2001 TOYOTA SEQUOIA heater

B17393
Engine
RPMEngine
RPM (1) Idling (2) Approximately 2,500 rpm
Fuel Cut
When A/F sensor circuit malfunctioning,
voltage output does not change A/F
Sensor
Voltage A/F
Sensor
Voltage
(1) Idling
Fuel Cut (3) Approximately 4,000 rpm
ºCondition (1), (2)º
Change at approximately 0.66 V Normal Condition:
Malfunction Condition:
ºCondition (3)º
0.76 V or More(1) Idling (2) Approximately 2,500 rpm(3) Approximately 4,000 rpm
(1) Idling
DI±394
± DIAGNOSTICSENGINE
588 Author: Date:
2005 SEQUOIA (RM1146U)
3 Read value output voltage of A/F sensor.
PREPARATION:
(a) Connect the hand±held tester to the DLC3.
(b) Start the engine and turn the scan tool ON.
(c) Warm up the Air±Fuel Ratio (A/F) sensor at an engine speed of 2,500 rpm for 90 seconds.
CHECK:
(a) Using the scan tool, check the A/F sensor voltage 3 times, once when the engine is in each of the fol-
lowing conditions:
(1) While idling (check for at least 30 seconds)
(2) At an engine speed of approximately 2,500 rpm (without any sudden changes in engine speed)
(3) Raise the engine speed to 4,000 rpm and then quickly release the accelerator pedal so that the
throttle valve is fully closed.
Standard:
ConditionsA/F Sensor Voltage VariationsReference
(1) and (2)Changes at approx 0.66 VBetween 0.62 V and 0.7 V
(3)Increases to 0.76 V or moreThis occurs during engine deceleration
(when fuel±cut performed)
For more information, see the diagrams below.
HINT:

If the output voltage of the A/F sensor remains at approximately 0.66 V (see Malfunction Condition
diagram) under any conditions, including those above, the A/F sensor may have an open circuit. (This
will also happen if the A/F sensor heater has an open circuit.)

If the output voltage of the A/F sensor remains at either approximately 0.76 V or more, or 0.56 V or
less (see Malfunction Condition diagram) under any conditions, including those above, the A/F sensor
may have a short circuit.

The ECM stops fuel injection (fuel cut) during engine deceleration. This causes a lean condition and
results in a momentary increase in the A/F sensor output voltage.

B17396
HT +B
AF± AF+ Sensor 1A/F Sensor Component Side:
Front View
A19288
A/F Relay
± DIAGNOSTICSENGINE
DI±397
591 Author: Date:
2005 SEQUOIA (RM1146U)
10 Check resistance of air±fuel ratio (A/F) sensor heater.
PREPARATION:
Disconnect the air±fuel ratio (A/F) sensor connector.
CHECK:
Measure resistance between the terminals of the A/F sensor
connector.
OK:
Tester ConnectionSpecified Condition
HT (1) ± +B (2)Between 1.8 W and 3.4 W at 20C (68F)
HT (1) ± AF± (4)10 kW or higher
NG Replace air±fuel ratio (A/F) sensor.
OK
11 Check A/F relay.
PREPARATION:
Remove the A/F relay from the engine room J/B.
CHECK:
Inspect the A/F relay.
OK:
Standard:
Terminal No.ConditionSpecified Condition
3 ± 5Always10 KW or higher
3 ± 5Apply B+ between
terminals 1 and 2Below 1 W
NG Replace EFI relay.
OK

