2001 TOYOTA SEQUOIA fuel

± 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.

A23456
Air±fuel Ratio Sensor Current Monitor:
Fuel±cut
High Side Thresh
Low Side Thresh
3 sec. or more
Time t2
t1 3 sec.
Delay ON
OFF
Normal
Malfunction3 sec.
Delay3 sec.
Delay Sensor Current
(mA)
A/F Sensor
Current
Cumulative Time = t1 + t2 = 3 sec. or more DI±386
± DIAGNOSTICSENGINE
580 Author: Date:
2005 SEQUOIA (RM1146U)
MONITOR DESCRIPTION

Sensor voltage detection monitor:
Under the air±fuel ratio feedback control, if the A/F sensor voltage output indicates rich or lean for a
certain period of time, the ECM determines that there is a malfunction in the A/F sensor. The ECM illu-
minates the MIL and sets a DTC.
Example:
If the A/F sensor voltage output is less than 2.8 V (very rich condition) for 10 seconds, despite the HO2
sensor voltage output being less than 0.85 V, the ECM sets DTC P2196. Alternatively, if the A/F sensor
voltage output is more than 3.8 V (very lean condition) for 10 seconds, despite the HO2 sensor voltage
output being 0.15 V or more, DTC P2195 or P2197 is set.

Sensor current detection monitor:
A rich air±fuel mixture causes a low air±fuel ratio sensor current, and a lean air fuel mixture causes
a high air fuel ratio sensor current. Therefore, the sensor output becomes high during acceleration,
and the sensor becomes low during deceleration.
The ECM monitors the air±fuel ratio sensor current during fuel±cut and detects an unusual current val-
ue. If the cumulative time the sensor output is out of range exceeds more than 3 seconds, the ECM
interprets a malfunction in the air±fuel ratio sensor and sets a DTC.

± DIAGNOSTICSENGINE
DI±387
581 Author: Date:
2005 SEQUOIA (RM1146U)
MONITOR STRATEGY
P2195A/F sensor (Bank 1) signal stuck leanP2195A/F sensor (Bank 1) current (high side)
P2196A/F sensor (Bank 1) signal stuck rich
RltdDTC
P2196A/F sensor (Bank 1) current (low side)Related DTCs
P2197A/F sensor (Bank 2) signal stuck leanP2197A/F sensor (Bank 2) current (high side)
P2198A/F sensor (Bank 2) signal stuck richP2198A/F sensor (Bank 2) current (low side)
Required sensors/componentsA/F sensor
Frequency of operationOnce per driving cycle
Duration15 sec.: A/F sensor signal stuck lean/rich
3 sec.: A/F sensor current (high/low side)
MIL operation2 driving cycles
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
ItSpecificationItemMinimumMaximum
The monitor will run whenever these
DTCs are not presentSee page DI±18
P2195, P2197 (A/F sensor signal stuck lean):
Duration while all of following conditions
met2 sec.±
Rear HO2S voltage0.15 V±
Time after engine start30 sec.±
A/F sensor statusActivated
Fuel system statusClosed±loop
EngineRunning
P2196, P2198 (A/F sensor signal stuck rich):
Duration while all of following conditions
met2 sec.±
Rear HO2S voltage±0.6 V
Time after engine start30 sec.±
A/F sensor statusActivated
Fuel system statusClosed±loop
EngineRunning
P2195, P2197 (A/F sensor current (High side)):
Battery voltage11 V±
ECT75°C (167°F)±
Atmospheric pressure/760 mmHg0.75±
A/F sensor statusActivated
Continuous time of fuel±cut3 to 10 sec.
P2196, P2198 (A/F sensor current (Low side)):
Battery voltage11 V±
ECT75°C (167°F)±

DI±388
± DIAGNOSTICSENGINE
582 Author: Date:
2005 SEQUOIA (RM1146U) Atmospheric pressure/760 mmHg
0.75±
A/F sensor statusActivated
Continuous time of fuel±cut3 to 10 sec.
TYPICAL MALFUNCTION THRESHOLDS
Detection CriteriaThreshold
P2195, P2197 (A/F sensor signal stuck lean):
A/F sensor voltageMore than 3.8 V for 15 sec.
P2196, P2198 (A/F sensor signal stuck rich):
A/F sensor voltageLess than 2.8 V for 15 sec.
P2195, P2197 (A/F sensor current (High side)):
Duration of the following condition3 sec. or more
A/F sensor current3.6 mA or more
P2196, P2198 (A/F sensor current (Low side)):
Duration of the following condition3 sec. or more
A/F sensor currentLess than 1.4 mA
MONITOR RESULT
Refer to page DI±26 for detailed information.
The test value and test limit information are described as shown in the following table. Check the monitor
result and test values after performing the monitor drive pattern (refer to ºConfirmation Monitorº).

