2007 INFINITI QX56 service

DTC P1421 COLD START CONTROL
EC-481
< SERVICE INFORMATION >
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DTC P1421 COLD START CONTROL
DescriptionINFOID:0000000003532007
ECM controls ignition timing and engine idle speed when engine is started with prewarming up condition.
This control promotes the activation of three way catalyst by heating the catalyst and reduces emissions.
On Board Diagnosis LogicINFOID:0000000003532008
DTC Confirmation ProcedureINFOID:0000000003532009
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.
•If DTC P1421 is displayed with other DTC, first perform the trouble diagnosis for other DTC.
TESTING CONDITION:
Before performing the following procedure, confirm that battery voltage is more than 11V at idle.
WITH CONSULT-II
1. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON.
3. Select “DATA MONITOR” mode with CONSULT-II.
4. Check that the “COOLAN TEMP/S” indication is between 4°C
(39°F) and 36°C (97°F).
If “COOLAN TEMP/S” indication is within the specified value, go
to the following step.
If “COOLANT TEMP/S” indication is out of the specified value,
cool engine down or warm engine up and go to step 1.
5. Start engine and let it idle for 5 minutes.
6. If 1st trip DTC is detected, go to EC-481, "
Diagnosis Procedure".
WITH GST
Follow the procedure “WITH CONSULT-II” above.
Diagnosis ProcedureINFOID:0000000003532010
1.PERFORM IDLE AIR VOLUME LEARNING
Perform EC-78, "
Idle Air Volume Learning".
Is Idle Air Volume Learning carried out successfully?
Ye s o r N o
Yes >> GO TO 2.
No >> Follow the instruction of Idle Air Volume Learning.
2.CHECK INTAKE SYSTEM
Check for the cause of intake air volume lacking. Refer to the following.
• Crushed intake air passage
• Intake air passage clogging
OK or NG
OK >> GO TO 3.
NG >> Repair or replace malfunctioning part
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1421
1421Cold start emission reduction
strategy monitoringECM does not control ignition timing and engine
idle speed properly when engine is started with
prewarming up condition.• Lack of intake air volume
• Fuel injection system
•ECM
SEF174Y

EC-482
< SERVICE INFORMATION >
DTC P1421 COLD START CONTROL
3.CHECK FUEL INJECTION SYSTEM FUNCTION
Perform EC-292, "
DTC Confirmation Procedure" in DTC P0171, P0174 FUEL INJECTION SYSTEM FUNC-
TION.
OK or NG
OK >> GO TO 4.
NG >> Go to EC-297, "
Diagnosis Procedure".
4.PERFORM DTC CONFIRMATION PROCEDURE
With CONSULT-II
1. Turn ignition switch ON.
2. Select “SELF DIAG RESULTS” mode with CONSULT-II.
3. Touch “ERASE”.
4.Perform DTC Confirmation Procedure.
See EC-481, "
DTC Confirmation Procedure".
5. Is the 1st trip DTC P1421 displayed again?
With GST
1. Turn ignition switch ON.
2. Select Service $04 with GST.
3.Perform DTC Confirmation Procedure.
See EC-481, "
DTC Confirmation Procedure".
4. Is the 1st trip DTC P1421 displayed again?
Ye s o r N o
Ye s > > G O T O 5 .
No >>INSPECTION END
5.REPLACE ECM
1. Replace ECM.
2. Perform initialization of IVIS (NATS) system and registration of all IVIS (NATS) ignition key IDs.
Refer to BL-117, "
ECM Re-communicating Function".
3. Perform EC-77, "
VIN Registration".
4. Perform EC-77, "
Accelerator Pedal Released Position Learning".
5. Perform EC-77, "
Throttle Valve Closed Position Learning".
6. Perform EC-78, "
Idle Air Volume Learning".
>>INSPECTION END

