2004 INFINITI QX56 engine

POWER SUPPLY AND GROUND CIRCUIT
EC-129
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Revision: August 20072004 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 ProcedureUBS00H0G
1. INSPECTION START
Start engine.
Is engine running?
Ye s o r N o
Yes >> GO TO 9.
No >> GO TO 2.
2. CHECK 10A FUSE
1. Turn ignition switch OFF.
2. Check 10A fuse (No. 59, located in the fuse and relay box).
OK or NG
OK >> Reinstall fuse. GO TO 3.
NG >>

Repair harness or connectors

Replace fuse
3. CHECK ECM POWER SUPPLY CIRCUIT-I
1. Turn ignition switch ON.
2. Check voltage between ECM terminal 109 and ground with
CONSULT-II or tester.
OK or NG
OK >> GO TO 5.
NG >> GO TO 4.
TER-
MINAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
1 B ECM ground[Engine is running]

Idle speedBody ground
109 B/R Ignition switch[Ignition switch: OFF]0V
[Ignition switch: ON]BATTERY VOLTAGE
(11 - 14V)
111 W / BECM relay
(Self shut-off)[Engine is running]
[Ignition switch: OFF]

For a few seconds after turning ignition
switch OFF0 - 1.5V
[Ignition switch: OFF]

More than a few seconds after turning igni-
tion switch OFFBATTERY VOLTAGE
(11 - 14V)
11 5
11 6B
B/WECM ground[Engine is running]

Idle speedBody ground
11 9
120BR
BRPower supply for ECM[Ignition switch: ON]BATTERY VOLTAGE
(11 - 14V)
Voltage: Battery voltage
MBIB0015E

EC-138Revision: August 2007
DTC P0037, P0038, P0057, P0058 HO2S2 HEATER
2004 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-139
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Revision: August 20072004 QX56
DTC Confirmation ProcedureUBS00H0Q
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 between 10.5V and 16V at
idle.
WITH CONSULT-II
1. Turn ignition switch ON and select “DATA MONITOR” mode with CONSULT-II.
2. Start engine and warm it up to the normal operating tempera-
ture.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Start the engine and keep the engine speed between 3,500 rpm
and 4,000 rpm for at least 1 minute under no load.
5. Let engine idle for 1 minute.
6. If 1st trip DTC is detected, go to EC-143, "
Diagnostic Procedure"
.
WITH GST
Follow the procedure “WITH CONSULT-II” above.
SEF 1 74 Y

DTC P0037, P0038, P0057, P0058 HO2S2 HEATER
EC-141
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EC
Revision: August 20072004 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]

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 load.0 - 1.0V
[Ignition switch: ON]

Engine stopped
[Engine is running]

Engine speed is above 3,600 rpm.BATTERY VOLTAGE
(11 - 14V)

DTC P0037, P0038, P0057, P0058 HO2S2 HEATER
EC-143
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Revision: August 20072004 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 HO2S2 POWER SUPPLY CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect heated oxygen sensor 2 harness connector.
3. Turn ignition switch ON.
4. Check voltage between HO2S2 terminal 3 and ground with
CONSULT-II or tester.
OK or NG
OK >> GO TO 3.
NG >> GO TO 2.
TER-
MINAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
25 O/GHeated oxygen sensor 2
heater (bank 2)[Engine is running]

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 load.0 - 1.0V
[Ignition switch: ON]

Engine stopped
[Engine is running]

Engine speed is above 3,600 rpm.BATTERY VOLTAGE
(11 - 14V)
BBIA0435E
Voltage: Battery voltage
PBIB0 112 E

EC-146Revision: August 2007
DTC P0101 MAF SENSOR
2004 QX56
DTC P0101 MAF SENSORPFP:22680
Component DescriptionUBS00H0V
The mass air flow sensor is placed in the stream of intake air. It mea-
sures the intake flow rate by measuring a part of the entire intake
flow. The mass air flow sensor controls the temperature of the hot
wire to a certain amount. The heat generated by the hot wire is
reduced as the intake air flows around it. The more air, the greater
the heat loss.
Therefore, the electric current supplied to the hot wire is changed to
maintain the temperature of the hot wire as air flow increases. The
ECM detects the air flow by means of this current change.
CONSULT-II Reference Value in Data Monitor ModeUBS00H0W
Specification data are reference values.
On Board Diagnosis LogicUBS00H0X
This self-diagnosis has the one trip detection logic.
BBIA0355E
MONITOR ITEM CONDITION SPECIFICATION
MAS A/F SE-B1

