o2 sensor TOYOTA HIGHLANDER 2001 Service Repair Manual

A72304
Engine
RPMEngine
RPM (1) Idle (2) Approximately 2,500 rpm
Fuel Cut
When A/F sensor circuit is malfunctioning,
voltage output does not change A/F
Sensor
Voltage A/F
Sensor
Voltage
(1) Idle
Fuel Cut (3) Approximately 4,000 rpm
ºCondition (1), (2)º
Change of approximately 3.3 V Normal Condition
Malfunction Condition
ºCondition (3)º
3.8 V or More(1) Idle (2) Approximately 2,500 rpm(3) Approximately 4,000 rpm
(1) Idle
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HINT:

Whenever the A/F sensor output voltage remains at approximately 3.3 V (0.660 V)* (see ºMalfunction
Conditionº graphic) under any condition as well as the above conditions, the A/F sensor may have an
open circuit. This will happen also when the A/F sensor heater has an open circuit.

Whenever the A/F sensor output voltage remains at a certain value of approximately 3.8 V (0.76 V)*
or more, or 2.8 V (0.56 V)* or less (see ºMalfunction Conditionº graphic) under any condition as well
as the above conditions, the A/F sensor may have a short circuit.

The ECM will stop fuel injection (fuel is cut) during engine deceleration. This will cause a LEAN condi-
tion and should result in a momentary increase in the A/F sensor output voltage.

The ECM must establish a closed throttle position learned value to perform fuel cut. If the battery termi-
nal has been disconnected, the vehicle must be driven over 10 mph (16 km/h) to allow the ECM to learn
the closed throttle position.

When the vehicle is driven:
The output voltage of the A/F sensor may be below 2.8 V (0.76 V)* during fuel enrichment. For the
vehicle, this translates to a sudden increase in speed with the accelerator pedal fully depressed when
trying to overtake another vehicle. The A/F sensor is functioning normally.

The A/F sensor is a current output element, and therefore the current is converted into voltage inside
the ECM. If measuring voltage at connectors of A/F sensor or ECM, you will observe a constant volt-
age.
*: Voltage when using the OBD II scan tool.
OK Go to step 13
NG

A52607
AF-AF+
A6
A/F sensor
B60778
5
12 312
5
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3 INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
(a) Disconnect the A6 A/F sensor connector.
(b) Measure the resistance of the A/F sensor terminals.
Standard:
Tester ConnectionConditionSpecified Condition
1 (HT) - 2 (+B)20C (68F)1.8 to 3.4 W
1 (HT) - 4 (AF-)-10 kW or higher
NG REPLACE AIR FUEL RATIO SENSOR
OK
4 INSPECT RELAY (EFI)
(a) Remove the EFI relay from the engine room J/B.
(b) Measure the resistance of the EFI relay.
Standard:
Tester ConnectionSpecified Condition
3 - 510 kW or higher
3 - 5Below 1 W
(when battery voltage is applied to terminals 1 and 2)
NG REPLACE RELAY
OK

12
34
A76787
A81695A86849
Wire Harness Side
A6
A/F Sensor
HT
+B
E8
ECM
HA1A
AF+AF-
A1A-A1A+
A90346
A/F Sensor
EFI Relay
Heater
Sensor
A1A+ HA1A
Duty
Control ECM
From
Battery
A1A-
MREL Reference
+B
AF-AF+ HT
EFI NO. 1
FuseEFI NO. 2
Fuse
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5 CHECK WIRE HARNESS (A/F SENSOR - ECM)
(a) Check the wire harness between the ECM and A/F sen-
sor.
(1) Disconnect the A6 A/F sensor connector.
(2) Disconnect the E8 ECM connector.
(3) Measure the resistance of the wire harness side
connectors.
Standard:
Tester ConnectionSpecified Condition
A6-3 (AF+) - E8-23 (A1A+)
A6-4 (AF-) - E8-31 (A1A-)
A6-1 (HT) - E8-5 (HA1A)
Below 1 W
A6-3 (AF+) or A1A+ (E8-23) - Body ground
A6-4 (AF-) or A1A- (E8-31) - Body ground
A6-1 (HT) or HA1A (E8-5) - Body ground
10 kW or higher
NG REPAIR OR REPLACE HARNESS AND
CONNECTOR
OK

