelayA6
A/F Sensor
J7
J/C Engine
Room J/B
A 1
43 2
2
3
FL
Main
Battery
EHShielded
Engine
Room R/B
No. 25
EE 3
2 5
1HT
AF- AF+ +B
A
E91
E1 B-W
WBR IK3 EB1
EFI
NO. 22
2
1
Y13
P-L
EFI
NO. 15 3
2F 2B
2I
J2
J/C A 34
W 05-272
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
462 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
WIRING DIAGRAM

A79199
Vehicle Speed
38 to 75 mph
(60 to 120 km/h)
Idling
Ignition Switch OFF
3 to 5 minutes
Time 2 minutes
(a), (b)(c)(d)
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-273
463 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
CONFIRMATION DRIVING PATTERN
(a) Connect the hand-held tester to the DLC3.
(b) Switch the hand-held tester from normal mode to check mode (see page 05-40).
(c) Start the engine and warm it up with all the accessory switched OFF.
(d) Drive the vehicle at 38 to 75 mph (60 to 120 km/h) and engine speed at 1,400 to 3,200 rpm for 3 to
5 minutes.
HINT:
If a malfunction exists, the MIL will be illuminated during step (d).
NOTICE:
If the conditions in this test are not strictly followed, detection of a malfunction will not occur. If you
do not have a hand-held tester, turn the ignition switch OFF after performing steps (c) and (d), then
perform steps (c) and (d) again.
INSPECTION PROCEDURE
HINT:
Hand-held tester only:
It is possible the malfunctioning area can be found using the ACTIVE TEST A/F CONTROL operation. The
A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble
areas are malfunctioning or not.
(a) Perform the ACTIVE TEST A/F CONTROL operation.
HINT:
The A/F CONTROL operation lowers the injection volume 12.5 % or increases the injection volume 25 %.
(1) Connect the hand-held tester to the DLC3 on the vehicle.
(2) Turn the ignition switch ON.
(3) Warm up the engine by running the engine at 2,500 rpm for approximately 90 seconds.
(4) Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
(5) Perform the A/F CONTROL operation with the engine idle (press the right or left button).
Result:
A/F sensor reacts in accordance with increase and decrease of injection volume:
+25 % " RICH output: Less than 3.0 V
-12.5 % " LEAN output: More than 3.35 V
Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25 % " RICH output: More than 0.55 V
-12.5 % " LEAN output: Less than 0.4 V