2001 TOYOTA SEQUOIA fuel

+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±392
± DIAGNOSTICSENGINE
586 Author: Date:
2005 SEQUOIA (RM1146U)
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.
HINT:

Read freeze frame data using a hand±held tester. Freeze frame data record the engine condition when
malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle
was moving 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.

A low A/F sensor voltage could be caused by a rich air±fuel mixture. Check for conditions that would
cause the engine to run rich.

A high A/F sensor voltage could be caused by a lean air±fuel mixture. Check for conditions that would
cause the engine to run lean.

± DIAGNOSTICSENGINE
DI±393
587 Author: Date:
2005 SEQUOIA (RM1146U)
1 Check any other DTCs output (in addition to DTC P2195, P2196, P2197 or P2198).
PREPARATION:
(a) Connect a hand±held tester to the DLC3.
(b) Turn the ignition switch to ON and turn the tester ON.
(c) Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
CHECK:
(a) Read DTCs.
Result:
Display (DTC Output)Proceed To
P2195, P2196, P2197 or P2198A
P2195, P2196, P2197 or P2198 and other DTCsB
HINT:
If any DTCs other than P2195, P2196, P2197 or P2198 are output, troubleshoot those DTCs first.
B Go to DTC chart (See page DI±58).
A
2 Check A/F sensor output current.
PREPARATION:
(a) Connect a hand±held tester to the DLC3.
(b) Turn the ignition switch to ON and turn the tester ON.
(c) Clear DTCs (see page DI±43).
(d) On the hand±held tester, select the following menu items: DIAGNOSIS/ENHANCED OBD II/MON-
ITOR INFO/MONITOR STATUS.
(e) Check that the status of O2S MON is COMPL.
(f) On the hand±held tester, select the following menu items: DIAGNOSIS/ENHANCED OBD II/MON-
ITOR INFO/TEST RESULT/RANGE BISI and B2S1.
(g) Check the test value of the air±fuel ratio sensor output current during fuel±cut.
RESULT:
Test ValueProceed to
Out of normal range (1.4 mA or more, and less than 3.6 mA)A
Within normal range (Less than 1.4 mA, or 3.6 mA or more)B
B Go to step 20.
A

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

± DIAGNOSTICSENGINE
DI±399
593 Author: Date:
2005 SEQUOIA (RM1146U)
NG Replace or replace harness or connector.
OK
13 Check air induction system (See page SF±1).
CHECK:
Check the air induction system for vacuum leaks.
NG Repair or replace air induction system.
OK
14 Check fuel pressure (See page SF±7).
CHECK:
Check the fuel pressure (high or low pressure).
NG Check and replace fuel pump, pressure regula-
tor, fuel pipe line and filter (See page SF±1).
OK
15 Check injector injection (See page SF±29).
NG Replace injector.
OK

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.