2001 TOYOTA SEQUOIA O2 sensor

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.

± DIAGNOSTICSENGINE
DI±395
589 Author: Date:
2005 SEQUOIA (RM1146U)

The ECM must establish a closed throttle valve position learning value to perform fuel cut. If the battery
terminal has been reconnected, the vehicle must be driven over 10 mph (16 km/h) to allow the ECM
to learn the closed throttle valve position.

When the vehicle is driven:
The output voltage of the A/F sensor may be below 0.56 V during fuel enrichment. For the vehicle, this
translates to a sudden increase in speed with the accelerator pedal fully depressed when trying to over-
take another vehicle. The A/F sensor is functioning normally.

The A/F sensor is a current output element; therefore, the current is converted into a voltage inside
the ECM. Measuring the voltage at the connectors of the A/F sensor or ECM will show a constant volt-
age result.
NG Go to step 9.
OK
4 Perform confirmation driving pattern.
NEXT
5 Check whether DTC output recurs (DTC P2195, P2196, P2197 or P2198)
CHECK:
(a) On the hand±held tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC
INFO / PENDING CODES.
(b) Read DTCs.
RESULT:
Display (DTC Output)Proceed To
P2195, P2196, P2197 or P2198A
No outputB
B Go to step 5.
A

DI±396
± DIAGNOSTICSENGINE
590 Author: Date:
2005 SEQUOIA (RM1146U)
6 Replace air fuel ratio sensor.
NEXT
7 Perform confirmation driving pattern.
NEXT
8 Check whether DTC output recurs (DTC P2195, P2196, P2197 or P2198)
CHECK:
(a) On the hand±held tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC
INFO / PENDING CODES.
(b) Read DTCs.
RESULT:
Display (DTC Output)Proceed To
P2195, P2196, P2197 or P2198A
No outputB
B Go to step 5.
A
9 Confirm whether vehicle has run out of fuel in past.
NO Check for intermittent problems
(See page DI±11).
YES
DTC caused by running out of fuel.

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

DI±400
± DIAGNOSTICSENGINE
594 Author: Date:
2005 SEQUOIA (RM1146U)
16 Replace air fuel ratio sensor.
NEXT
17 Perform confirmation driving pattern.
NEXT
18 Check whether DTC output recurs (DTC P2195, P2196, P2197 or P2198)
CHECK:
(a) On the hand±held tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC
INFO / PENDING CODES.
(b) Read DTCs.
RESULT:
Display (DTC Output)Proceed To
P2195, P2196, P2197 or P2198A
No outputB
B Replace ECM (See page SF±80) and perform
confirmation driving pattern.
A
19 Confirm whether vehicle has run out of fuel in past.
NO Check for intermittent problems
(See page DI±11).
YES
DTC caused by running out of fuel.

± DIAGNOSTICSENGINE
DI±401
595 Author: Date:
2005 SEQUOIA (RM1146U)
20 Replace air fuel ratio sensor.
NEXT
21 Perform confirmation driving pattern.
NEXT
22 Check whether DTC output recurs (DTC P2195, P2196, P2197 or P2198)
CHECK:
(a) On the hand±held tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC
INFO / PENDING CODES.
(b) Read DTCs.
RESULT:
Display (DTC Output)Proceed To
P2195, P2196, P2197 or P2198 (A/F sensor pending DTCs)A
No outputB
B Replace ECM (See page SF±80).
A
END

DI±402
± DIAGNOSTICSENGINE
596 Author: Date:
2005 SEQUOIA (RM1146U)
DTC P2238 Oxygen Sensor Pumping Current Circuit
Low (For A/F Sensor)(Bank 1 Sensor1)
DTC P2239 Oxygen Sensor Pumping Current Circuit
High (For A/F Sensor)(Bank 1 Sensor1)
DTC P2241 Oxygen Sensor Pumping Current Circuit
Low (For A/F Sensor)(Bank 2 Sensor1)
DTC P2242 Oxygen Sensor Pumping Current Circuit
High (For A/F Sensor)(Bank 2 Sensor1)
DTC P2252 Oxygen Sensor Reference Ground Circuit
Low (For A/F Sensor)(Bank 1 Sensor1)
DTC P2253 Oxygen Sensor Reference Ground Circuit
High (For A/F Sensor)(Bank 1 Sensor1)
DTC P2255 Oxygen Sensor Reference Ground Circuit
Low (For A/F Sensor)(Bank 2 Sensor1)
DTC P2256 Oxygen Sensor Reference Ground Circuit
High (For A/F Sensor)(Bank 2 Sensor1)
HINT:

Although the DTC titles say oxygen sensor, these DTCs relate to the Air±Fuel Ratio (A/F) sensor.

Sensor 1 refers to the sensor mounted in front of the Three±Way Catalytic Converter (TWC) and lo-
cated near the engine assembly.
DIDFU±01