2009 INFINITI QX56 check engine light

EC-308
< COMPONENT DIAGNOSIS >[VK56DE]
P1550 BATTERY CURRENT SENSOR
P1550 BATTERY CURRENT SENSOR
Component DescriptionINFOID:0000000003771605
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
CHG-7, "System
Description".
: Vehicle front
CAUTION:
Do not connect the electrical compon ent or the ground wire directly to the battery terminal. The con-
nection causes the malfunction of th e power generation voltage variable control, and then the battery
discharge may occur.
On Board Diagn osis LogicINFOID:0000000003771606
The MIL will not light up for this self-diagnosis.
NOTE:
If DTC P1550 is displayed with DTC P0643, first pe rform the trouble diagnosis for DTC P0643. Refer to
EC-285
.
DTC Confirmation ProcedureINFOID:0000000003771607
If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-
ing the next step.
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.
TESTING CONDITION:
Before performing the following procedure, confirm that battery voltage is more than 8V at idle.
1. Start engine and wait at least 10 seconds.
2. Check 1st trip DTC.
3. If 1st trip DTC is detected, go to EC-308, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771608
1.CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten ground screws on the body.
BBIA0744E
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1550
1550 Battery current sensor circuit
range/performance The 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
Revision: December 20092009 QX56

EC-312
< COMPONENT DIAGNOSIS >[VK56DE]
P1551, P1552 BATTERY CURRENT SENSOR
P1551, P1552 BATTERY CURRENT SENSOR
Component DescriptionINFOID:0000000003771610
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
CHG-7, "System
Description".
: Vehicle front
CAUTION:
Do not connect the electrical compon ent or the ground wire directly to the battery terminal. The con-
nection causes the malfunction of th e power generation voltage variable control, and then the battery
discharge may occur.
On Board Diagn osis LogicINFOID:0000000003771611
The MIL will not light up for these self-diagnoses.
NOTE:
If DTC P1551 or P1552 is displayed with DTC P0643, first perform the trouble diagnosis for DTC P0643.
Refer to EC-285, "On Board Diagnosis Logic"
.
DTC Confirmation ProcedureINFOID:0000000003771612
If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-
ing the next step.
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.
TESTING CONDITION:
Before performing the following procedure, confirm th at battery voltage is more than 8V with ignition
switch ON
1. Turn ignition switch ON.
2. Wait at least 10 seconds.
3. Check 1st trip DTC.
4. If 1st trip DTC is detected, go to EC-312, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771613
1.CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten ground screws on the body.
BBIA0744E
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1551
1551 Battery current sensor circuit
low input An excessively low voltage from the sensor
is sent to ECM.
 Harness or connectors
(The sensor circuit is open or shorted.)
 Battery current sensor
P1552
1552 Battery current sensor circuit
high input An excessively high voltage from the sensor
is sent to ECM.
Revision: December 20092009 QX56

EC-316
< COMPONENT DIAGNOSIS >[VK56DE]
P1553 BATTERY CURRENT SENSOR
P1553 BATTERY CURRENT SENSOR
Component DescriptionINFOID:0000000003771615
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
CHG-7, "System
Description".
: Vehicle front
CAUTION:
Do not connect the electrical compon ent or the ground wire directly to the battery terminal. The con-
nection causes the malfunction of th e power generation voltage variable control, and then the battery
discharge may occur.
On Board Diagn osis LogicINFOID:0000000003771616
The MIL will not light up for this self-diagnosis.
NOTE:
If DTC P1553 is displayed with DTC P0643, first pe rform the trouble diagnosis for DTC P0643. Refer to
EC-285
.
DTC Confirmation ProcedureINFOID:0000000003771617
If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-
ing the next step.
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.
TESTING CONDITION:
Before performing the following procedure, confirm that battery voltage is more than 8V at idle.
1. Start engine and wait at least 10 seconds.
2. Check 1st trip DTC.
3. If 1st trip DTC is detected, go to EC-316, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771618
1.CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten ground screws on the body.
BBIA0744E
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1553
1553 Battery current sensor performance The signal voltage transmitted from the
sensor to ECM is higher than the amount
of the maximum power generation.  Harness or connectors
(The sensor circuit is open or shorted.)
 Battery current sensor
Revision: December 20092009 QX56

