2004 INFINITI QX56 Air

DTC P1278, P1288 A/F SENSOR 1
EC-479
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Revision: August 20072004 QX56
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

EC-480Revision: August 2007
DTC P1278, P1288 A/F SENSOR 1
2004 QX56
5. CLEAR THE SELF-LEARNING DATA
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Select “SELF-LEARNING CONT” in “WORK SUPPORT” mode with CONSULT-II.
3. Clear the self-learning control coefficient by touching “CLEAR”
or “START”.
4. Run engine for at least 10 minutes at idle speed.
Is the 1st trip DTC P0171, P172, P0174 or P0175 detected?
Is it difficult to start engine?
Without CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF.
3. Disconnect mass air flow sensor harness connector.
4. Restart engine and let it idle for at least 5 seconds.
5. Stop engine and reconnect mass air flow sensor harness con-
nector.
6. Make sure DTC P0102 is displayed.
7. Erase the DTC memory. Refer to EC-62, "
HOW TO ERASE
EMISSION-RELATED DIAGNOSTIC INFORMATION" .
8. Make sure DTC P0000 is displayed.
9. Run engine for at least 10 minutes at idle speed.
Is the 1st trip DTC P0171, P0172, P0174 or P0175 detected?
Is it difficult to start engine?
Ye s o r N o
Yes >> Perform trouble diagnosis for DTC P0171, P0174 or P0172, P0175. Refer to EC-208 or EC-217
.
No >> GO TO 6.
SEF 9 68 Y
BBIA0368E

DTC P1278, P1288 A/F SENSOR 1
EC-481
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Revision: August 20072004 QX56
6. CHECK A/F SENSOR 1 POWER SUPPLY CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect A/F sensor 1 harness connector.
3. Turn ignition switch ON.
4. Check voltage between A/F sensor 1 terminal 3 and ground with
CONSULT-II or tester.
OK or NG
OK >> GO TO 8.
NG >> GO TO 7.
7. DETECT MALFUNCTIONING PART
Check the following.

Harness connectors E5, F14

IPDM E/R harness connector E119

10A fuse

Harness for open or short between A/F sensor 1 and fuse
>> Repair or replace harness or connectors. Voltage: Battery voltage
BBIA0376E
PBIB1683E

EC-482Revision: August 2007
DTC P1278, P1288 A/F SENSOR 1
2004 QX56
8. CHECK A/F SENSOR 1 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Check harness continuity between A/F sensor 1 terminal and ECM terminal as follows.
Refer to Wiring Diagram.
4. Check harness continuity between the following terminals and ground.
Refer to Wiring Diagram.
5. Also check harness for short to power.
OK or NG
OK >> GO TO 9.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.
9. CHECK AIR FUEL RATIO (A/F) SENSOR 1 HEATER
Refer to EC-360, "
Component Inspection" .
OK or NG
OK >> GO TO 10.
NG >> Replace A/F sensor 1.
10. CHECK MASS AIR FLOW SENSOR
Refer to EC-153, "
Component Inspection" .
OK or NG
OK >> GO TO 11.
NG >> Replace mass air flow sensor.
A/F sensor 1 terminal ECM terminal
Bank1116
275
535
656
Bank 2176
277
557
658
Continuity should exist.
Bank 1 Bank 2
A/F sensor 1 terminal ECM terminal A/F sensor 1 terminal ECM terminal
116176
275277
535557
656658
Continuity should not exist.

DTC P1278, P1288 A/F SENSOR 1
EC-483
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Revision: August 20072004 QX56
11 . CHECK PCV VALVE
Refer to EC-645, "
POSITIVE CRANKCASE VENTILATION" .
OK or NG
OK >> GO TO 12.
NG >> Repair or replace PCV valve.
12. CHECK INTERMITTENT INCIDENT
Perform EC-127, "
TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT" .
OK or NG
OK >> Replace A/F sensor 1.
NG >> Repair or replace.
Removal and InstallationUBS00HAL
AIR FUEL RATIO (A/F) SENSOR 1
Refer to EM-19, "EXHAUST MANIFOLD AND THREE WAY CATALYST" .

EC-484Revision: August 2007
DTC P1279, P1289 A/F SENSOR 1
2004 QX56
DTC P1279, P1289 A/F SENSOR 1PFP:22693
Component DescriptionUBS00HAM
The air fuel ratio (A/F) sensor 1 is a planar dual-cell limit current sen-
sor. The sensor element of the A/F sensor 1 is the combination of a
Nernst concentration cell (sensor cell) with an oxygen-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 A/F sensor 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 tempera-
ture of 700 - 800°C (1,292 - 1,472°F).
CONSULT-II Reference Value in Data Monitor ModeUBS00HAN
Specification data are reference values.
On Board Diagnosis LogicUBS00HAO
To judge the malfunction of A/F sensor 1, this diagnosis measures response time of the A/F signal computed
by ECM from the air fuel ration A/F sensor 1 signal. The time is compensated by engine operating (speed and
load), fuel feedback control constant, and the 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.
SEF 5 79 Z
SEF 5 80 Z
MONITOR ITEM CONDITION SPECIFICATION
A/F SEN1 (B1)
A/F SEN1 (B2)

Engine: After warming upMaintaining engine speed at
2,000 rpmFluctuates around 1.5V
DTC No. Trouble diagnosis name DTC detecting condition Possible Cause
P1279
1279
(Bank 1)
Air fuel ratio (A/F) sensor 1
circuit slow response

The response (from LEAN to RICH) of the A/F
signal computed by ECM from A/F sensor 1
signal takes more than the specified time.

Harness or connectors
(The A/F sensor 1 circuit is open or
shorted.)

Air fuel ratio (A/F) sensor 1

Air fuel ratio (A/F) sensor 1 heater

Fuel pressure

Injector

Intake air leaks

Exhaust gas leaks

PCV

Mass air flow sensor P1289
1289
(Bank 2)

EC-486Revision: August 2007
DTC P1279, P1289 A/F SENSOR 1
2004 QX56

Intake air leaks

Exhaust gas leaks

Incorrect fuel pressure

Lack of fuel

Injectors

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. Select “MODE 7” with GST.
If the 1st trip DTC is displayed, go to EC-490, "
Diagnostic Procedure" .

EC-490Revision: August 2007
DTC P1279, P1289 A/F SENSOR 1
2004 QX56
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 ProcedureUBS00HAR
1. CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten three ground screws on the body.
Refer to EC-133, "
Ground Inspection" .
OK or NG
OK >> GO TO 2.
NG >> Repair or replace ground connections.
2. RETIGHTEN A/F SENSOR 1
Loosen and retighten the A/F sensor 1.
>> GO TO 3.
TER-
MINAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
57 L/P
A/F sensor 1 (Bank 2)[Engine is running]

Warm-up condition

Idle speedApproximately 2.6V
58 GR/GApproximately 2.3V
76 G/LApproximately 3.1V
77 BR/BApproximately 2.3V
BBIA0354E
Tightening torque: 50 N-m (5.1 kg-m, 37 ft-lb)
BBIA0375E