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6 CHECK AIR INDUCTION SYSTEM
(a) Check for vacuum leaks in the air induction system.
OK: No leak in the air induction system.
NG REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK
7 CHECK FUEL PRESSURE (See page 11-4)
(a) Check fuel pressure (high or low fuel pressure).
Standard:
ItemSpecified Condition
Fuel pressure304 to 343 kPa (3.1 to 3.5 kgf/cm2, 44 to 55 psi)
NG REPAIR OR REPLACE FUEL SYSTEM
OK
8 INSPECT FUEL INJECTOR ASSY (See page 11-7)
(a) Check injector injection (high or low fuel injection quantity or poor injection pattern).
Standard:
Injection VolumeDifference Between Each Injector
76 to 91 cm3 (4.6 to 5.5 cu in.)/15 seconds15 cm3 (0.9 cu in.) or less
NG REPLACE FUEL INJECTOR ASSY
(See page 11-10)
OK
9 REPLACE AIR FUEL RATIO SENSOR
GO
10 PERFORM CONFIRMATION DRIVING PATTERN
HINT:
Clear all DTCs prior to performing the confirmation driving pattern.
GO

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11 READ OUTPUT DTC
(a) Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
DisplayProceed to
A/F sensor circuit DTC are not outputA
A/F sensor circuit DTC are outputB
B REPLACE ECM (See page 10-9) AND PERFORM
CONFIRMATION DRIVING PATTERN
A
12 CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
OK: Vehicle has run out of fuel in past.
NO CHECK FOR INTERMITTENT PROBLEMS
(See page 05-9)
YES
DTC IS CAUSED BY RUNNING OUT OF FUEL
13 PERFORM CONFIRMATION DRIVING PATTERN
HINT:
Clear all DTCs prior to performing the confirmation driving pattern.
GO
14 GO TO RELEVANT DTC CHART (A/F SENSOR DTC OUTPUT AGAIN)
(a) Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
DisplayProceed to
A/F sensor circuit DTC are outputA
A/F sensor circuit DTC are not outputB
B Go to step 18
A
15 REPLACE AIR FUEL RATIO SENSOR
GO
16 PERFORM CONFIRMATION DRIVING PATTERN
HINT:
Clear all DTCs prior to performing the confirmation driving pattern.
GO

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17 READ OUTPUT DTC (A/F SENSOR DTC OUTPUT AGAIN)
(a) Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
DisplayProceed to
A/F sensor circuit DTC are not outputA
A/F sensor circuit DTC are outputB
B REPLACE ECM (See page 10-9) AND PERFORM
CONFIRMATION DRIVING PATTERN
A
18 CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
OK: Vehicle has run out of fuel in past.
NO CHECK FOR INTERMITTENT PROBLEMS
(See page 05-9)
YES
DTC IS CAUSED BY RUNNING OUT OF FUEL

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DTC P2238 OXYGEN SENSOR PUMPING CURRENT
CIRCUIT LOW (FOR A/F SENSOR)(BANK 1
SENSOR 1)
DTC P2239 OXYGEN SENSOR PUMPING CURRENT
CIRCUIT HIGH (FOR A/F SENSOR)(BANK 1
SENSOR 1)
DTC P2252 OXYGEN SENSOR REFERENCE GROUND
CIRCUIT LOW (FOR A/F SENSOR)(BANK 1
SENSOR 1)
DTC P2253 OXYGEN SENSOR REFERENCE GROUND
CIRCUIT HIGH (FOR A/F SENSOR)(BANK 1
SENSOR 1)
HINT:
Although the title (DTC description) says ºoxygen sensorº, this DTC is related to the ºA/F sensorº.
CIRCUIT DESCRIPTION
Refer to DTC P2195 on page 05-269.
DTC No.DTC Detection ConditionTrouble Area
P2238
A/F sensor (bank 1 sensor 1) circuit low
A/F sensor admittance is less than 0.022 1/W
(1 trip detection logic)HINT:
Main trouble area

Open in A/F sensor circuit
P2238

Condition (a) continues for 5.0 seconds or more :
(a) AF+ is 0.5 V or less

Condition (a) continues for 5.0 seconds or more :
(a) (AF+) - (AF-) is 0.1 V or less
(1 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

ECM
P2239A/F sensor (bank 1 sensor 1) circuit high
(1 trip detection logic)HINT:
Main trouble area

Short in A/F sensor circuit
P2239

Condition (a) continues for 5.0 seconds or more :
(a) AF+ is more than 4.5 V

Condition (a) continues for 5.0 seconds or more :
(a) (AF+) - (AF-) is more than 0.8 V
(1 trip detection logic)

Same as DTC No. P2238
P2252
Condition (a) continues for 5.0 seconds or more :
(a) AF- is 0.5 V or less
(1 trip detection logic)

Same as DTC No. P2238
P2253
Condition (a) continues for 5.0 seconds or more :
(a) AF- is more than 4.5 V
(1 trip detection logic)

