2004 INFINITI QX56 engine

EC-544Revision: August 2007
DTC P1574 ASCD VEHICLE SPEED SENSOR
2004 QX56
DTC P1574 ASCD VEHICLE SPEED SENSORPFP:31036
Component DescriptionUBS00HBM
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-647, "
AUTOMATIC SPEED CONTROL DEVICE (ASCD)" for ASCD functions.
On Board Diagnosis LogicUBS00HBN
This self-diagnosis has the one trip detection logic.
The MIL will not light up for this diagnosis.
NOTE:

If DTC P1574 is displayed with DTC U1000, U1001, first perform the trouble diagnosis for DTC
U1000, U1001. Refer to EC-135, "
DTC U1000, U1001 CAN COMMUNICATION LINE" .

If DTC P1574 is displayed with DTC P0500, first perform the trouble diagnosis for DTC P0500.
Refer to EC-340, "
DTC P0500 VSS".

If DTC P1574 is displayed with DTC P0605, first perform the trouble diagnosis for DTC P0605.
Refer to EC-351, "
DTC P0605 ECM".
DTC Confirmation ProcedureUBS00HBO
CAUTION:
Always drive vehicle at a safe speed.
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:
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.
WITH CONSULT-II
1. Start engine (VDC switch OFF).
2. Select “DATA MONITOR” mode with CONSULT-II.
3. Drive the vehicle at more than 40 km/h (25 MPH).
4. If DTC is detected, go to EC-545, "
Diagnostic Procedure" .
WITH GST
Follow the procedure “WITH CONSULT-II” above.
DTC No.Trouble Diagnosis
NameDTC Detecting Condition Possible Cause
P1574
1574ASCD vehicle speed
sensorECM 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
SEF 0 58 Y

EC-546Revision: August 2007
DTC P1706 PNP SWITCH
2004 QX56
DTC P1706 PNP SWITCHPFP:32006
Component DescriptionUBS00HBQ
When the gear position is P or N, park/neutral position (PNP) switch is ON.
TCM detects the position because the continuity of the line (the ON signal) exists.
Then the TCM sends the PNP switch signal to the ECM via combination meter.
CONSULT-II Reference Value in Data Monitor ModeUBS00HBR
Specification data are reference values.
On Board Diagnosis LogicUBS00HBS
DTC Confirmation ProcedureUBS00HBT
CAUTION:
Always drive vehicle at a safe speed.
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.
WITH CONSULT-II
1. Turn ignition switch ON.
2. Select “P/N POSI SW” in “DATA MONITOR” mode with CON-
SULT-II. Then check the “P/N POSI SW” signal under the follow-
ing conditions.
If NG, go to EC-549, "
Diagnostic Procedure" .
If OK, go to following step.
3. Select “DATA MONITOR” mode with CONSULT-II.
4. Start engine and warm it up to normal operating temperature.
5. Maintain the following conditions for at least 60 consecutive sec-
onds.
6. If 1st trip DTC is detected, go to EC-549, "
Diagnostic Procedure"
.
MONITOR ITEM CONDITION SPECIFICATION
P/N POSI SW

Ignition switch: ONShift lever: P or N ON
Shift lever: Except above OFF
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1706
1706Park/neutral position
switchThe signal of the park/neutral position (PNP)
switch is not changed in the process of engine
starting and driving.

Harness or connectors
[The park/neutral position (PNP) switch
circuit is open or shorted.]

Park/neutral position (PNP) switch

Combination meter

TCM
Position (Selector lever) Known-good signal
N or P position ON
Except the above position OFF
ENG SPEED More than 1,000 rpm
COOLAN TEMP/S More than 70°C (158°F)
B/FUEL SCHDL More than 2.0 msec
VHCL SPEED SE More than 64 km/h (40 MPH)
Selector lever Suitable position
SEF 2 12 Y
SEF 2 13 Y

DTC P1805 BRAKE SWITCH
EC-551
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Revision: August 20072004 QX56
DTC P1805 BRAKE SWITCHPFP:25320
DescriptionUBS00HBX
Brake switch signal is applied to the ECM through the stop lamp switch when the brake pedal is depressed.
This signal is used mainly to decrease the engine speed when the vehicle is driving.
CONSULT-II Reference Value in Data Monitor ModeUBS00HBY
Specification data are reference values.
On Board Diagnosis LogicUBS00HBZ
The MIL will not light up for this diagnosis.
FAIL-SAFE MODE
When the malfunction is detected, the ECM enters fail-safe mode.
DTC Confirmation ProcedureUBS00HC0
WITH CONSULT-II
1. Turn ignition switch ON.
2. Fully depress the brake pedal for at least 5 seconds.
3. Erase the DTC with CONSULT-II.
4. Select “DATA MONITOR” mode with CONSULT-II.
5. If 1st trip DTC is detected, go to EC-553, "
Diagnostic Procedure"
.
WITH GST
Follow the procedure “WITH CONSULT-II” above.
MONITOR ITEM CONDITION SPECIFICATION
BRAKE SW