MID (Monitor Identification Data) is assigned to each emissions±related component.

TID (Test Identification Data) is assigned to each test value.
A/F sensor bank 1 sensor 1
MIDTIDScalingDescription of Test ValueMinimum Test LimitMaximum Test Limit
$01$91Multiply by 0.003906
(mA)A/F currentMinimum test limitMaximum test limit
A/F sensor bank 2 sensor 1
MIDTIDScalingDescription of Test ValueMinimum Test LimitMaximum Test Limit
$05$91Multiply by 0.003906
(mA)A/F currentMinimum test limitMaximum test limit

A23662
40 mph (64 km/h)
Idling
IG SW OFF ECT:
75C (167F) or higher
Vehicle Speed
Warming up(d)(f)
10 minutes
or more(g)
10 seconds
or more4 seconds
or moreTime At Least 3 times
(h) (i)
(j) Accelerator Pedal
DepressedAccelerator Pedal
Released (Fuel±cut)
DI±390
± DIAGNOSTICSENGINE
584 Author: Date:
2005 SEQUOIA (RM1146U)
CONFIRMATION DRIVING PATTERN
HINT:
This confirmation driving pattern is used in steps 2, 4, 7, 17 and 21 of the following diagnostic troubleshooting
procedure when using a hand±held tester.
(a) Connect the hand±held tester to DLC3.
(b) Turn the ignition switch to ON and turn the tester ON.
(c) Clear DTCs (see page DI±43).
(d) Start the engine, and warm it up until the ECT reaches 75C (167F) or higher.
(e) On the hand±held tester, select the following menu items: DIAGNOSIS/ENHANCED OBD II/DATA
LIST/FC IDL.
(f) Drive the vehicle at 40 mph (64 km/h) or more for at least 10 minutes.
(g) Change the transmission to 2nd gear.
(h) Drive the vehicle at proper vehicle speed to perform fuel±cut operation.
HINT:
Fuel±cut is performed under following conditions met:

Accelerator pedal fully released.

Engine speed 2,500 rpm or more (fuel injection returns at 1,000 rpm).
(i) Accelerate the vehicle to 30 mph (48 km/h) or more by depressing the accelerator pedal for at least
10 seconds.
(j) Soon after performing step (8) above, release the accelerator pedal for at least 4 seconds without de-
pressing the brake pedal, in order to execute fuel±cut control.
(k) Stop the vehicle and allow the engine to idle for 10 seconds or more.
(l) Allow the vehicle to decelerate until the vehicle speed declines to less than 6 mph (10 km/h).
(m) Repeat steps from (8) through (10) above at least 3 times in one driving cycle.
HINT:
Completing all A/F sensor monitors are required to change the value in TEST RESULT.
CAUTION:
Strictly observe of posted speed limits, traffic laws, and road conditions when performing these
drive pattern.

± DIAGNOSTICSENGINE
DI±391
585 Author: Date:
2005 SEQUOIA (RM1146U)
INSPECTION PROCEDURE
HINT:
Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE
TEST. The A/F CONTROL function can help to determine whether the Air±Fuel Ratio (A/F) sensor, Heated
Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.
The following instructions describe how to conduct the A/F CONTROL operation using a hand±held tester.
(1) Connect a hand±held tester to the DLC3.
(2) Start the engine and turn the tester ON.
(3) Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
(4) On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE
TEST / A/F CONTROL.
(5) Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT
or LEFT button to change the fuel injection volume).
(6) Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 (AFS B2S1) and OS2 B1S2
(O2S B2S2)) displayed on the tester.
HINT:

The A/F CONTROL operation lowers the fuel injection volume by 12.5 % or increases the injection
volume by 25 %.

Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
Standard:
Tester Display
(Sensor)Injection VolumesStatusVoltages
AFS B1S1 (AFS B2S1)
(A/F)+25 %RichLess than 3.0
AFS B1S1 (AFS B2S1)
(A/F)±12.5 %LeanMore than 3.35
O2S B1S2 (O2S B2S2)
(HO2)+25 %RichMore than 0.55
O2S B1S2 (O2S B2S2)
(HO2)±12.5 %LeanLess than 0.4