2001 TOYOTA HIGHLANDER o2 sensor

05-134
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
324 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
TYPICAL ENABLING CONDITIONS
The monitor will run whenever these DTCs are not presentSee page 05-16
Fuel system statusClosed Loop
Battery voltage11 V or more
Throttle position learningCompleted
Either of the following conditions is met:Condition 1 or 2
1. Engine RPMLess than 1,100 rpm
2. Intake air amount per revolution0.22 g/rev or more
TYPICAL MALFUNCTION THRESHOLDS
Purge-cutExcecuting
Either of the following conditions is met:Condition 1 or 2
1. Average between short-term fuel trim and long-term fuel
trim34% or more (varies with ECT)
2. Average between short-term fuel trim and long-term fuel
trim-34% or less (varies with ECT)
WIRING DIAGRAM
Refer to DTC P2195 on page 05-269.
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 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)
05-135
325 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:

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.

A high A/F sensor voltage could be caused by a RICH air fuel mixture. Check the conditions that might
cause the engine to run with a RICH air fuel mixture.

A low A/F sensor voltage could be caused by a LEAN air fuel mixture. Check the conditions that might
cause the engine to run with a LEAN air fuel mixture.

S01196S01699
30
20
10
5
3
02040 0.11
0.3
0.2 0.52
60 80 100 -20
(-4) (104) (140) (176)(32) (68) (212)
A81700
Ohmmeter
Acceptable
Temperature C (F)
Resistance kW
05-138
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
328 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
5 INSPECT ENGINE COOLANT TEMPERATURE SENSOR (RESISTANCE)
(a) Remove the ECT sensor.
(b) Measure the resistance of the ECT sensor terminals.
Standard:
Tester ConnectionConditionSpecified Condition
1 - 220C (68F)2.32 to 2.59 kW
1 - 280C (176F)0.310 to 0.326 kW
NOTICE:
When checking the ECT sensor in water, be careful not to
allow water to go into the terminals. After the check, dry the
sensor.
HINT:
Alternate procedure: Connect an ohmmeter to the installed
ECT sensor and read the resistance. Use an infrared thermom-
eter to measure the engine temperature in the immediate vicin-
ity of the sensor. Compare these values to the resistance/tem-
perature graph. Change the engine temperature (warm up or
allow to cool down) and repeat the test.
NG REPLACE ENGINE COOLANT TEMPERATURE
SENSOR
OK
6 CHECK FOR SPARK AND IGNITION (See page 18-1)
OK: Spark occurs.
NG REPAIR OR REPLACE
OK
7 CHECK FUEL PRESSURE (See page 11-4)
(a) Check the fuel pressure (high or low pressure).
Standard:
ItemSpecified Condition
Fuel pressure304 to 343 kPa (3.1 to 3.5 kgf/cm2, 44 to 55 psi)
NG REPLACE FUEL SYSTEM
OK

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
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-139
329 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
8 CHECK FOR EXHAUST GAS LEAKS
OK: No gas leak.
NG REPAIR OR REPLACE EXHAUST GAS
LEAKAGE POINT (See page 15-2)
OK
9 READ VALUE OF HAND-HELD TESTER OR OBD II SCAN TOOL (OUTPUT
VOLTAGE OF AIR FUEL RATIO SENSOR (BANK 1 SENSOR 1))
(a) Connect the hand-held tester or the OBD II scan tool to the DLC3.
(b) Warm up the A/F sensor (bank 1 sensor 1) by running the engine at 2,500 rpm for approximately 90
seconds.
(c) Read A/F sensor voltage output on the hand-held tester or the OBD II scan tool.
(d) Hand-held tester only:
Enter the following menus: ENHANCED OBD II / SNAPSHOT / MANUAL SNAPSHOT / USER DATA.
(e) Select ºAFS B1 S1 / ENGINE SPDº and press YES.
(f) Monitor the A/F sensor voltage carefully.
(g) Check the A/F sensor voltage output under the following conditions:
(1) Allow the engine to idle for 30 seconds.
(2) Running the engine at approximately 2,500 rpm (where engine RPM is not suddenly changed).
(3) Raise the engine speed to 4,000 rpm and quickly release the accelerator pedal so that the throttle
is fully closed.
Standard:
Condition (1) and (2)
Voltage change of 3.3 V (0.66 V)* (between approximately 3.1 to 3.5 V), as shown in the illustra-
tion.
Condition (3)
A/F sensor voltage increases to 3.8 V (0.76 V)* or more when fuel is cut during engine decelera-
tion, as shown in the illustration.
*: Voltage when using the OBD II scan tool.