Ignition switch: ONBrake pedal: Fully released OFF
Brake pedal: Slightly depressed ON
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P1805
1805Brake switchA brake switch signal is not sent to ECM for an
extremely long time while the vehicle is driving.

Harness or connectors
(Stop lamp switch circuit is open or
shorted.)

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
SEF 0 58 Y

EC-556Revision: August 2007
DTC P2122, P2123 APP SENSOR
2004 QX56
DTC P2122, P2123 APP SENSORPFP:18002
Component DescriptionUBS00HC4
The accelerator pedal position sensor is installed on the upper end
of the accelerator pedal assembly. The sensor detects the accelera-
tor position and sends a signal to the ECM.
Accelerator pedal position sensor has two sensors. These sensors
are a kind of potentiometers which transform the accelerator pedal
position into output voltage, and emit the voltage signal to the ECM.
In addition, these sensors detect the opening and closing speed of
the accelerator pedal and feed the voltage signals to the ECM. The
ECM judges the current opening angle of the accelerator pedal from
these signals and controls the throttle control motor based on these
signals.
Idle position of the accelerator pedal is determined by the ECM
receiving the signal from the accelerator pedal position sensor. The ECM uses this signal for the engine oper-
ation such as fuel cut.
CONSULT-II Reference Value in Data Monitor ModeUBS00HC5
Specification data are reference values.
*: Accelerator pedal position sensor 2 signal is converted by ECM internally. Thus, it differ from ECM terminal voltage.
On Board Diagnosis LogicUBS00HC6
These self-diagnoses have the one trip detection logic.
NOTE:
If DTC P2122 or P2123 is displayed with DTC P1229, first perform the trouble diagnosis for DTC P1229.
Refer to EC-424, "
DTC P1229 SENSOR POWER SUPPLY" .
FAIL -S AFE M OD E
When the malfunction is detected, ECM enters fail-safe mode and the MIL lights up.
PBIB1741E
MONITOR ITEM CONDITION SPECIFICATION
ACCEL SEN1

Ignition switch: ON
(Engine stopped)Accelerator pedal: Fully released 0.5 - 1.0V
Accelerator pedal: Fully depressed 4.2 - 4.8V
ACCEL SEN2*

Ignition switch: ON
(Engine stopped)Accelerator pedal: Fully released 0.5 - 1.0V
Accelerator pedal: Fully depressed 4.2 - 4.8V
CLSD THL POS

Ignition switch: ON
(Engine stopped)Accelerator pedal: Fully released ON
Accelerator pedal: Slightly depressed OFF
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P2122
2122Accelerator pedal position
sensor 1 circuit low inputAn excessively low voltage from the APP sen-
sor 1 is sent to ECM.

Harness or connectors
(The APP sensor 1 circuit is open or
shorted.)

Accelerator pedal position sensor
(Accelerator pedal position sensor 1) P2123
2123Accelerator pedal position
sensor 1 circuit high inputAn excessively high voltage from the APP sen-
sor 1 is sent to ECM.
Engine operating condition in fail-safe mode
The ECM controls the electric throttle control actuator in regulating the throttle opening in order for the idle position to be within +10
degrees.
The ECM regulates the opening speed of the throttle valve to be slower than the normal condition.
So, the acceleration will be poor.

DTC P2122, P2123 APP SENSOR
EC-557
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Revision: August 20072004 QX56
DTC Confirmation ProcedureUBS00HC7
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 more than 8V at idle.
WITH CONSULT-II
1. Turn ignition switch ON.
2. Select “DATA MONITOR” mode with CONSULT-II.
3. Start engine and let it idle for 1 second.
4. If DTC is detected, go to EC-559, "
Diagnostic Procedure" .
WITH GST
Follow the procedure “WITH CONSULT-II” above.
SEF 0 58 Y

