2001 TOYOTA SEQUOIA O2 sensor

A21022
Wire Harness Side:
A37
Accelerator Pedal Position Sensor
VCP2
EPA2
VPA2
VCPAEPAVPA
B17417
E4VPA2
VCPAVPA
EPA2
EPAVCP2
± DIAGNOSTICSENGINE
DI±377
571 Author: Date:
2005 SEQUOIA (RM1146U)
2 Check for open and short in harness and connector in VCPA, VCP2, VPA, VPA2
EPA and EPA2 circuit between ECM and accelerator pedal position sensor.
PREPARATION:
(a) Disconnect the A37 accelerator pedal position sensor
connector.
(b) Disconnect the E4 ECM connector.
CHECK:
Measure the resistance between the wire harness side connec-
tors.
OK:
Standard:
Tester ConnectionSpecified Condition
VPA (A37±6) ± VPA (E4±18)Below 1 W
EPA (A37±5) ± EPA (E4±20)Below 1 W
VCPA (A37±4) ± VCPA (E4±26)Below 1 W
VPA2 (A37±3) ± VPA2 (E4±19)Below 1 W
EPA2 (A37±2) ± EPA2 (E4±21)Below 1 W
VCP2 (A37±1) ± VCP2 (E4±27)Below 1 W
VPA (A37±6) or VPA (E4±18) ±
Body ground10 kW or higher
EPA (A37±5) or EPA (E4±20) ±
Body ground10 kW or higher
VCPA (A37±4) or VCPA (E4±26) ±
Body ground10 kW or higher
VPA2 (A37±3) or VPA2 (E4±19) ±
Body ground10 kW or higher
EPA2 (A37±2) or EPA2 (E4±21) ±
Body ground10 kW or higher
VCP2 (A37±1) or VCP2 (E4±27) ±
Body ground10 kW or higher
NG Repair or replace harness and connector.
OK

B17448
EPA (±)VCPA (+)
EPA2 (±)
VCP2 (+) Accelerator Pedal
Position Sensor
Connector
E4
A37
DI±378
± DIAGNOSTICSENGINE
572 Author: Date:
2005 SEQUOIA (RM1146U)
3 Check voltage between terminals VCPA and EPA, and VCP2 and EPA2 of ECM
terminals.
PREPARATION:
(a) Turn the ignition switch ON.
(b) Disconnect the A37 accelerator pedal position sensor
connector.
CHECK:
Measure the voltage between the specified terminals of the E4
ECM connector.
OK:
Standard:
Tester ConnectionSpecified Condition
VCPA (E4±26) ± EPA (E4±20)4.5 to 5.5 V
VCP2 (E4±27) ± EPA2 (E4±21)4.5 to 5.5 V
NG Replace ECM (See page SF±80).
OK
4 Replace accelerator pedal assembly (See page SF±78).
Go

DI±380
± DIAGNOSTICSENGINE
574 Author: Date:
2005 SEQUOIA (RM1146U)
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 DI±370.
DTC No.DTC Detecting ConditionTrouble Area
P2121
Conditions (a) and (b) continue for 0.5 seconds:
(a) Difference between VPA and VPA2 exceeds the threshold
(b) IDL is OFF
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 2 sensor elements/signal outputs: VPA1 and VPA2. VPA1 is used to detect the actual
accelerator pedal angle (used for engine control) and VPA2 is used to detect malfunctions in VPA1. When
the difference between the voltage outputs of VPA1 and VPA2 deviates from the standard, the ECM con-
cludes 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 two (main and sub) sensor circuits. If a malfunction occurs in ei-
ther of the sensor circuits, the ECM detects the abnormal signal voltage difference between the two sensor
circuits and switches to limp mode. In limp 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 DTCsP2121Accelerator position sensor (rationality)
Required sensors/componentsAccelerator position sensor
Frequency of operationContinuous
Duration0.5 sec.
MIL operationImmediate
Sequence of operationNone
DID8H±01

FI7052DepressedReleased
± DIAGNOSTICSENGINE
DI±381
575 Author: Date:
2005 SEQUOIA (RM1146U)
TYPICAL ENABLING CONDITIONS
ItSpecificationItemMinimumMaximum
The monitor will run whenever this DTC is
not presentSee page DI±18
Either of the following conditions is metCondition 1 or 2
1. Ignition switchON
2. Throttle control motor powerON
TYPICAL MALFUNCTION THRESHOLDS
Detection CriteriaThreshold
Difference between VPA1 voltage (learned value) and VPA2
voltage (learned value)Less than 0.4 V, or more than 1.2 V
WIRING DIAGRAM
Refer to DTC P2120 on page DI±370.
INSPECTION PROCEDURE
HINT:
Read freeze frame data using the hand-held tester. Freeze frame data records the engine conditions when
a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was
running or stopped, if the engine was warmed up or not, if the air±fuel ratio was lean or rich, as well as other
data from the time when a malfunction occurred.
1 Connect hand±held tester, and read the voltage for accelerator pedal position
sensor data.
PREPARATION:
(a) Connect the hand±held tester to the DLC3.
(b) Turn the ignition switch ON and push the hand±held tes-
ter main switch ON.
(c) Enter the following menu: DIAGNOSIS / ENHANCED
OBD II / DATA LIST / ETCS / ACCEL POS #1 and ACCEL
POS #2.
CHECK:
Read the voltage for the accelerator pedal position sensor data.
OK:
Standard:
Accelerator pedalACCEL POS #1ACCEL POS #2
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 SF±80).
NG

