Toyota Sequoia (2005). Manual — part 164
A23458
Air–fuel Ratio Sensor Output:
Active A/F Control
A/F Sensor Output
Fuel Injection Volume
ON
OFF
Normal
Malfunction
10 Seconds
–
DIAGNOSTICS
ENGINE
DI–451
645
DTC
P2A00
A/F Sensor Circuit Slow Response (Bank 1
Sensor 1)
DTC
P2A03
A/F Sensor Circuit Slow Response (Bank 2
Sensor 1)
CIRCUIT DESCRIPTION
Refer to DTC P2195 on page
.
DTC No.
DTC Detection Conditions
Trouble Areas
P2A00
P2A03
Calculated test value for A/F sensor response rate deteriora-
tion level is less than threshold.
Open or short in A/F sensor (sensor 1) circuit
A/F sensor (sensor 1)
ECM
MONITOR DESCRIPTION
After engine is warmed up, the ECM performs air–fuel ratio feedback control to regulate the air–fuel ratio
at stoichiometric ratio. In addition, this vehicle performs Active A/F Ratio Control for approximately 10 se-
conds after preconditions met in order to measure the A/F sensor response rate. During active air–fuel ratio
control, the ECM forcibly increases and decreases the injection volume for certain amount based on learned
stoichiomentric air –fuel ratio during usual air–fuel feedback control, and measures the A/F sensor response
rate. The ECM calculates the signal from the A/F sensor while value for A/F sensor response rate deteriora-
tion level.
If the test value for A/F sensor response rate deterioration level is less than threshold, ECM interprets this
as a malfunction, and sets the DTC.
DIDFY–01
Vehicle speed
(40 –120 km/h)
25 – 75mph)
(g)
(h)
Warm up
3 minutes
DI–452
–
DIAGNOSTICS
ENGINE
646
CONFIRMATION DRIVING PATTERN
(a)
Connect the hand–held tester to the DLC3.
(b)
Turn the ignition switch to ON.
(c)
Turn the hand–held tester ON.
(d)
Clear DTCs.
(e)
Select the following menu items: DIAGNOSIS/ENHANCED OBD II/MONITOR INFO/MONITOR RE-
SULT.
(f)
Check that RES RATE B1 S1 is INCOMPL.
(g)
Start the engine and warm it up.
(h)
Drive the vehicle at between 25 mph and 75 mph (40 km/h and 120km/h) for 3 minutes. However, the
vehicle should be driven at constant–speed.
(i)
When detection is complete, Response rate of MONITOR RESULT changes.
If the value does not change, perform step (g) once more.
(j)
Notes the value of the Monitor Result.
(k)
Select the following menu items: DIAGNOSIS/ENHANCED OBD II/DTC INFO/ PENDING CODES.
(l)
Check if any DTCs (any pending DTCs) are set.
MONITOR STRATEGY
R l t d DTC
P2A00
A/F sensor (Bank 1) slow response
Related DTCs
P2A03
A/F sensor (Bank 2) slow response
Required sensors/components
A/F sensor
Frequency of operation
Once per driving cycle
Duration
10 to 15 sec.
MIL operation
2 driving cycles
Sequence of operation
None
–
DIAGNOSTICS
ENGINE
DI–453
647
TYPICAL ENABLING CONDITIONS
It
Specification
Item
Minimum
Maximum
The monitor will run whenever these
DTCs are not present
See page
Battery voltage
11 V
–
ECT
75
°
C (167
°
F)
–
Idle
OFF
Engine RPM
–
4,000 rpm
A/F sensor status
Activated
Fuel cut
OFF
Engine load
10 to 70%
Estimated catalyst temperature
500 to 800
°
C (932 to 1,472
°
F)
Shift position
2nd
–
Catalyst monitor
Not executing
Intake air amount
2.5 to 12 g/sec
TYPICAL MALFUNCTION THRESHOLDS
Detection Criteria
Threshold
Response rate deterioration level
Less than 0.2 V
Number of average
5 or more
MONITOR RESULT
Refer to page
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 ”Confirmation Monitor”).
MID (Monitor Identification Data) is assigned to each emissions–related component.
TID (Test Identification Data) is assigned to each test value.
Scaling is used to calculate the test value indicated on generic OBD ll scan tools.
A/F sensor bank 1 sensor 1
MID
TID
Scaling
Description of Test Value
Minimum Test Limit
Maximum Test Limit
$01
$8E
Multiply by 0.0003
(no dimension)
Response rate deterioration level for
A/F sensor
Malfunction criterion
FF
A/F sensor bank 2 sensor 1
MID
TID
Scaling
Description of Test Value
Minimum Test Limit
Maximum Test Limit
$05
$8E
Multiply by 0.0003
(no dimension)
Response rate deterioration level for
A/F sensor
Malfunction criterion
FF
WIRING DIAGRAM
Refer to DTC P2195 on page
.
DI–454
–
DIAGNOSTICS
ENGINE
648
INSPECTION PROCEDURE
HINT:
Hand–held tester only:
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 Volumes
Status
Voltages
AFS B1S1 (AFS B2S1)
(A/F)
+25 %
Rich
Less than 3.0
AFS B1S1 (AFS B2S1)
(A/F)
–12.5 %
Lean
More than 3.35
O2S B1S2 (O2S B2S2)
(HO2)
+25 %
Rich
More than 0.55
O2S B1S2 (O2S B2S2)
(HO2)
–12.5 %
Lean
Less than 0.4
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