A52607
AF-AF+
A6
A/F sensor
05-140
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
330 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
HINT:

Whenever the output voltage of the A/F sensor remains at approximately 3.3 V (0.660 V)* (see ºMal-
function 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 output voltage of the A/F sensor 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 cut) during engine deceleration. This will cause a LEAN condition
and should result in a momentary increase in A/F sensor voltage output.

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:
You may notice that the output voltage of the A/F sensor is below 2.8 V (0.76 V)* during fuel enrich-
ment. For example, when the vehicle tries to overtake another vehicle on a highway, the vehicle speed
is suddenly increased with the accelerator pedal fully depressed. The A/F sensor is functioning normal-
ly.

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 17
NG
10 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

A90346
A/F Sensor
Heater
Sensor
A1A+ HA1A
Duty
Control ECM
From
Battery
EFI NO. 1
Fuse
A1A-
MREL EFI Relay
+B
AF-
AF+ HT
EFI NO. 2
Fuse Reference (Bank 1 Sensor 1 System Drawing)
12
34
Y
A76787
A81695A85512
Wire Harness Side
A6
A/F Sensor
+B
AF- HT
AF+
E8
ECM
A1A+
A1A-
HA1A
05-142
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
332 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
12 CHECK WIRE HARNESS (A/F SENSOR - ECM)
(a) Disconnect the A6 A/F sensor connector.
(b) Disconnect the E8 ECM connector.
(c) Measure the resistance of the wire harness side connec-
tors.
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 E8-23 (A1A+) - Body ground
A6-4 (AF-) or E8-31 (A1A-) - Body ground
A6-1 (HT) or E8-5 (HA1A) - Body ground
10 kW or higher
NG REPAIR OR REPLACE HARNESS AND
CONNECTOR
OK
13 REPLACE AIR FUEL RATIO SENSOR
GO

05-144
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
334 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
16 CONFIRM IF 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 (DTCS P0171, P0172)
17 PERFORM CONFIRMATION DRIVING PATTERN
HINT:
Clear all DTCs prior to performing the confirmation driving pattern (refer to step 14).
GO
18 READ OUTPUT DTC (DTC P0171, P0172 ARE OUTPUT AGAIN)
(a) Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
Display (DTC Output)Proceed to
DTC P0171, P0172 are output againA
DTC P0171, P0172 are not output againB
B Go to step 22
A
19 REPLACE AIR FUEL RATIO SENSOR
GO
20 PERFORM CONFIRMATION DRIVING PATTERN
HINT:
Clear all DTCs prior to performing the confirmation driving pattern (refer to step 14).
GO

05-146
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
336 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0300 RANDOM/MULTIPLE CYLINDER MISFIRE
DETECTED
DTC P0301 CYLINDER 1 MISFIRE DETECTED
DTC P0302 CYLINDER 2 MISFIRE DETECTED
DTC P0303 CYLINDER 3 MISFIRE DETECTED
DTC P0304 CYLINDER 4 MISFIRE DETECTED
CIRCUIT DESCRIPTION
When a misfire occurs in the engine, hydrocarbons (HC) are output in high concentrations. If this HC con-
centration is high enough, there could be an increase in exhaust emission levels. High concentrations of HC
can also cause the temperature of the catalyst to increase, possibly damaging the catalyst. To prevent in-
creases in emissions and limit the possibility of thermal damage, the ECM monitors the misfire rate. When
the temperature of the catalyst reaches a point of thermal degradation, the ECM will blink the MIL. For moni-
toring misfires, the ECM uses both the camshaft position sensor and the crankshaft position sensor. The
camshaft position sensor is used to identify misfiring cylinders and the crankshaft position sensor is used
to measure variations in the crankshaft rotation speed. A misfire is counted when crankshaft rotation speed
variations exceed threshold values.
If the misfiring rate exceeds the threshold value and could cause emission deterioration, the ECM illuminates
the MIL.
05ETT-05