Nissan Pathfinder (2005 year). Instruction — part 210
DTC P1278, P1288 A/F SENSOR 1
EC-531
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2005 Pathfinder
DTC P1278, P1288 A/F SENSOR 1
PFP:22693
Component Description
UBS00KF2
The air fuel ratio (A/F) sensor 1 is a planar dual-cell limit current sen-
sor. The sensor element of the air fuel ratio (A/F) sensor 1 is the
combination of a Nernst concentration cell (sensor cell) with an oxy-
gen-pump cell, which transports ions. It has a heater in the element.
The sensor is capable of precise measurement
= 1, but also in the
lean and rich range. Together with its control electronics, the sensor
outputs a clear, continuous signal throughout a wide
range (0.7 <
< air).
The exhaust gas components diffuse through the diffusion gap at the
electrode of the oxygen pump and Nernst concentration cell, where
they are brought to thermodynamic balance.
An electronic circuit controls the pump current through the oxygen-
pump cell so that the composition of the exhaust gas in the diffusion
gap remains constant at
= 1. Therefore, the air fuel ratio (A/F) sen-
sor 1 is able to indicate air/fuel ratio by this pumping of current. In
addition, a heater is integrated in the sensor to ensure the required
operating temperature of 700 - 800
°
C (1,292 - 1,472
°
F).
CONSULT-II Reference Value in Data Monitor Mode
UBS00KF3
Specification data are reference values.
On Board Diagnosis Logic
UBS00KF4
To judge the malfunction of air fuel ratio (A/F) sensor 1, this diagnosis measures response time of the A/F sig-
nal computed by ECM from the air fuel ratio (A/F) sensor 1 signal. The time is compensated by engine operat-
ing (speed and load), fuel feedback control constant, and the air fuel ratio (A/F) sensor 1 temperature index.
Judgment is based on whether the compensated time (the A/F signal cycling time index) is inordinately long or
not.
SEF579Z
SEF580Z
MONITOR ITEM
CONDITION
SPECIFICATION
A/F SEN1 (B1)
A/F SEN1 (B2)
●
Engine: After warming up
Maintaining engine speed at
2,000 rpm
Fluctuates around 1.5V
DTC No.
Trouble diagnosis name
DTC detecting condition
Possible Cause
P1278
1278
(Bank 1)
Air fuel ratio (A/F) sensor 1
circuit slow response
●
The response (from RICH to LEAN) of the A/F
signal computed by ECM from air fuel ratio (A/
F) sensor 1 signal takes more than the speci-
fied time.
●
Harness or connectors
(The air fuel ratio (A/F) sensor 1 cir-
cuit is open or shorted.)
●
Air fuel ratio (A/F) sensor 1
●
Air fuel ratio (A/F) sensor 1 heater
●
Fuel pressure
●
Fuel injector
●
Intake air leaks
●
Exhaust gas leaks
●
PCV
●
Mass air flow sensor
P1288
1288
(Bank 2)
EC-532
DTC P1278, P1288 A/F SENSOR 1
2005 Pathfinder
DTC Confirmation Procedure
UBS00KF5
NOTE:
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 10 seconds before conducting the next test.
TESTING CONDITION:
Before performing the following procedure, confirm that battery voltage is more than 11V at idle.
WITH CONSULT-II
1.
Start engine and warm it up to normal operating temperature.
2.
Turn ignition switch OFF and wait at least 10 seconds.
3.
Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1minute under no load.
4.
Let engine idle for 1 minute.
5.
Select “A/F SEN1(B1) P1278/P1279” or “A/F SEN1(B1) P1288/P1289” of “A/F SEN1” in “DTC WORK
SUPPORT” mode with CONSULT-II.
6.
Touch “START”.
If “COMPLETED” appears on CONSULT-II screen, go to step
10.
If “COMPLETED” does not appear on CONSULT-II screen, go to
the following step.
7.
After perform the following procedure, “TESTING” will be dis-
played on the CONSULT-II screen.
a.
Increase the engine speed up to 4,000 to 5,000 rpm and keep it
for 10 seconds.
b.
Fully release accelerator pedal and then let engine idle for about
10 seconds.
If “TESTING” is not displayed after 10 seconds, refer to
148, "TROUBLE DIAGNOSIS - SPECIFICATION VALUE"
.