DTC P2122, P2123 APP SENSOR
EC-559
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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 ProcedureUBS00HC9
1. CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten three ground screws on the body.
Refer to EC-133, "
Ground Inspection" .
OK or NG
OK >> GO TO 2.
NG >> Repair or replace ground connections.
TER-
MINAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
82 B/RSensor ground
(APP sensor 1)[Engine is running]

Warm-up condition

Idle speedApproximately 0V
83 G/WSensor ground
(APP sensor 2)[Engine is running]

Warm-up condition

Idle speedApproximately 0V
90 LSensor power supply
(APP sensor 1)[Ignition switch: ON]Approximately 5V
91 W/RSensor power supply
(APP sensor 2)[Ignition switch: ON]Approximately 5V
98 G/RAccelerator pedal position
sensor 2[Ignition switch: ON]

Engine stopped

Accelerator pedal: Fully released0.25 - 0.50V
[Ignition switch: ON]

Engine stopped

Accelerator pedal: Fully depressed2.0 - 2.5V
106 BR/WAccelerator pedal position
sensor 1[Ignition switch: ON]

Engine stopped

Accelerator pedal: Fully released0.5 - 1.0V
[Ignition switch: ON]

Engine stopped

Accelerator pedal: Fully depressed4.2 - 4.8V
BBIA0354E

EC-562Revision: August 2007
DTC P2127, P2128 APP SENSOR
2004 QX56
DTC P2127, P2128 APP SENSORPFP:18002
Component DescriptionUBS00HCC
The accelerator pedal position sensor is installed on the upper end
of the accelerator pedal assembly. The sensor detects the accelera-
tor position and sends a signal to the ECM.
Accelerator pedal position sensor has two sensors. These sensors
are a kind of potentiometers which transform the accelerator pedal
position into output voltage, and emit the voltage signal to the ECM.
In addition, these sensors detect the opening and closing speed of
the accelerator pedal and feed the voltage signals to the ECM. The
ECM judges the current opening angle of the accelerator pedal from
these signals and controls the throttle control motor based on these
signals.
Idle position of the accelerator pedal is determined by the ECM
receiving the signal from the accelerator pedal position sensor. The ECM uses this signal for the engine oper-
ation such as fuel cut.
CONSULT-II Reference Value in Data Monitor ModeUBS00HCD
Specification data are reference values.
*: Accelerator pedal position sensor 2 signal is converted by ECM internally. Thus, it differ from ECM terminal voltage.
On Board Diagnosis LogicUBS00HCE
These self-diagnoses have the one trip detection logic.
FAIL -S AFE M OD E
When the malfunction is detected, ECM enters fail-safe mode and the MIL lights up.
PBIB1741E
MONITOR ITEM CONDITION SPECIFICATION
ACCEL SEN1

Ignition switch: ON
(Engine stopped)Accelerator pedal: Fully released 0.5 - 1.0V
Accelerator pedal: Fully depressed 4.2 - 4.8V
ACCEL SEN2*

Ignition switch: ON
(Engine stopped)Accelerator pedal: Fully released 0.5 - 1.0V
Accelerator pedal: Fully depressed 4.2 - 4.8V
CLSD THL POS

Ignition switch: ON
(Engine stopped)Accelerator pedal: Fully released ON
Accelerator pedal: Slightly depressed OFF
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P2127
2127Accelerator pedal position
sensor 2 circuit low inputAn excessively low voltage from the APP
sensor 2 is sent to ECM.

Harness or connectors
(APP sensor 2 circuit is open or shorted.)
(TP sensor circuit is shorted.)

Accelerator pedal position sensor
(Accelerator pedal position sensor 2)

Electric throttle control actuator
(TP sensor) P2128
2128Accelerator pedal position
sensor 2 circuit high inputAn excessively high voltage from the APP
sensor 2 is sent to ECM.
Engine operating condition in fail-safe mode
The ECM controls the electric throttle control actuator in regulating the throttle opening in order for the idle position to be within +10
degrees.
The ECM regulates the opening speed of the throttle valve to be slower than the normal condition.
So, the acceleration will be poor.

DTC P2127, P2128 APP SENSOR
EC-563
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Revision: August 20072004 QX56
DTC Confirmation ProcedureUBS00HCF
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 more than 8V at idle.
WITH CONSULT-II
1. Turn ignition switch ON.
2. Select “DATA MONITOR” mode with CONSULT-II.
3. Start engine and let it idle for 1 second.
4. If DTC is detected, go to EC-565, "
Diagnostic Procedure" .
WITH GST
Follow the procedure “WITH CONSULT-II” above.
SEF 0 58 Y