2005 INFINITI QX4 sensor

TROUBLE DIAGNOSIS - SPECIFICATION VALUE
EC-151
C
D
E
F
G
H
I
J
K
L
MA
EC
Revision: October 20052005 QX56
10. DETECT MALFUNCTIONING PART
1. Check the following.
–Ignition coil and its circuit (Refer to EC-619, "IGNITION SIGNAL" .)
–Fuel injector and its circuit (Refer to EC-631, "INJECTOR CIRCUIT" .)
–Intake air leakage
–Low compression pressure (Refer to EM-58, "CHECKING COMPRESSION PRESSURE" .)
2. If NG, repair or replace the malfunctioning part.
If OK, replace fuel injector. (It may be caused by leakage from fuel injector or clogging.)
>> GO TO 11.
11 . CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”
1. Start engine.
2. Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “DATA MONITOR (SPEC)” mode, and make sure that the
each indication is within the SP value.
OK or NG
OK >>INSPECTION END
NG >> GO TO 12.
12. CHECK A/F SENSOR 1 FUNCTION
Perform all DTC Confirmation Procedure related with A/F sensor 1.

For DTC P1271, P1281, refer to EC-459, "DTC Confirmation Procedure" .

For DTC P1272, P1282, refer to EC-468, "DTC Confirmation Procedure" .

For DTC P1273, P1283, refer to EC-477, "DTC Confirmation Procedure" .

For DTC P1274, P1284, refer to EC-487, "DTC Confirmation Procedure" .

For DTC P1276, P1286, refer to EC-497, "DTC Confirmation Procedure" .

For DTC P1278, P1288, refer to EC-508, "DTC Confirmation Procedure" .

For DTC P1279, P1289, refer to EC-520, "DTC Confirmation Procedure" .
OK or NG
OK >> GO TO 15.
NG >> GO TO 13.
13. CHECK A/F SENSOR 1 CIRCUIT
Perform Diagnostic Procedure according to corresponding DTC.
>> GO TO 14.
14. CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”
1. Start engine.
2. Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “DATA MONITOR (SPEC)” mode, and make sure that the
each indication is within the SP value.
OK or NG
OK >>INSPECTION END
NG >> GO TO 15.

EC-152Revision: October 2005
TROUBLE DIAGNOSIS - SPECIFICATION VALUE
2005 QX56
15. DISCONNECT AND RECONNECT ECM HARNESS CONNECTOR
1. Stop the engine.
2. Disconnect ECM harness connector. Check pin terminal and connector for damage, and then reconnect it.
>> GO TO 16.
16. CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”
1. Start engine.
2. Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “DATA MONITOR (SPEC)” mode, and make sure that the
each indication is within the SP value.
OK or NG
OK >>INSPECTION END
NG >> Detect malfunctioning part according to EC-104, "
Symptom Matrix Chart" .
17. CHECK “B/FUEL SCHDL”
Select “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and
make sure that the indication is within the SP value.
OK or NG
OK >>INSPECTION END
NG (More than the SP value)>>GO TO 18.
NG (Less than the SP value)>>GO TO 25.
18. DETECT MALFUNCTIONING PART
1. Check for the cause of large engine friction. Refer to the following.
–Engine oil level is too high
–Engine oil viscosity
–Belt tension of power steering, alternator, A/C compressor, etc. is excessive
–Noise from engine
–Noise from transmission, etc.
2. Check for the cause of insufficient combustion. Refer to the following.
–Valve clearance malfunction
–Intake valve timing control function malfunction
–Camshaft sprocket installation malfunction, etc.
>> Repair or replace malfunctioning part, and then GO TO 30.
19. CHECK INTAKE SYSTEM
Check for the cause of uneven air flow through mass air flow sensor. Refer to the following.

