2005 INFINITI QX4 ignition

DTC P1276, P1286 A/F SENSOR 1
EC-503
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Revision: October 20052005 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 ProcedureUBS00HAD
1. CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten three ground screws on the body.
Refer to EC-162, "
Ground Inspection" .
OK or NG
OK >> GO TO 2.
NG >> Repair or replace ground connections.
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

EC-504Revision: October 2005
DTC P1276, P1286 A/F SENSOR 1
2005 QX56
2. CHECK AIR FUEL RATIO (A/F) SENSOR 1 POWER SUPPLY CIRCUIT
1. Disconnect A/F sensor 1 harness connector.
2. Turn ignition switch ON.
3. Check voltage between A/F sensor 1 terminal 3 and ground with
CONSULT-II or tester.
OK or NG
OK >> GO TO 4.
NG >> GO TO 3.
3. 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

DTC P1276, P1286 A/F SENSOR 1
EC-505
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Revision: October 20052005 QX56
4. 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 5.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.
5. CHECK INTERMITTENT INCIDENT
Perform EC-156, "
TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT" .
OK or NG
OK >> GO TO 6.
NG >> Repair or replace.
6. REPLACE AIR FUEL RATIO (A/F) SENSOR 1
Replace air fuel ratio (A/F) sensor 1.
CAUTION:

Discard any air fuel ratio (A/F) sensor which has been dropped from a height of more than 0.5 m
(19.7 in) onto a hard surface such as a concrete floor; use a new one.

Before installing new air fuel ratio (A/F) sensor, clean exhaust system threads (using Oxygen Sen-
sor Thread Cleaner tool J-43897-18 or J-43897-12) and approved anti-seize lubricant.
>>INSPECTION END
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.

EC-508Revision: October 2005
DTC P1278, P1288 A/F SENSOR 1
2005 QX56
DTC Confirmation ProcedureUBS00HAI
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 EC-
146, "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-146, "
TROUBLE DIAGNOSIS - SPECIFICATION VALUE" .
10. Make sure that “OK” is displayed after touching “SELF-DIAG
RESULT”.
If “NG” is displayed, go to EC-513, "
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-509
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Revision: October 20052005 QX56

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. Select Service $07 with GST.
If the 1st trip DTC is displayed, go to EC-513, "
Diagnostic Procedure" .

DTC P1278, P1288 A/F SENSOR 1
EC-513
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EC
Revision: October 20052005 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 ProcedureUBS00HAK
1. CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten three ground screws on the body.
Refer to EC-162, "
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: 40 - 60 N-m (4.1 - 6.1 kg-m, 30 - 44 ft-lb)
BBIA0375E

DTC P1278, P1288 A/F SENSOR 1
EC-515
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Revision: October 20052005 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-236, "DTC
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION" or EC-245, "DTC P0172, P0175 FUEL
INJECTION SYSTEM FUNCTION" .
No >> GO TO 6.
SEF 9 68 Y
BBIA0368E

EC-516Revision: October 2005
DTC P1278, P1288 A/F SENSOR 1
2005 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