DTC P1550 BATTERY CURRENT SENSOR
EC-483
< SERVICE INFORMATION >
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DTC P1550 BATTERY CURRENT SENSOR
Component DescriptionINFOID:0000000003532011
The power generation voltage variable control enables fuel con-
sumption to be decreased by reducing the engine load which is
caused by the power generation of the generator. The battery cur-
rent sensor (1) is installed to the battery cable at the negative termi-
nal. The sensor measures the charging/discharging current of the
battery. Based on the sensor signal, ECM judges whether or not the
power generation voltage variable control is performed. When per-
forming the power generation voltage variable control, ECM calcu-
lates the target power generation voltage based on the sensor
signal. And ECM sends the calculated value as the power genera-
tion command value to IPDM E/R. For the details of the power gen-
eration voltage variable control, refer to SC section.
CAUTION:
Do not connect the electrical component or the ground wire directly to the battery terminal. The con-
nection causes the malfunction of the power generation voltage variable control, and then the battery
discharge may occur.
CONSULT-II Reference Value in Data Monitor ModeINFOID:0000000003532012
Specification data are reference values.
*: Before measuring the terminal voltage, confirm that the battery is fully charged. Refer to SC-4, "How to Handle Battery".
On Board Diagnosis LogicINFOID:0000000003532013
The MIL will not light up for this self-diagnosis.
NOTE:
If DTC P1550 is displayed with DTC P0643, first perform the trouble diagnosis for DTC P0643. Refer to
EC-447
.
DTC Confirmation ProcedureINFOID:0000000003532014
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 8V at idle.
WITH CONSULT-II
1. Turn ignition switch ON.
BBIA0744E
MONITOR ITEM CONDITION SPECIFICATION
BAT CUR SEN• Engine speed: Idle
• Battery: Fully charged*
• Selector lever: P or N
• Air conditioner switch: OFF
•No loadApprox. 2,600 - 3,500mV
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1550
1550Battery current sensor circuit
range/performanceThe output voltage of the battery current
sensor remains within the specified
range while engine is running.• Harness or connectors
(The sensor circuit is open or shorted.)
• Battery current sensor

EC-484
< SERVICE INFORMATION >
DTC P1550 BATTERY CURRENT SENSOR
2. Select “DATA MONITOR” mode with CONSULT-II.
3. Start engine and wait at least 10 seconds.
4. If 1st trip DTC is detected, go to EC-486, "
Diagnosis Procedure".
WITH GST
Follow the procedure “WITH CONSULT-II” above.
SEF058Y

DTC P1550 BATTERY CURRENT SENSOR
EC-485
< SERVICE INFORMATION >
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Wiring DiagramINFOID:0000000003532015
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.
BBWA2767E

EC-486
< SERVICE INFORMATION >
DTC P1550 BATTERY CURRENT SENSOR
*: Before measuring the terminal voltage, confirm that the battery is fully charged. Refer to SC-4, "How to Handle Battery".
Diagnosis ProcedureINFOID:0000000003532016
1.CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten ground screws on the body.
Refer to EC-143, "
Ground Inspection".
OK or NG
OK >> GO TO 2.
NG >> Repair or replace ground connections.
2.CHECK BATTERY CURRENT SENSOR POWER SUPPLY CIRCUIT
1. Disconnect battery current sensor (1) harness connector.
2. Turn ignition switch ON.
TER-
MI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
49 R/YSensor power supply
(Battery current sensor)[Ignition switch: ON]Approximately 5V
67 BSensor ground
(Battery current sensor)[Engine is running]
•Warm-up condition
• Idle speedApproximately 0V
71 R Battery current sensor[Engine is running]
• Battery: Fully charged*
• Idle speedApproximately 2.6 - 3.5V
BBIA0354E
BBIA0744E

DTC P1550 BATTERY CURRENT SENSOR
EC-487
< SERVICE INFORMATION >
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3. Check voltage between battery current sensor terminal 1 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
• Harness for open or short between battery current sensor and ECM
>> Repair open circuit or short to ground or short to power in harness or connectors.
4.CHECK BATTERY CURRENT SENSOR GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Check harness continuity between battery current sensor terminal 2 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 6.
NG >> GO TO 5.
5.DETECT MALFUNCTIONING PART
Check the following.
• Harness connectors E5, F14
• Harness for open or short between battery current sensor and ECM
>> Repair open circuit or short to ground or short to power in harness or connectors.
6.CHECK BATTERY CURRENT SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between battery current sensor terminal 3 and ECM terminal 71.
Refer to Wiring Diagram.
2. Also check harness for short to ground and short to power.
OK or NG
OK >> GO TO 8.
NG >> GO TO 7.
7.DETECT MALFUNCTIONING PART
Check the following.
• Harness connectors E2, F32
• Harness for open or short between battery current sensor and ECM
>> Repair open circuit or short to ground or short to power in harness or connectors.
8.CHECK BATTERY CURRENT SENSOR
Refer to EC-488, "
Component Inspection". Voltage: Approximately 5V
PBIA9891J
Continuity should exist.
Continuity should exist.

EC-488
< SERVICE INFORMATION >
DTC P1550 BATTERY CURRENT SENSOR
OK or NG
OK >> GO TO 9.
NG >> Replace battery negative cable assembly.
9.CHECK INTERMITTENT INCIDENT
Refer to EC-138
.
>>INSPECTION END
Component InspectionINFOID:0000000003532017
BATTERY CURRENT SENSOR
1. Reconnect harness connectors disconnected.
2. Disconnect battery negative cable (1).
• : To body ground
3. Install jumper cable (A) between battery negative terminal and
body ground.
4. Turn ignition switch ON.
5. Check voltage between ECM terminal 71 (battery current sensor
signal) and ground.
6. If NG, replace battery negative cable assembly.
BBIA0745E
Voltage: Approximately 2.5V
PBIB2617E