check engine TOYOTA SEQUOIA 2001 Service Owners Manual

± DIAGNOSTICSENGINE
DI±157
351 Author: Date:
2005 SEQUOIA (RM1146U)
1 Read output DTC.
PREPARATION:
(a) Connect the hand±held tester to the DLC3.
(b) Turn the ignition switch ON and push the hand±held tester main switch ON.
(c) When using hand±held tester, enter the following menu: DIAGNOSIS / ENHANCED OBD II / DTC
INFO / CURRENT CODES.
CHECK:
Read the DTC using the hand±held tester.
RESULT:
Display (DTC Output)Proceed to
P0138, P0158A
P0137, P0157B
P0136, P0156C
HINT:
If any other codes besides P0136, P0137, P0138, P0156, P0157 and/or P0158 are output, perform the trou-
bleshooting for those DTCs first.
B Go to step 14.
C Go to step 7.
A
2 Check output voltage of heated oxygen sensor.
PREPARATION:
(a) Connect the hand±held tester to the DLC3.
(b) After warming up the engine, run the engine at 2,500 rpm for 3 minutes.
(c) When using hand±held tester, enter the following menu: DIAGNOSIS / ENHANCED OBD II / DATA
LIST / ALL / O2S B1S2 or B2S2.
(d) Allow the engine to idle.
CHECK:
Read the Heated Oxygen (HO2) sensor output voltage while idling.
RESULT:
HO2 Sensor Output VoltagesProceed To
More than 1.2 VA
Less than 1.0 VB
B Go to step 5.
A

B17416HT1BECM Connector
E7OX1B E8
HT2B
OX2B
A21341
+B
OX E1HT
H2
H4
Components Side:
Bank 1 Sensor 2, Bank 2 Sensor 2
DI±158
± DIAGNOSTICSENGINE
352 Author: Date:
2005 SEQUOIA (RM1146U)
3 Check for short in harness and connector between terminal OX1B and HT1B,
OX2B and HT2B of ECM.
PREPARATION:
(a) Turn the ignition switch to OFF and wait for 5 minutes.
(b) Disconnect the E7 and E8 ECM connector.
CHECK:
(a) Check the resistance.
OK:
Standard:
Tester ConnectionsSpecified Conditions
HT1B (E8±1) ± OX1B (E8±18)10 kW or higher
HT2B (E7±5) ± OX2B (E5±33)10 kW or higher
OK Replace ECM (See page SF±80
NG
4 Check resistance of heated oxygen sensor heater.
PREPARATION:
Disconnect the heated oxygen sensor connector.
CHECK:
Measure resistance between terminals of the heated oxygen
sensor.
OK:
Standard:
Tester ConnectionSpecified Condition
HT (1) ± +B (2)11 to 16 W at 20°C (68°F)
+B (2) ± OX (3)10 kW or higher
NG Replace heated oxygen sensor.
OK
Repair or replace harness or connector.
5 Perform confirmation driving pattern.
NEXT

± DIAGNOSTICSENGINE
DI±159
353 Author: Date:
2005 SEQUOIA (RM1146U)
6 Check whether DTC output recurs (DTC P0138, P0158)
CHECK:
(a) On the hand±held tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC
INFO / CURRENT CODES.
(b) Read DTCs.
RESULT:
Display (DTC Output)Proceed To
P0138 or P0158A
No outputB
B Check for intermittent problems
(See page DI±11).
A
Replace heated oxygen sensor.
7 Check output voltage of heated oxygen sensor.
PREPARATION:
(a) Connect the hand±held tester to the DLC3.
(b) Turn the ignition switch to ON and turn the tester ON.
(c) Start the engine.
(d) Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / O2S B1S2.
(e) After warming up the engine, run the engine at an engine speed of 2,500 rpm for 3 minutes.
CHECK:
(a) Read the output voltage of the HO2 sensor when the engine rpm is suddenly increased.
HINT:
Quickly accelerate the engine to 4,000 rpm 3 times using the accelerator pedal.
Standard: Fluctuates between 0.4 V or less and 0.5 V or more.
NG Go to step 14.
OK
8 Perform confirmation driving pattern.
NEXT

DI±160
± DIAGNOSTICSENGINE
354 Author: Date:
2005 SEQUOIA (RM1146U)
9 Check whether DTC output recurs (DTC P0136, P0156)
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
P0136 or P0156A
No outputB
B Check for intermittent problems
(See page DI±11).
A
10 Replace heated oxygen sensor.
NEXT
11 Perform confirmation driving pattern.
NEXT
12 Check whether DTC output recurs (DTC P0136, P0156)
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
P0136 or P0156A
No outputB
B Repair completed.
A

B17391
+12 %
Normal Malfunction±12 %
0 V 3.3 V
1 VA/F Sensor Output
HO2 Sensor OutputInjection Volume
Malfunction
± DIAGNOSTICSENGINE
DI±161
355 Author: Date:
2005 SEQUOIA (RM1146U)
13 Perform active test (injection volume).
PREPARATION:
(a) Connect the hand±held tester to the DLC3.
(b) Start the engine and turn the tester ON.
(c) Warm up the engine.
(d) Select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / INJ VOL.
CHECK:
(a) Change the fuel injection volume using the tester, monitoring the voltage output of Air±Fuel Ratio (A/F)
and HO2 sensors displayed on the tester.
HINT:

Change the fuel injection volume within the range of ±12 % and +12 %. The injection volume can be
changed in 1 % graduations within the range.