Crushed air ducts

Malfunctioning seal of air cleaner element

Uneven dirt of air cleaner element

Improper specification of intake air system
OK or NG
OK >> GO TO 21.
NG >> Repair or replace malfunctioning part, and then GO TO 20.
PBIB2332E

TROUBLE DIAGNOSIS - SPECIFICATION VALUE
EC-153
C
D
E
F
G
H
I
J
K
L
MA
EC
Revision: October 20052005 QX56
20. CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”, AND “B/FUEL SCHDL”
Select “A/F ALPHA-B1”, “A/F ALPHA-B2”, and “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and
make sure that the each indication is within the SP value.
OK or NG
OK >>INSPECTION END
NG (“B/FUEL SCHDL” is more, “A/F ALPHA-B1”, “A/F ALPHA-B2” are less than the SP value)>>GO TO 21.
21. DISCONNECT AND RECONNECT MASS AIR FLOW SENSOR HARNESS CONNECTOR
1. Stop the engine.
2. Disconnect mass air flow sensor harness connector. Check pin terminal and connector for damage and
then reconnect it again.
>> GO TO 22.
22. CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”
1. Start engine.
2. Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “DATA MONITOR (SPEC)” mode, and make sure that the
each indication is within the SP value.
OK or NG
OK >> 1. Detect malfunctioning part of mass air flow sensor circuit and repair it. Refer to EC-183, "DTC
P0102, P0103 MAF SENSOR" .
2. GO TO 29.
NG >> GO TO 23.
23. CHECK “MAS A/F SE-B1”
Select “MAS A/F SE-B1” in “DATA MONITOR (SPEC)” mode, and
make sure that the indication is within the SP value.
OK or NG
OK >> GO TO 24.
NG (More than the SP value)>>Replace mass air flow sensor, and
then GO TO 29.
24. REPLACE ECM
1. Replace ECM.
2. Perform initialization of NVIS(NATS) system and registration of all NVIS(NATS) ignition key IDs. Refer to
BL-139, "
ECM Re-communicating Function" .
3. Perform EC-90, "
VIN Registration" .
4. Perform EC-90, "
Accelerator Pedal Released Position Learning" .
5. Perform EC-90, "
Throttle Valve Closed Position Learning" .
6. Perform EC-91, "
Idle Air Volume Learning" .
>> GO TO 29.
PBIB2370E

EC-154Revision: October 2005
TROUBLE DIAGNOSIS - SPECIFICATION VALUE
2005 QX56
25. CHECK INTAKE SYSTEM
Check for the cause of uneven air flow through mass air flow sensor. Refer to the following.

Crushed air ducts

Malfunctioning seal of air cleaner element

Uneven dirt of air cleaner element

Improper specification of intake air system
OK or NG
OK >> GO TO 27.
NG >> Repair or replace malfunctioning part, and then GO TO 26.
26. CHECK “B/FUEL SCHDL”
Select “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and make sure that the indication is within the
SP value.
OK or NG
OK >>INSPECTION END
NG (Less than the SP value)>>GO TO 27.
27. CHECK “MAS A/F SE-B1”
Select “MAS A/F SE-B1” in “DATA MONITOR (SPEC)” mode, and
make sure that the indication is within the SP value.
OK or NG
OK >> GO TO 28.
NG (Less than the SP value)>>Replace mass air flow sensor, and
then GO TO 30.
28. CHECK INTAKE SYSTEM
Check for the cause of air leak after the mass air flow sensor. Refer to the following.

Disconnection, looseness, and cracks in air duct

Looseness of oil filler cap

Disconnection of oil level gauge

Open stuck, breakage, hose disconnection, or cracks of PCV valve

Disconnection or cracks of EVAP purge hose, open stuck of EVAP canister purge volume control solenoid
valve

Malfunctioning seal of rocker cover gasket

Disconnection, looseness, or cracks of hoses, such as vacuum hose, connecting to intake air system
parts

Malfunctioning seal of intake air system, etc.
>> GO TO 30.
29. CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”, AND “B/FUEL SCHDL”
Select “A/F ALPHA-B1”, “A/F ALPHA-B2”, and “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and
make sure that the each indication is within the SP value.
OK or NG
OK >>INSPECTION END
NG >> Detect malfunctioning part according to EC-104, "
Symptom Matrix Chart" .
PBIB2370E

EC-166Revision: October 2005
DTC P0037, P0038, P0057, P0058 HO2S2 HEATER
2005 QX56
DTC P0037, P0038, P0057, P0058 HO2S2 HEATERPFP:226A0
DescriptionUBS00H0N
SYSTEM DESCRIPTION
The ECM performs ON/OFF control of the heated oxygen sensor 2 heater corresponding to the engine speed,
amount of intake air and engine coolant temperature.
OPERATION
CONSULT-II Reference Value in Data Monitor ModeUBS00H0O
Specification data are reference values.
On Board Diagnosis LogicUBS00H0P
Sensor Input signal to ECM ECM function Actuator
Camshaft position sensor (PHASE)
Crankshaft position sensor (POS)Engine speed
Heated oxygen sensor 2
heater controlHeated oxygen sensor 2 heater
Engine coolant temperature sensor Engine coolant temperature
Mass air flow sensor Amount of intake air
Engine speed rpm Heated oxygen sensor 2 heater
Above 3,600OFF
Below 3,600 rpm after the following conditions are met.