EC-320
< COMPONENT DIAGNOSIS >[VK56DE]
P1554 BATTERY CURRENT SENSOR
P1554 BATTERY CURRENT SENSOR
Component DescriptionINFOID:0000000003771620
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
CHG-7, "System
Description".
: Vehicle front
CAUTION:
Do not connect the electrical compon ent or the ground wire directly to the battery terminal. The con-
nection causes the malfunction of th e power generation voltage variable control, and then the battery
discharge may occur.
On Board Diagn osis LogicINFOID:0000000003771621
The MIL will not light up for this self-diagnosis.
NOTE:
If DTC P1554 is displayed with DTC P0643, first pe rform the trouble diagnosis for DTC P0643. Refer to
EC-285, "On Board Diagnosis Logic"
.
Overall Function CheckINFOID:0000000003771622
Use this procedure to check the overall function of the bat tery current sensor circuit. During this check, a 1st
trip DTC might not be confirmed.
TESTING CONDITION:
 Before performing the following procedure, confirm th at battery voltage is more than 12.8V at idle.
 Before performing the following procedure, confi rm that all load switches and A/C switch are turned
OFF.
WITH CONSULT-III
1. Start engine and let it idle.
2. Select “BAT CUR SEN” in “DATA MONITOR” mode with CONSULT-III.
3. Check “BAT CUR SEN” indication for 10 seconds.
“BAT CUR SEN” should be above 2,300mV at least once.
4. If NG, go to EC-321, "Diagnosis Procedure"
.
WITH GST
1. Start engine and let it idle.
BBIA0744E
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1554
1554 Battery current sensor performance The output voltage of the battery current
sensor is lower than the specified value
while the battery voltage is high enough.  Harness or connectors
(The sensor circuit is open or shorted.)
 Battery current sensor
Revision: December 20092009 QX56

EC-344
< COMPONENT DIAGNOSIS >[VK56DE]
P1574 ICC VEHICLE SPEED SENSOR
P1574 ICC VEHICLE SPEED SENSOR
Component DescriptionINFOID:0000000003771648
The ECM receives two vehicle speed signals via CAN communication line. One is sent from “unified meter and
A/C amp.”, and the other is from TCM (Transmission
control module). The ECM uses these signals for ICC
control. Refer to CCS-13
for ICC functions.
On Board Diagnosis LogicINFOID:0000000003771649
This self-diagnosis has the one trip detection logic.
 The MIL will not light up for this self-diagnosis.
NOTE:
 If DTC P1574 is displayed with DTC U1000, U1001, first perform the trouble diagnosis for DTC U1000,
U1001. Refer to EC-86, "On Board Diagnosis Logic"
.
 If DTC P1574 is displayed with DTC P0607, first pe rform the trouble diagnosis for DTC P0607. Refer
to EC-284, "On Board Diagnosis Logic"
.
 If DTC P1574 is displayed with DTC P0500, first pe rform the trouble diagnosis for DTC P0500. Refer
to EC-271, "On Board Diagnosis Logic"
.
 If DTC P1574 is displayed with DTC P0605, first pe rform the trouble diagnosis for DTC P0605. Refer
to EC-282, "On Board Diagnosis Logic"
.
DTC Confirmation ProcedureINFOID:0000000003771650
CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-
ing the next step.
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.
TESTING CONDITION:
Step 3 may be conducted with the drive wheels lifted in the shop or by driving the vehicle. If a road test
is expected to be easier, it is unnecessary to lift the vehicle.
1. Start engine.
2. Drive the vehicle at more than 40 km/h (25MPH).
3. Check 1st trip DTC.
4. If DTC is detected, go to EC-344, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771651
1.CHECK DTC WITH TCM
Check DTC with TCM. Refer to TM-30, "OBD-II Diagnostic Trouble Code (DTC)"
.
OK or NG
OK >> GO TO 2.
NG >> Perform trouble shooting relevant to DTC indicated.
2.CHECK DTC WITH “ABS ACTUATOR A ND ELECTRIC UNIT (CONTROL UNIT)”
Refer to BRC-24, "CONSULT-III Function (ABS)"
.
DTC No. Trouble Diagnosis Name DTC Detecting Condition Possible Cause
P1574
1574 ICC vehicle speed sensor ECM detects a difference between two vehicle
speed signals is out of the specified range.  Harness or connectors
(The CAN communication line is open or
shorted.)
 Combination meter
 ABS actuator and electric unit (control unit)
 Wheel sensor
TCM
ECM
Revision: December 20092009 QX56