Same as DTC No. P2238
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MONITOR DESCRIPTION
The air-fuel ratio (A/F) sensor varies its voltage output in proportion to the air-fuel ratio. If impedance (alter-
nating current resistance) or voltage output of the sensor deviates greatly from the standard, the ECM deter-
mines that an open or short is in the A/F sensor circuit.
MONITOR STRATEGY
Related DTCs
P2238: A/F sensor (Bank1) open circuit between AF+ and AF-
P2238: A/F sensor (Bank1) short circuit between AF+ and AF-
P2238: A/F sensor (Bank 1) short circuit between AF+ and GND
P2239: A/F sensor (Bank 1) short circuit between AF+ and +B
P2252: A/F sensor (Bank 1) short circuit between AF- and GND
P2253: A/F sensor (Bank 1) short circuit between AF- and +B
Required sensors/ components (Main)A/F sensor
Required sensors/ components (Related)ECT sensor, CKP sensor
Frequency of operationOnce per driving cycle
Duration10 sec.
MIL operation2 driving cycles
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
All:
The monitor will run whenever these DTCs are not presentSee page 05-16
P2238 (open circuit between AF+ and AF-):
Duration while all of the following conditions are met:20 seconds or more
AF+ terminal voltage0.5 to 4.5 V
AF- terminal voltage0.5 to 4.5 V
Difference between AF+ terminal and AF- terminal voltages0.1 to 0.8 V
ECT20C (68F) or more
Engine conditionRunning
Time after engine start20 seconds or more
Fuel-cutOFF
A/F sensor heater duty cycle0.5% or more
Time after A/F sensor heating20 seconds or more
Battery voltage10.5 V or more
Ignition switchON
Others:
Battery voltage10.5 V or more
Ignition switchON

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TYPICAL MALFUNCTION THRESHOLDS
P2238 (Open circuit between AF+ and AF-):
A/F sensor admittanceBelow 0.022 1/ohm
P2238 (Short circuit between AF+ and GND):
AF+ terminal voltage0.5 V or less
P2238 (Short circuit between AF+ and AF-):
Difference between AF+ terminal and AF- terminal voltages0.1 V or less
P2239 (Short circuit between AF+ and +B):
AF+ terminal voltageMore than 4.5 V
P2252 (Short circuit between AF- and GND):
AF- terminal voltage0.5 V or less
P2253 (Short circuit between AF- and +B):
AF- terminal voltageMore than 4.5 V
WIRING DIAGRAM
Refer to DTC P2195 on page 05-269.
INSPECTION PROCEDURE
HINT:
Hand-held tester only:
The malfunctioning area can be found by the ACTIVE TEST A/F CONTROL operation. The A/F CONTROL
operation can determine if the A/F sensor, heated oxygen sensor or other suspected trouble areas are mal-
functioning or not.
(a) Perform the ACTIVE TEST A/F CONTROL operation.
HINT:
The A/F CONTROL operation lowers the injection volume by 12.5 % or increases the injection volume by
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 idling (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

+25 %
-12.5 %
More than 3.35 V
Less than 3.0 V
Case 1
Case 2
Case 3
Case 4
Output voltage of A/F sensor
(sensor 1)
Injection volume
Output voltage
Output voltage of heated oxygen
sensor (sensor 2)Main suspect
trouble area
OK
+25 %
-12.5 %
More than 3.35 V
Less than 3.0V
Injection volume
Output voltage
+25 %
-12.5 %
More than 0.55 V
Less than 0.4V
Injection volume
Output voltage
A/F sensor
(A/F sensor, heater, A/F sen-
sor circuit)
+25 %
-12.5 %
More than 0.55 V
Less than 0.4V
Injection volume
Output voltage
+25 %
-12.5 %
Injection volume
Output voltage
NG
+25 %
-12.5 %
Injection volume
Output voltage
NG
+25 %
-12.5 %
Injection volume
Output voltage
NG
+25 %
-12.5 %
Injection volume
Output voltage
NGExtremely rich or lean actual
air-fuel ratio
(Injector, fuel pressure, gas
leakage in exhaust system,
etc.) OK
OK
OK
Almost
No reaction
Almost
No reaction
Almost
No reaction Almost
No reaction
'
Heated oxygen sensor
(heated oxygen sensor,
heater, heated oxygen sensor
circuit)
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NOTICE:
The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about
20 seconds of delay at maximum.
The following A/F CONTROL procedure enables a technician to check and graph the voltage outputs of both
the A/F sensor and the heated oxygen sensor.
For displaying the graph, enter ºACTIVE TEST / A/F CONTROL / USER DATAº, select ºAFS B1S1 and O2S
B1S2º by pressing ºYESº and push ºENTERº. Then press ºF4º.
HINT:

If DTC P2237, P2238, P2239, P2251, P2252 or P2253 is displayed, check the bank 1 sensor 1 circuit.

Read freeze frame data using the hand-held tester or the OBD II scan tool. 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, and other data from the time the malfunction occurred.