8.
Wait for about 20 seconds at idle at under the condition that
“TESTING” is displayed on the CONSULT-II screen.
9.
Make sure that “TESTING” changes to “COMPLETED”.
If “TESTING” changed to “OUT OF CONDITION”, refer to
EC-148, "TROUBLE DIAGNOSIS - SPECIFICATION VALUE"
.
10. Make sure that “OK” is displayed after touching “SELF-DIAG
RESULT”.
If “NG” is displayed, go to
EC-537, "Diagnostic Procedure"
.
WITH GST
1.
Start engine and warm it up to normal operating temperature.
2.
Select Service $01 with GST.
3.
Calculate the total value of “Short term fuel trim” and “Long term fuel trim” indications.
Make sure that the total percentage should be within
±
15%.
If OK, go to the following step.
If NG, check the following.
PBIB0756E
PBIB1925E
PBIB0758E
DTC P1278, P1288 A/F SENSOR 1
EC-533
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2005 Pathfinder
●
Intake air leaks
●
Exhaust gas leaks
●
Incorrect fuel pressure
●
Lack of fuel
●
Fuel injector
●
Incorrect PCV hose connection
●
PCV valve
●
Mass air flow sensor
4.
Turn ignition switch OFF and wait at least 10 seconds.
5.
Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1minute under no load.
6.
Let engine idle for 1 minute.
7.
Increase the engine speed up to 4,000 to 5,000 rpm and keep it for 10 seconds.
8.
Fully release accelerator pedal and then let engine idle for about 1 minute.
9.
Repeat steps from 4 to 8.
10. Select Service $03 with GST and make sure that no DTC is displayed.
If the DTC is displayed, go to
EC-537, "Diagnostic Procedure"
.
EC-534
DTC P1278, P1288 A/F SENSOR 1
2005 Pathfinder
Wiring Diagram
UBS00KF6
BANK 1
BBWA1730E
DTC P1278, P1288 A/F SENSOR 1
EC-535
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2005 Pathfinder
Specification data are reference values and are measured between each terminal and ground.
CAUTION:
Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
TER-
MINAL
NO.
WIRE
COLOR
ITEM
CONDITION
DATA (DC Voltage)
16
BR
A/F sensor 1 (Bank 1)
[Engine is running]
●
Warm-up condition
●
Idle speed
Approximately 3.1V
35
O
Approximately 2.6V
56
LG
Approximately 2.3V
75
P
Approximately 2.3V
EC-536
DTC P1278, P1288 A/F SENSOR 1
2005 Pathfinder
BANK 2
BBWA1731E
DTC P1278, P1288 A/F SENSOR 1
EC-537
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2005 Pathfinder
Specification data are reference values and are measured between each terminal and ground.
CAUTION:
Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
Diagnostic Procedure
UBS00KF7
1.
CHECK GROUND CONNECTIONS
1.
Turn ignition switch OFF.
2.
Loosen and retighten three ground screws on the body. Refer to
.
OK or NG
OK
>> GO TO 2.
NG
>> Repair or replace ground connections.
2.
RETIGHTEN AIR FUEL RATIO (A/F) SENSOR 1
Loosen and retighten the air fuel ratio (A/F) sensor 1.
>> GO TO 3.
TER-
MINAL
NO.
WIRE
COLOR
ITEM
CONDITION
DATA (DC Voltage)
57
GR
A/F sensor 1 (Bank 2)
[Engine is running]
●
Warm-up condition
●
Idle speed
Approximately 2.6V
58
O
Approximately 2.3V
76
V
Approximately 3.1V
77
Y
Approximately 2.3V
BBIA0539E
Tightening torque: 50 N-m (5.1 kg-m, 37 ft-lb)
BBIA0557E
EC-538
DTC P1278, P1288 A/F SENSOR 1
2005 Pathfinder
3.
CHECK EXHAUST GAS LEAK
1.
Start engine and run it at idle.
2.
Listen for an exhaust gas leak before three way catalyst (manifold).
OK or NG
OK
>> GO TO 4.
NG
>> Repair or replace.
4.
CHECK FOR INTAKE AIR LEAK
Listen for an intake air leak after the mass air flow sensor.
OK or NG
OK
>> GO TO 5.
NG
>> Repair or replace.
PBIB1216E
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