A23659
Wire Harness Side:
HT
A38
Sensor 1A/F Sensor Connector
AF+
Front ViewAF±
+B A39
B17415A55007
E7ECM Connector
HA1A
A1A+
A1A±
A2A+
A2A±HA2A
A23512
Reference (Bank 1 Sensor 1 System Drawing):
A/F Sensor A/F Relay
Heater
Sensor
A1A+ HA1A
Duty
Control ECM
From
Battery
A/F Heater
Fuse
A1A±
To EFI Relay DI±398
± DIAGNOSTICSENGINE
592 Author: Date:
2005 SEQUOIA (RM1146U)
12 Check for open and short in harness and connector between ECM and A/F sen-
sor.
PREPARATION:
(a) Disconnect the A38 or A39 A/F sensor connector.
(b) Turn the ignition switch to ON.
CHECK:
(a) Measure the voltage between the +B terminal of the A/F
sensor connector and body ground.
Standard:
Tester ConnectionsSpecified Conditions
+B (2) ± Body groundBetween 9 V and 14 V
PREPARATION:
(a) Turn the ignition switch to OFF.
(b) Disconnect the E7 ECM connector.
CHECK:
(a) Check the resistance.
Standard (Check for open):
Tester ConnectionsSpecified Conditions
HT (A38±1) ± HA1A (E7±2)
HT (A39±1) ± HA2A (E7±1)Below 1 W
AF+ (A38±3) ± A1A+ (E7±22)
AF+ (A39±3) ± A2A+ (E7±23)Below 1 W
AF± (A38±4) ± A1A± (E7±30)
AF± (A39±4) ± A2A± (E7±31)Below 1 W
Standard (Check for short):
Tester ConnectionsSpecified Conditions
HT (A38±1) or HA1A (E7±2) ± Body ground
HT (A39±1) or HA2A (E7±1) ± Body ground10 kW or higher
AF+ (A38±3) or A1A+ (E7±22) ± Body ground
AF+ (A39±3) or A2A+ (E7±23) ± Body ground10 kW or higher
AF± (A38±4) or A1A± (E7±30) ± Body ground
AF± (A39±4) or A2A± (E7±31) ± Body ground10 kW or higher

± DIAGNOSTICSENGINE
DI±403
597 Author: Date:
2005 SEQUOIA (RM1146U)
CIRCUIT DESCRIPTION
Refer to DTC P2195 on page DI±383.
DTC No.DTC Detection ConditionsTrouble 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/W
(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
P2242AF+ 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
P2255AF± 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
P2256AF± 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
± DIAGNOSTICSENGINE
598 Author: Date:
2005 SEQUOIA (RM1146U)
MONITOR STRATEGY
A/F sensor (Bank 1) open circuit between AF+
and AF±
P2238A/F sensor (Bank 1) short circuit between AF+
and AF±
A/F sensor (Bank 1) short circuit between AF+
and GND
P2239A/F sensor (Bank 1) short circuit between AF+
and +B
A/F sensor (Bank 2) open circuit between AF+
and AF±
RltdDTC
P2241A/F sensor (Bank 2) short circuit between AF+
and AF±
Related DTCsA/F sensor (Bank 2) short circuit between AF+
and GND
P2242A/F sensor (Bank 2) short circuit between AF+
and +B
P2252A/F sensor (Bank 1) short circuit between AF±
and GND
P2253A/F sensor (Bank 1) short circuit between AF±
and +B
P2255A/F sensor (Bank 2) short circuit between AF±
and GND
P2256A/F sensor (Bank 2) short circuit between AF±
and +B
Required sensors/componentsA/F sensor
Frequency of operationOnce per driving cycle
Duration10 sec.: A/F sensor open circuit between AF+ and AF±
5 sec.: Others
MIL operationImmediate
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
ItSpecificationItemMinimumMaximum
The monitor will run whenever these
DTCs are not presentSee page DI±18
P2238, P2241 (A/F sensor open circuit between AF+ and AF±):
Duration while all of following conditions
met20 sec.±
AF+ terminal voltage0.5 to 4.5 V
AF± terminal voltage0.5 to 4.5 V
Difference between AF+ terminal and AF±
terminal voltage0.1 to 0.8 V
ECT20°C (68°F)±
EngineRunning
Time after engine start20 sec.±
Fuel±cutOFF
A/F sensor heater duty cycle0%±

+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 VoltageMain 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
± DIAGNOSTICSENGINE
600 Author: Date:
2005 SEQUOIA (RM1146U)
Standard:
Tester Display
(Sensor)Injection VolumesStatusVoltages
AFS B1S1 (AFS B2S1)
(A/F)+25 %RichLess than 3.0
AFS B1S1 (AFS B2S1)
(A/F)±12.5 %LeanMore than 3.35
O2S B1S2 (O2S B2S2)
(HO2)+25 %RichMore than 0.55
O2S B1S2 (O2S B2S2)
(HO2)±12.5 %LeanLess 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.