Engine: After warming up

Air conditioner switch: OFF

Shift lever: N

No loadIdle Approx. 1.1 - 1.4V
2,500 rpm Approx. 1.7 - 2.0V
CAL/LD VALUE

Engine: After warming up

Air conditioner switch: OFF

Shift lever: N

No loadIdle 14% - 33%
2,500 rpm 12% - 25%
MASS AIRFLOW

Engine: After warming up

Air conditioner switch: OFF

Shift lever: N

No loadIdle 3.0 - 9.0 g·m/s
2,500 rpm 9.0 - 28.0 g·m/s
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0101
0101Mass air flow sensor circuit
range/performance problemA)A high voltage from the sensor is sent to ECM
under light load driving condition.

Harness or connectors
(The sensor circuit is open or
shorted.)

Mass air flow sensor
B)A low voltage from the sensor is sent to ECM
under heavy load driving condition.

Harness or connectors
(The sensor circuit is open or
shorted.)

Intake air leaks

Mass air flow sensor

DTC P0101 MAF SENSOR
EC-147
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Revision: August 20072004 QX56
DTC Confirmation ProcedureUBS00H0Y
Perform PROCEDURE FOR MALFUNCTION A first.
If the DTC cannot be confirmed, perform PROCEDURE FOR MALFUNCTION B.
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.
PROCEDURE FOR MALFUNCTION A
NOTE:
If engine will not start or stops soon, wait at least 10 seconds with engine stopped (Ignition switch ON) instead
of running engine at idle speed.
With CONSULT-II
1. Turn ignition switch ON.
2. Select “DATA MONITOR” mode with CONSULT-II.
3. Start engine and warm it up to normal operating temperature.
4. Run engine for at least 10 seconds at idle speed.
5. If DTC is detected, go to EC-150, "
Diagnostic Procedure" .
With GST
Follow the procedure “With CONSULT-II” above.
PROCEDURE FOR MALFUNCTION B
CAUTION:
Always drive vehicle at a safe speed.
With CONSULT-II
1. Turn ignition switch ON.
2. Start engine and warm it up to normal operating temperature.
If engine cannot be started, go to EC-150, "
Diagnostic Procedure" .
3. Select “DATA MONITOR” mode with CONSULT-II.
4. Check the voltage of “MAS A/F SE-B1” with “DATA MONITOR”.
5. Increases engine speed to about 4,000 rpm.
6. Monitor the linear voltage rise in response to engine speed
increases.
If NG, go to EC-150, "
Diagnostic Procedure" .
If OK, go to following step.
SEF 1 74 Y
SEF 2 43 Y

EC-148Revision: August 2007
DTC P0101 MAF SENSOR
2004 QX56
7. Maintain the following conditions for at least 10 consecutive sec-
onds.
8. If DTC is detected, go to EC-150, "
Diagnostic Procedure" .
Overall Function CheckUBS00H0Z
PROCEDURE FOR MALFUNCTION B
Use this procedure to check the overall function of the mass air flow sensor circuit. During this check, a DTC
might not be confirmed.
With GST
1. Start engine and warm it up to normal operating temperature.
2. Select MODE 1 with GST.
3. Check the mass air flow sensor signal with MODE 1.
4. Check for linear mass air flow sensor signal value rise in
response to increases to about 4,000 rpm in engine speed.
5. If NG, go to EC-150, "
Diagnostic Procedure" .
ENG SPEED More than 2,000 rpm
THRTL SEN 1 More than 3V
THRTL SEN 2 More than 3V
Selector lever Suitable position
Driving locationDriving vehicle uphill (Increased engine load) will help
maintain the driving conditions required for this test.
PBIB0199E
SEF 5 34 P