EC-346
< COMPONENT DIAGNOSIS >[VK56DE]
P1574 ASCD VEHICL
E SPEED SENSOR
P1574 ASCD VEHICLE SPEED SENSOR
Component DescriptionINFOID:0000000003771652
The ECM receives two vehicle speed sensor signals via CAN communication line. One is sent from combina-
tion meter and the other is from TCM (Transmission control module). The ECM uses these signals for ASCD
control. Refer to EC-33, "System Description"
for ASCD functions.
On Board Diagnosis LogicINFOID:0000000003771653
This self-diagnosis has the one trip detection logic.
 The MIL will not light up for this self-diagnosis.
NOTE:
 If DTC P1574 is displayed with DTC U1000, U1001, first perform the trouble diagnosis for DTC U1000,
U1001. Refer to EC-86, "DTC Confirmation Procedure"
.
 If DTC P1574 is displayed with DTC P0607, first pe rform the trouble diagnosis for DTC P0607. Refer
to EC-284, "On Board Diagnosis Logic"
.
 If DTC P1574 is displayed with DTC P0500, first pe rform the trouble diagnosis for DTC P0500. Refer
to EC-271, "On Board Diagnosis Logic"
.
 If DTC P1574 is displayed with DTC P0605, first pe rform the trouble diagnosis for DTC P0605. Refer
to EC-282, "On Board Diagnosis Logic"
.
DTC Confirmation ProcedureINFOID:0000000003771654
CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-
ing the next step.
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.
TESTING CONDITION:
Step 3 may be conducted with the drive wheels lifted in the shop or by driving the vehicle. If a road test
is expected to be easier, it is unnecessary to lift the vehicle.
1. Start engine (VDC switch OFF).
2. Drive the vehicle at more than 40 km/h (25 MPH).
3. Check DTC.
4. If DTC is detected, go to EC-346, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771655
1.CHECK DTC WITH TCM
Check DTC with TCM. Refer to TM-30, "OBD-II Diagnostic Trouble Code (DTC)"
.
OK or NG
OK >> GO TO 2.
NG >> Perform trouble shooting relevant to DTC indicated.
2.CHECK DTC WITH ABS ACTUATOR AN D ELECTRIC UNIT (CONTROL UNIT)
DTC No.Trouble Diagnosis
Name DTC Detecting Condit
ion Possible Cause
P1574
1574 ASCD vehicle speed
sensor ECM detects a difference between two vehicle
speed signals is out of the specified range.  Harness or connectors
(The CAN communication line is open or
shorted.)
 Combination meter
 ABS actuator and electric unit (control unit)
 Wheel sensor
TCM
ECM
Revision: December 20092009 QX56