B17396
HT +B
AF± AF+ Sensor 1A/F Sensor Component Side:
Front View
A19288
± DIAGNOSTICSENGINE
DI±407
601 Author: Date:
2005 SEQUOIA (RM1146U)
HINT:
Read freeze frame data using a hand±held tester. Freeze frame data record the engine condition when mal-
functions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was mov-
ing or stationary, 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.
1 Check resistance of air±fuel ratio (A/F) sensor heater.
PREPARATION:
Disconnect the air±fuel ratio (A/F) sensor connector.
CHECK:
Measure resistance between the terminals of the A/F sensor
connector.
OK:
Tester ConnectionSpecified Condition
HT (1) ± +B (2)Between 1.8 W and 3.4 W at 20C (68F)
HT (1) ± AF± (4)10 kW or higher
NG Replace air±fuel ratio (A/F) sensor.
OK
2 Check A/F relay.
PREPARATION:
Remove the A/F relay from the engine room J/B.
CHECK:
Inspect the A/F relay.
OK:
Terminal No.ConditionSpecified Condition
1 ± 2ConstantContinuity
UsuallyNo Continuity
3 ± 5Apply B+ between
terminals 1 and 2Continuity
NG Replace EFI relay.
OK

A23659
Wire Harness Side:
HT
A38
Sensor 1A/F Sensor Connector
AF+
Front ViewAF±
+B A39
B17415A55007
E7ECM Connector
HA1A
A1A+
A1A±
A2A+
A2A±HA2A
A23512
Reference (Bank 1 Sensor 1 System Drawing):
A/F Sensor A/F Relay
Heater
Sensor
A1A+ HA1A
Duty
Control ECM
From
Battery
A/F Heater
Fuse
A1A±
To EFI Relay DI±408
± DIAGNOSTICSENGINE
602 Author: Date:
2005 SEQUOIA (RM1146U)
3 Check for open and short in harness and connector between ECM and A/F sen-
sor.
PREPARATION:
(a) Disconnect the A38 or A39 A/F sensor connector.
(b) Turn the ignition switch to ON.
CHECK:
(a) Measure the voltage between the +B terminal of the A/F
sensor connector and body ground.
OK:
Standard:
Tester ConnectionsSpecified Conditions
+B (2) ± Body groundBetween 9 V and 14 V
PREPARATION:
(a) Turn the ignition switch to OFF.
(b) Disconnect the E7 ECM connector.
CHECK:
(a) Check the resistance.
OK:
Standard (Check for open):
Tester ConnectionsSpecified Conditions
HT (A38±1) ± HA1A (E7±2)
HT (A39±1) ± HA2A (E7±1)Below 1 W
AF+ (A38±3) ± A1A+ (E7±22)
AF+ (A39±3) ± A2A+ (E7±23)Below 1 W
AF± (A38±4) ± A1A± (E7±30)
AF± (A39±4) ± A2A± (E7±31)Below 1 W
Standard (Check for short):
Tester ConnectionsSpecified Conditions
HT (A38±1) or HA1A (E7±2) ± Body ground
HT (A39±1) or HA2A (E7±1) ± Body ground10 kW or higher
AF+ (A38±3) or A1A+ (E7±22) ± Body ground
AF+ (A39±3) or A2A+ (E7±23) ± Body ground10 kW or higher
AF± (A38±4) or A1A± (E7±30) ± Body ground
AF± (A39±4) or A2A± (E7±31) ± Body ground10 kW or higher