2001 TOYOTA HIGHLANDER o2 sensor

05-282
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
472 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
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
05EVY-06

- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-283
473 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
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

05-284
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
474 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
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)
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-285
475 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
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.

A52607
AF-AF+
A6
A/F sensor
B60778
5
12 312
5
3
05-286
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
476 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
1 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
2 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
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-287
477 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
3 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
REPLACE ECM (See page 10-9)

A96746
Fuel Tank Canister
Vacuum Pump: OFF Pressure Sensor 0.02 Inch Orifice
Pump Module
Operation A: Atmospheric Pressure Measurement
Vent Valve: OFF (vent)
Operation D: Purge VSV monitor Operation B, E: 0.02 Inch Leak Pressure Measurement
Negative
Pressure Atmospheric
Pressure Air Filter
Purge VSV: OFFOFF (vent)
ON
OFF
OFF
ON
ON (closed)ON
ON
ON (closed)
Operation C: EVAP System Pressure Measurement
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)(From August, 2004)
05-289
479 Author
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MONITOR DESCRIPTION
5 hours* after the ignition switch is turned OFF, the electric vacuum pump creates negative pressure (vacu-
um) in the EVAP (Evaporative Emission) system. The ECM monitors for leaks and actuator malfunctions
based on the EVAP pressure.
HINT:
*: If the engine coolant temperature is not below 35C (95F) 5 hours after the ignition switch is turned off,
the monitor check starts 2 hours later. If it is still not below 35C (95F) 7 hours after the ignition switch is
turned off, the monitor check starts 2.5 hours later.
SequenceOperationsDescriptionsDuration
-ECM activationActivated by soak timer, 5 hours (7 or 9.5 hours) after ignition switch turned to OFF.-
AAtmospheric pressure
measurement
Vent valve turned OFF (vent) and EVAP system pressure measured by ECM in order to
register atmospheric pressure.
If EVAP pressure is not between 70 kPa and 110 kPa (525 mmHg and 825 mmHg), ECM
cancels EVAP system monitor.
10 seconds
B
First 0.02 inch leak
pressure measure-
mentIn order to determine 0.02 inch leak pressure standard, vacuum pump creates negative pres-
sure (vacuum) through 0.02 inch orifice and them ECM checks if vacuum pump and vent
valve operate normally.
60 seconds
CEVAP system pres-
sure measurement
Vent valve turned ON (closed) to shut EVAP system.
Negative pressure (vacuum) created in EVAP system, and EVAP system pressure then
measured.
Write down the measured value as it will be used in the leak check.
If EVAP pressure does not stabilize within 15 minutes, ECM cancels EVAP system monitor.
15 minutes*
DPurge VSV monitorPurge VSV opened and then EVAP system pressure measured by ECM.
Large increase indicates normal.10 seconds
E
Second 0.02 inch leak
pressure measure-
mentLeak check is performed after second 0.02 inch leak pressure standard is measured.
If stabilized system pressure higher than second 0.02 inch leak pressure standard, ECM
determines that EVAP system leaking.
60 seconds
FFinal checkAtmospheric pressure measured and then monitoring result recorded by ECM.-
* If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

- DIAGNOSTICSSFI SYSTEM (2AZ-FE)(From August, 2004)
05-291
481 Author
: Date
:
OBD II MONITOR SPECIFICATIONS
Monitor Strategy
Required Sensors/ComponentsPurge VSV and pump module
Frequency of OperationOnce per driving cycle
DurationWithin 15 minutes (varies with amount of fuel in tank)
MIL Operation2 driving cycles
Sequence of OperationNone
Typical Enabling Conditions
The monitor will run whenever these DTCs are not presentSee page 05-16
EVAP key-off monitor runs when all of the following condi-
tions are met:-
Atomspheric pressure525 to 825 mmHg (70 to 110 kPa)
Battery voltage10.5 V or more
Vehicle speedBelow 4 km/h (2.5 mph)
Ignition switchOFF
Engine conditionNot running
Time after engine is stopped5 hours
FTP sensor malfunction (P0450, P0452, P0453)Not detected
Purge VSVNot operated by scan tool
Vent valveNot operated by scan tool
Leak detection pumpNot operated by scan tool
Both of the following conditions are met before IG switch
OFF:Condition 1 and 2
1. Duration that vehicle is driven5 min. or more
2. Purge flowExecuted
ECT4.4 to 35C (40 to 95F)
IAT4.4 to 35C (40 to 95F)
Example of re-start time
First time7 hours
Second time9 hours and 30 min.
Key-of f monitor sequence: 1 to 8
1. Atmospheric pressure
Next sequence is run if following condition met-
Atmospheric pressure change for 10 sec.Within 2.25 mmHg (0.3 kPa) for 1 sec.
2. First reference pressure
Next sequence is run if all of following conditions metCondition 1, 2 and 3
1. FTP when 4 sec. after reference pressure measurement-7.5 mmHg (-1 kPa) or less
2. Reference pressure-36.47 to -7.93 mmHg (-4.85 to -1.057 kPa)
3. Reference pressureSaturated
3. Vent valve stuck closed check
Next sequence is run if following condition met-
FTP change for 10 sec. after vent valve ON (closed)2.25 mmHg (0.3 kPa) or more
4. Vacuum introduction and leak
Next sequence is run if both of following conditions metCondition 1 and 2
1. Vacuum introduction timeWithin 15 min.
2. FTPFTP was saturated
5. Purge VSV stuck closed check
Next sequence is run if following condition met-
FTP change for 10 sec. after purge VSV ON (open)2.25 mmHg (0.3 kPa) or more