EC-348
< COMPONENT DIAGNOSIS >[VK56DE]
P1805 BRAKE SWITCH
P1805 BRAKE SWITCH
DescriptionINFOID:0000000003771656
Brake switch signal is applied to the ECM through t
he stop lamp switch when the brake pedal is depressed.
This signal is used mainly to decrease the engine speed when the vehicle is driving.
On Board Diagn osis LogicINFOID:0000000003771657
The MIL will not light up for this self-diagnosis.
FAIL-SAFE MODE
When the malfunction is detected, the ECM enters fail-safe mode.
DTC Confirmation ProcedureINFOID:0000000003771658
1. Turn ignition switch ON.
2. Fully depress the brake pedal for at least 5 seconds.
3. Erase the DTC with CONSULT-III.
4. Check 1st trip DTC.
5. If 1st trip DTC is detected, go to EC-348, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771659
1.CHECK STOP LAMP SWITCH CIRCUIT
1. Turn ignition switch OFF.
2. Check the stop lamp when depressing and releasing the brake pedal.
OK or NG
OK >> GO TO 4.
NG >> GO TO 2.
2.CHECK STOP LAMP SWIT CH POWER SUPPLY CIRCUIT
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1805
1805 Brake switch A brake switch signal is not sent to ECM for ex-
tremely long time while the vehicle is driving.  Harness or connectors
(Stop lamp switch circuit is open or short-
ed.)
 Stop lamp switch
Engine operating condition in fail-safe mode
ECM controls the electric throttle control actuator by regulating the throttle opening to a small range.
Therefore, acceleration will be poor. Vehicle condition Driving condition
When engine is idling Normal When accelerating Poor acceleration
Brake pedal Stop lamp
Fully released Not illuminated
Slightly depressed Illuminated
Revision: December 20092009 QX56

P2100, P2103 THROTTLE CONTROL MOTOR RELAY
EC-351
< COMPONENT DIAGNOSIS > [VK56DE]
C
D
E
F
G H
I
J
K L
M A
EC
NP
O
P2100, P2103 THROTTLE CONTROL MOTOR RELAY
Component DescriptionINFOID:0000000003771661
Power supply for the throttle control motor is provided to
the ECM via throttle control motor relay. The throttle
control motor relay is ON/OFF controlled by the ECM. When the ignition switch is turned ON, the ECM sends
an ON signal to throttle control motor relay and batte ry voltage is provided to the ECM. When the ignition
switch is turned OFF, the ECM sends an OFF signal to throttle control motor relay and battery voltage is not
provided to the ECM.
On Board Diagnosis LogicINFOID:0000000003771662
These self-diagnoses have the on e trip detection logic.
FAIL-SAFE MODE
When the malfunction is detected, ECM ent ers fail-safe mode and the MlL lights up.
DTC Confirmation ProcedureINFOID:0000000003771663
NOTE:
If DTC Confirmation Procedure has been previously conduc ted, always perform the following before conduct-
ing the next step.
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.
PROCEDURE FOR DTC P2100
1. Turn ignition switch ON and wait at least 2 seconds.
2. Start engine and let it idle for 5 seconds.
3. Check DTC.
4. If DTC is detected, go to EC-351, "Diagnosis Procedure"
.
PROCEDURE FOR DTC P2103
TESTING CONDITION:
Before performing the following procedure, c onfirm that battery voltage is more than 8V.
1. Turn ignition switch ON and wait at least 1 second.
2. Check DTC.
3. If DTC is detected, go to EC-351, "Diagnosis Procedure"
.
Diagnosis ProcedureINFOID:0000000003771664
1.CHECK THROTTLE CONTROL MOTOR RELAY POWER SUPPLY CIRCUIT-I
1. Turn ignition switch OFF.
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P2100
2100 Throttle control motor
relay circuit open ECM detects a voltage of power source for
throttle control motor is excessively low.  Harness or connectors
(Throttle control motor relay circuit is
open)
 Throttle control motor relay
P2103
2103 Throttle control motor
relay circuit short ECM detect the throttle control motor relay is
stuck ON.  Harness or connectors
(Throttle control motor relay circuit is
shorted)
 Throttle control motor relay
Engine operating condition in fail-safe mode
ECM stops the electric throttle control actuator control, throttle valve is maintained at a fixed opening (approx. 5 degrees) b y the return
spring.
Revision: December 20092009 QX56