Toyota Sequoia (2005). Manual — part 152
–
DIAGNOSTICS
ENGINE
DI–403
597
CIRCUIT DESCRIPTION
Refer to DTC P2195 on page
.
DTC No.
DTC Detection Conditions
Trouble Areas
P2238
P2241
Case 1:
Condition (a) or (b) continues for 5.0 seconds or more
(1 trip detection logic):
(a) AF+ voltage 0.5 V or less
(b) (AF+) – (AF–) = 0.1 V or less
Case 2:
A/F sensor admittance: Less than 0.022 1/
Ω
(1 trip detection logic)
Open or short in A/F sensor (sensor 1) circuit
A/F sensor (sensor 1)
A/F sensor heater
EFI relay
A/F sensor heater and relay circuits
ECM
P2239
P2242
AF+ voltage more than 4.5 V for 5.0 seconds or more
(1 trip detection logic)
Open or short in A/F sensor (sensor 1) circuit
A/F sensor (sensor 1)
A/F sensor heater
EFI relay
A/F sensor heater and relay circuits
ECM
P2252
P2255
AF– voltage 0.5 V or less for 5.0 seconds or more
(1 trip detection logic)
Open or short in A/F sensor (sensor 1) circuit
A/F sensor (sensor 1)
A/F sensor heater
EFI relay
A/F sensor heater and relay circuits
ECM
P2253
P2256
AF– voltage more than 4.5 V for 5.0 seconds or more
(1 trip detection logic)
Open or short in A/F sensor (sensor 1) circuit
A/F sensor (sensor 1)
A/F sensor heater
EFI relay
A/F sensor heater and relay circuits
ECM
MONITOR DESCRIPTION
The Air–Fuel Ratio (A/F) sensor varies its output voltage in proportion to the air–fuel ratio. If the A/F sensor
impedance (alternating current resistance) or voltage output deviates greatly from the standard range, the
ECM determines that there is an open or short malfunction in the A/F sensor circuit.
DI–404
–
DIAGNOSTICS
ENGINE
598
MONITOR STRATEGY
A/F sensor (Bank 1) open circuit between AF+
and AF–
P2238
A/F sensor (Bank 1) short circuit between AF+
and AF–
A/F sensor (Bank 1) short circuit between AF+
and GND
P2239
A/F sensor (Bank 1) short circuit between AF+
and +B
A/F sensor (Bank 2) open circuit between AF+
and AF–
R l t d DTC
P2241
A/F sensor (Bank 2) short circuit between AF+
and AF–
Related DTCs
A/F sensor (Bank 2) short circuit between AF+
and GND
P2242
A/F sensor (Bank 2) 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
P2255
A/F sensor (Bank 2) short circuit between AF–
and GND
P2256
A/F sensor (Bank 2) short circuit between AF–
and +B
Required sensors/components
A/F sensor
Frequency of operation
Once per driving cycle
Duration
10 sec.: A/F sensor open circuit between AF+ and AF–
5 sec.: Others
MIL operation
Immediate
Sequence of operation
None
TYPICAL ENABLING CONDITIONS
It
Specification
Item
Minimum
Maximum
The monitor will run whenever these
DTCs are not present
See page
P2238, P2241 (A/F sensor open circuit between AF+ and AF–):
Duration while all of following conditions
met
20 sec.
–
AF+ terminal voltage
0.5 to 4.5 V
AF– terminal voltage
0.5 to 4.5 V
Difference between AF+ terminal and AF–
terminal voltage
0.1 to 0.8 V
ECT
20
°
C (68
°
F)
–
Engine
Running
Time after engine start
20 sec.
–
Fuel–cut
OFF
A/F sensor heater duty cycle
0%
–
–
DIAGNOSTICS
ENGINE
DI–405
599
Time after A/F sensor heating
20 sec.
–
Battery voltage
10.5 V
–
Ignition switch
ON
Others:
Battery voltage
10.5 V
–
Ignition switch
ON
TYPICAL MALFUNCTION THRESHOLDS
Detection Criteria
Threshold
P2238, P2241 (A/F sensor open circuit between AF+ and AF–):
A/F sensor admittance
Bellow 0.022 1/ohm
P2238, P2241 (A/F sensor short circuit between AF+ and GND):
A/F+ terminal voltage
0.5 V or less
P2238, P2241 (A/F sensor short circuit between AF+ and AF–):
Difference between A/F+ terminal and AF– terminal voltage
0.1 V or less
P2239, P2242 (A/F sensor short circuit between AF+ and +B):
A/F+ terminal voltage
More than 4.5 V
P2252, P2255 (A/F sensor short circuit between AF– and GND):
A/F– terminal voltage
0.5 V or less
P2253, P225+ (A/F sensor short circuit between AF– and +B):
A/F– terminal voltage
More than 4.5 V
WIRING DIAGRAM
Refer to DTC P2195 on page
.
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.
+25 %
–12.5 %
More than 3.35 V
Less than 3.0 V
1
A/F Sensor (Sensor 1)
Output Voltage
Injection volume
Output voltage
HO2 Sensor (Sensor 2)
Output Voltage
Main Suspected
Trouble Areas
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
+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
NG
OK
OK
OK
Almost
no reaction
Almost
no reaction
Almost
no reaction
Almost
no reaction
Case
2
3
4
A/F sensor circuit
A/F sensor heater
HO2 sensor
HO2 sensor circuit
HO2 sensor heater
(Air–fuel ratio extremely
lean or rich)
Injector
Gas leakage from
exhaust system
Fuel pressure
DI–406
–
DIAGNOSTICS
ENGINE
600
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
NOTICE:
The Air–Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2)
sensor has a maximum output delay of approximately 20 seconds.
Following the A/F CONTROL procedure enables technicians to check and graph the voltage outputs
of both the A/F and HO2 sensors.
To display the graph, select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD
II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2, and press the YES but-
ton and then the ENTER button followed by the F4 button.
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