2005 INFINITI QX4 ignition

DTC P0037, P0038, P0057, P0058 HO2S2 HEATER
EC-171
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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 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.

DTC P0101 MAF SENSOR
EC-175
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Revision: October 20052005 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 1st trip DTC is detected, go to EC-178, "
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-178, "
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-178, "
Diagnostic Procedure" .
If OK, go to following step.
SEF 1 74 Y
SEF 2 43 Y

EC-178Revision: October 2005
DTC P0101 MAF SENSOR
2005 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 ProcedureUBS00H11
1. INSPECTION START
Which malfunction (A or B) is duplicated?
A or B
A >> GO TO 3.
B >> GO TO 2.
2. CHECK INTAKE SYSTEM
Check the following for connection.

Air duct

Vacuum hoses

Intake air passage between air duct to intake manifold
OK or NG
OK >> GO TO 3.
NG >> Reconnect the parts.
TER-
MINAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
51 W Mass air flow sensor[Engine is running]

Warm-up condition

Idle speed1.0 - 1.3V
[Engine is running]

Warm-up condition

Engine speed: 2,500 rpm.1.7 - 2.1V
67 B Sensor ground[Engine is running]

Warm-up condition

Idle speedApproximately 0V
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 9
120BR
BRPower supply for ECM[Ignition switch: ON]BATTERY VOLTAGE
(11 - 14V)

DTC P0101 MAF SENSOR
EC-179
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Revision: October 20052005 QX56
3. 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 4.
NG >> Repair or replace ground connections.
4. CHECK MAF SENSOR POWER SUPPLY CIRCUIT
1. Disconnect mass air flow (MAF) sensor harness connector.
2. Turn ignition switch ON.
3. Check voltage between MAF sensor terminal 2 and ground with
CONSULT-II or tester.
OK or NG
OK >> GO TO 6.
NG >> GO TO 5.
5. DETECT MALFUNCTIONING PART
Check the following.

Harness connectors E2, F32

Harness for open or short between IPDM E/R and mass air flow sensor

Harness for open or short between mass air flow sensor and ECM
>> Repair harness or connectors.
BBIA0354E
BBIA0368E
Voltage: Battery voltage
PBIB11 68 E

EC-180Revision: October 2005
DTC P0101 MAF SENSOR
2005 QX56
6. CHECK MAF SENSOR GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Check harness continuity between MAF sensor terminal 3 and ECM terminal 67.
Refer to Wiring Diagram.
4. Also check harness for short to ground and short to power.
OK or NG
OK >> GO TO 7.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.
7. CHECK MAF SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between MAF sensor terminal 4 and ECM terminal 51.
Refer to Wiring Diagram.
2. Also check harness for short to ground and short to power.
OK or NG
OK >> GO TO 8.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.
8. CHECK INTAKE AIR TEMPERATURE SENSOR
Refer to EC-194, "
Component Inspection" .
OK or NG
OK >> GO TO 9.
NG >> Replace intake air temperature sensor.
9. CHECK EVAP CONTROL SYSTEM PRESSURE SENSOR
Refer to EC-334, "
Component Inspection" .
OK or NG
OK >> GO TO 10.
NG >> Replace EVAP control system pressure sensor.
10. CHECK MASS AIR FLOW SENSOR
Refer to EC-181, "
Component Inspection" .
OK or NG
OK >> GO TO 11.
NG >> Replace mass air flow sensor.
11 . CHECK INTERMITTENT INCIDENT
Refer to EC-156, "
TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT" .
>>INSPECTION END Continuity should exist.
Continuity should exist.

DTC P0101 MAF SENSOR
EC-181
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Revision: October 20052005 QX56
Component InspectionUBS00H12
MASS AIR FLOW SENSOR
With CONSULT-II
1. Reconnect all harness connectors disconnected.
2. Start engine and warm it up to normal operating temperature.
3. Connect CONSULT-II and select “DATA MONITOR” mode.
4. Select “MAS A/F SE-B1” and check indication under the follow-
ing conditions.
*: Check for linear voltage rise in response to engine being increased to about
4,000 rpm.
5. If the voltage is out of specification, proceed the following.
a. Check for the cause of uneven air flow through mass air flow sensor. Refer to following.

Crushed air ducts

Malfunctioning seal of air cleaner element

Uneven dirt of air cleaner element

Improper specification of intake air system parts
b. If NG, repair or replace malfunctioning part and perform step 2 to 4 again.
If OK, go to next step.
6. Turn ignition switch OFF.
7. Disconnect mass air flow sensor harness connector and reconnect it again.
8. Perform step 2 to 4 again.
9. If NG, clean or replace mass air flow sensor.
Without CONSULT-II
1. Reconnect all harness connectors disconnected.
2. Start engine and warm it up to normal operating temperature.
3. Check voltage between ECM terminal 51 (Mass air flow sensor
signal) and ground.
*: Check for linear voltage rise in response to engine being increased to about
4,000 rpm.
4. If the voltage is out of specification, proceed the following.
a. Check for the cause of uneven air flow through mass air flow sensor. Refer to following.

Crushed air ducts

Malfunctioning seal of air cleaner element

Uneven dirt of air cleaner element

Improper specification of intake air system parts
Condition MAS A/F SE-B1 (V)
Ignition switch ON (Engine stopped.) Approx. 0.4
Idle (Engine is warmed-up to normal
operating temperature.)1.0 - 1.3
2,500 rpm (Engine is warmed-up to
normal operating temperature.)1.7 - 2.1
Idle to about 4,000 rpm* 1.0 - 1.3 to Approx. 2.4
PBIB2371E
Condition MAS A/F SE-B1 (V)
Ignition switch ON (Engine stopped.) Approx. 0.4
Idle (Engine is warmed-up to normal
operating temperature.)1.0 - 1.3
2,500 rpm (Engine is warmed-up to
normal operating temperature.)1.7 - 2.1
Idle to about 4,000 rpm* 1.0 - 1.3 to Approx. 2.4
PBIB11 06 E

EC-182Revision: October 2005
DTC P0101 MAF SENSOR
2005 QX56
b. If NG, repair or replace malfunctioning part and perform step 2 to 3 again.
If OK, go to next step.
5. Turn ignition switch OFF.
6. Disconnect mass air flow sensor harness connector and reconnect it again.
7. Perform step 2 and 3 again.
8. If NG, clean or replace mass air flow sensor.
Removal and InstallationUBS00H13
MASS AIR FLOW SENSOR
Refer to EM-14, "AIR CLEANER AND AIR DUCT" .