The A/F sensor is displayed as AFS B1S1 (AFS B2S1), and the HO2 sensor is displayed as O2S B1S2
(O2S B2S2), on hand±held testers.
RESULT:
Tester Display (Sensor)Voltage VariationsProceed To
AFS B1S1 (AFS B2S1) (A/F)Alternates between more and less than 3.3 VOK
AFS B1S1 (AFS B2S1) (A/F)Remains at more than 3.3 VNG
AFS B1S1 (AFS B2S1) (A/F)Remains at less than 3.3 VNG
HINT:
A normal HO2 sensor voltage (O2S B1S2 (O2S B2S2)) reacts in accordance with increases and decreases
in fuel injection volumes. When the A/F sensor voltage remains at either less or more than 3.3 V despite the
HO2 sensor indicating a normal reaction, the A/F sensor is malfunctioning.
NG Replace air±fuel ratio (A/F) sensor.
OK

A21341
+B
OX E1HT
H2
H4
Components Side:
Bank 1 Sensor 2, Bank 2 Sensor 2
DI±162
± DIAGNOSTICSENGINE
356 Author: Date:
2005 SEQUOIA (RM1146U)
check and repair extremely rich or lean actu-
arial air fuel ratio (injector, fuel pressure, gas
leakages from exhaust system, etc.)
14 Check for exhaust gas leakage.
CHECK:
Check for exhaust gas leakage from the exhaust manifold and pipe.
OK:
No exhaust gas leakage.
NG Repair or replace exhaust gas leakage point.
OK
15 Inspect heated oxygen sensor.
PREPARATION:
Disconnect the HO2 sensor connector.
CHECK:
Measure the resistance between the terminals of the HO2 sen-
sor connector.
OK:
Standard:
Tester ConnectionsSpecified Conditions
HT (2) ± +B (1)11 to 16 W at 20C (68F)
HT (2) ± E (3)10 kW or higher
NG Replace heated oxygen sensor.
OK

A19288
EFI Relay
± DIAGNOSTICSENGINE
DI±163
357 Author: Date:
2005 SEQUOIA (RM1146U)
16 Check EFI relay.
PREPARATION:
Remove the EFI relay from the engine room J/B.
CHECK:
Inspect the EFI 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

A23543
+B
OXR2
OXL2E1 HTR2
HTL2
H2
H4
Wire Harness Side:
Bank 1 Sensor 2, Bank 2 Sensor 2
B17416HT1BECM Connector E7OX1B E8
HT2B
OX2B
A21040
Reference (Bank 1 Sensor 1 System Drawing)
From
BatteryEFI No. 1 FuseEFI Relay
EFI No. 2 FuseHeater Oxygen
Sensor
Heater
SensorHT1A
OX1A
E2
MRELECM
DI±164
± DIAGNOSTICSENGINE
358 Author: Date:
2005 SEQUOIA (RM1146U)
17 Check for open and short in harness and connector between ECM and heated
oxygen sensor.
PREPARATION:
(a) Disconnect the heated oxygen sensor connector.
(b) Disconnect the E7 and E8 ECM connector.
CHECK:
Measure the resistance between the wire harness side connec-
tors.
OK:
Standard:
Tester ConnectionSpecified Condition
OXL2 (H2±3) ± OX1B (E8±18)Below 1 W
HTL2 (H2±1) ± HT1B (E8±1)Below 1 W
OXR2 (H4±3) ± OX2B (E7±33)Below 1 W
HTR2 (H4±1) ± HT2B (E7±5)Below 1 W
OXL2 (H2±3) or OX1B (E8±18) ±
Body ground10 kW or higher
HTL2 (H2±1) or HT1B (E8±1) ±
Body ground10 kW or higher
OXR2 (H4±3) or OX2B (E7±33) ±
Body ground10 kW or higher
HTR2 (H4±1) or HT2B (E7±5) ±
Body ground10 kW or higher
NG Repair or replace harness or connector.
OK
Replace heated oxygen sensor.

+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
± DIAGNOSTICSENGINE
DI±169
363 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.

DI±170
± DIAGNOSTICSENGINE
364 Author: Date:
2005 SEQUOIA (RM1146U)
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.
1 Check any other DTCs output (in addition to DTC P0171, P0172, P0174 or P0175).
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
P0171, P0172, P0174 or P0175A
P0171, P0172, P0174 or P0175 and other DTCsB
HINT:
If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.
B Go to DTC chart (See page DI±58).
A
2 Check connection of PCV piping.
OK:
PCV hose is connected correctly and is not damaged.
NG Repair or replace PCV piping.
OK