A21022
Wire Harness Side:
A37
Accelerator Pedal Position Sensor
VCP2
EPA2
VPA2
VCPAEPAVPA
B17417
E4VPA2
VCPAVPA
EPA2
EPAVCP2
DI±382
± DIAGNOSTICSENGINE
576 Author: Date:
2005 SEQUOIA (RM1146U)
2 Check for open and short in harness and connector between accelerator pedal
position sensor and ECM.
PREPARATION:
(a) Disconnect the A37 accelerator pedal position sensor
connector.
(b) Disconnect the E4 ECM connector.
CHECK:
Measure the resistance between the wire harness side connec-
tors.
OK:
Standard (Check for open):
Tester ConnectionSpecified Condition
VPA (A37±6) ± VPA (E4±18)Below 1 W
EPA (A37±5) ± EPA (E4±20)Below 1 W
VCPA (A37±4) ± VCPA (E4±26)Below 1 W
VPA2 (A37±3) ± VPA2 (E4±19)Below 1 W
EPA2 (A37±2) ± EPA2 (E4±21)Below 1 W
VCP2 (A37±1) ± VCP2 (E4±27)Below 1 W
Standard (Check for short):
Tester ConnectionSpecified Condition
VPA (A37±6) or VPA (E4±18) ±
Body ground10 kW or higher
EPA (A37±5) or EPA (E4±20) ±
Body ground10 kW or higher
VCPA (A37±4) or VCPA (E4±26) ±
Body ground10 kW or higher
VPA2 (A37±3) or VPA2 (E4±19) ±
Body ground10 kW or higher
EPA2 (A37±2) or EPA2 (E4±21) ±
Body ground10 kW or higher
VCP2 (A37±1) or VCP2 (E4±27) ±
Body ground10 kW or higher
NG Repair or replace harness or connector.
OK
Replace accelerator pedal pedal assembly.

± DIAGNOSTICSENGINE
DI±383
577 Author: Date:
2005 SEQUOIA (RM1146U)
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)
DTC P2197 Oxygen (A/F) Sensor Signal Stuck Lean
(Bank 2 Sensor 1)
DTC P2198 Oxygen (A/F) Sensor Signal Stuck Rich
(Bank 2 Sensor 1)
HINT:

Although the DTC titles say oxygen sensor, these DTCs relate to the Air±Fuel Ratio (A/F) sensor.

Sensor 1 refers to the sensor mounted in front of the Three±Way Catalytic Converter (TWC) and lo-
cated near the engine assembly.
DIDFT±01

A23473A±A Cross SectionAtmospheric AirSolid Electrolyte
(Zirconia Element)
Platinum
Electrode Heater
Exhaust Gas
Cover Element
A
A
ECM Monitored
A/F Sensor Voltage
Air±Fuel Ratio Alumina
4.0
3.0
2.0
12 13 14 15 16 17
DI±384
± DIAGNOSTICSENGINE
578 Author: Date:
2005 SEQUOIA (RM1146U)
CIRCUIT DESCRIPTION
The A/F sensor generates a voltage* that corresponds to the actual air±fuel ratio. This sensor voltage is used
to provide the ECM with feedback so that it can control the air±fuel ratio. The ECM determines the deviation
from the stoichiometric air±fuel ratio level, and regulates the fuel injection time. If the A/F sensor malfunc-
tions, the ECM is unable to control the air±fuel ratio accurately.
The A/F sensor is the planar type and is integrated with the heater, which heats the solid electrolyte (zirconia
element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas tempera-
ture is low), a current flows into the heater to heat the sensor, in order to facilitate accurate air±fuel ratio
detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat
generated by the heater is conducted to the solid electrolyte though the alumina, therefore the sensor activa-
tion is accelerated.
In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide
(NOx) components in the exhaust gas, a TWC is used. For the most efficient use of the TWC, the air±fuel
ratio must be precisely controlled so that it is always close to the stoichiometric level.
*: Value changes inside the ECM. Since the A/F sensor is the current output element, a current is converted
to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a
constant voltage.

± DIAGNOSTICSENGINE
DI±385
579 Author: Date:
2005 SEQUOIA (RM1146U)DTC No.
DTC Detection ConditionsTrouble Areas
P2195
P2197While fuel±cut operation performing (during vehicle decelera-
tion), air±fuel ratio sensor current is 3.6 mA or more for 3 se-
conds.
A/F sensor (sensor 1)

ECM
P2195
Conditions (a) and (b) continue for 2 seconds or more
(2 trip detection logic):
(a) Air±Fuel Ratio (A/F) sensor voltage more than 3.8 V
(b) Heated Oxygen (HO2) sensor voltage 0.15 V or more

Open or short in A/F sensor (sensor 1) circuit

A/F sensor (sensor 1)

A/F sensor (sensor 1) heater

EFI relay

A/F sensor heater and relay circuits

Air induction system

Fuel pressure

Injector

ECM
P2196
P2198While fuel±cut operation performing (during vehicle decelera-
tion), air±fuel ratio sensor current is less than 1.4 mA for 3
seconds.
A/F sensor (sensor 1)

ECM
P2196
Conditions (a) and (b) continue for 2 seconds or more
(2 trip detection logic):
(a) A/F sensor voltage less than 2.8 V
(b) HO2 sensor voltage less than 0.85 V

Open or short in A/F sensor (sensor 1) circuit

A/F sensor (sensor 1)

A/F sensor (sensor 1) heater

EFI relay

A/F sensor heater and relay circuits

Air induction system

Fuel pressure

Injector

ECM
HINT:

When any of these DTCs are set, check the A/F sensor voltage output by selecting the following menu
items on a hand-held tester: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / AFS B1S1.

Short-term fuel trim values can also be read using a hand-held tester.

The ECM regulates the voltage at the A1A+ and A1A± terminals of the ECM at a constant level. There-
fore, the A/F sensor voltage output cannot be confirmed without using a hand±held tester.

If the A/F sensor functional malfunction is detected, the ECM sets this DTC.