Engine: After warming up

Keeping the engine speed between 3,500 and 4,000 rpm for 1
minute and at idle for 1 minute under no loadON
MONITOR ITEM CONDITION SPECIFICATION
HO2S2 HTR (B1)
HO2S2 HTR (B2)

Engine speed is below 3,600 rpm after the following conditions are met.
–Engine: After warming up
–Keeping the engine speed between 3,500 and 4,000 rpm for 1 minute and
at idle for 1 minute under no loadON

Engine speed: Above 3,600 rpm OFF
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0037
0037
(Bank 1)
Heated oxygen sensor 2
heater control circuit lowThe current amperage in the heated oxygen sen-
sor 2 heater circuit is out of the normal range.
(An excessively low voltage signal is sent to ECM
through the heated oxygen sensor 2 heater.)

Harness or connectors
(The heated oxygen sensor 2 heater
circuit is open or shorted.)

Heater oxygen sensor 2 heater P0057
0057
(Bank 2)
P0038
0038
(Bank 1)
Heated oxygen sensor 2
heater control circuit highThe current amperage in the heated oxygen sen-
sor 2 heater circuit is out of the normal range.
(An excessively high voltage signal is sent to
ECM through the heated oxygen sensor 2
heater.)

Harness or connectors
(The heated oxygen sensor 2 heater
circuit is shorted.)

Heater oxygen sensor 2 heater P0058
0058
(Bank 2)

DTC P0037, P0038, P0057, P0058 HO2S2 HEATER
EC-169
C
D
E
F
G
H
I
J
K
L
MA
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.
TER-
MINAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
6GRHeated oxygen sensor 2
heater (bank 1)[Engine is running]

Warm-up condition

Engine speed is below 3,600 rpm after the
following conditions are met.
–Keeping the engine speed between 3,500
and 4,000 rpm for 1 minute and at idle for 1
minute under no load.0 - 1.0V
[Ignition switch: ON]

Engine: Stopped
[Engine is running]

Engine speed: Above 3,600 rpm.BATTERY VOLTAGE
(11 - 14V)

DTC P0037, P0038, P0057, P0058 HO2S2 HEATER
EC-171
C
D
E
F
G
H
I
J
K
L
MA
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 ProcedureUBS00H0S
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)
25 O/GHeated oxygen sensor 2
heater (bank 2)[Engine is running]

Warm-up condition

Engine speed is below 3,600 rpm after the
following conditions are met.
–Keeping the engine speed between 3,500
and 4,000 rpm for 1 minute and at idle for 1
minute under no load.0 - 1.0V
[Ignition switch: ON]

Engine: Stopped
[Engine is running]

Engine speed: Above 3,600 rpm.BATTERY VOLTAGE
(11 - 14V)
BBIA0354E

EC-172Revision: October 2005
DTC P0037, P0038, P0057, P0058 HO2S2 HEATER
2005 QX56
2. CHECK HO2S2 POWER SUPPLY CIRCUIT
1. Disconnect heated oxygen sensor 2 harness connector.
2. Turn ignition switch ON.
3. Check voltage between HO2S2 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 connector E119

10A fuse

Harness for open or short between heated oxygen sensor 2 and fuse
>> Repair harness or connectors.
4. CHECK HO2S2 OUTPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Check harness continuity between ECM terminal and HO2S2 terminal as follows.
Refer to Wiring Diagram.
4. Also check harness for short to ground and 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.
BBIA0435E
Voltage: Battery voltage
PBIB0 112 E
DTCTe r m i n a l s
Bank
ECM Sensor
P0037, P0038 6 2 1
P0057, P0058 25 2 2
Continuity should exist.