sensor INFINITI QX4 2005 Factory Service Manual

ATC-116
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
SYSTEM DESCRIPTION
The front air control controls compressor operation based on ambient and intake temperature and a signal
from ECM.
Low Temperature Protection Control
The front air control will turn the compressor ON or OFF as determined by a signal detected by the intake sen-
sor and the ambient sensor.
When intake air temperature is higher than the preset value, the compressor turns ON. The compressor turns
OFF when intake air temperature is lower than the preset value. That preset value is dependent on the ambi-
ent temperature, refer to the following table.
DIAGNOSTIC PROCEDURE FOR MAGNET CLUTCH
SYMPTOM: Magnet clutch does not engage when A/C switch is ON.
1. CHECK INTAKE AND AMBIENT SENSOR CIRCUITS
Check intake and ambient sensors. Refer to ATC-55, "
A/C System Self-diagnosis Function" .
OK or NG
OK >> GO TO 2.
NG >>

Malfunctioning intake sensor. Refer to ATC-145, "Intake Sensor Circuit" .

Malfunctioning ambient sensor. Refer to ATC-145, "Intake Sensor Circuit" .
Ambient temperature °C (°F)C om pr e ss o r O N
intake temperature °C (°F)C o m p r e s s o r O F F
intake temperature °C (°F)
0 (32) 2.5 (37) 2.0 (36)
10 (50) 2.5 (37) 2.0 (36)
20 (68) 2.5 (37) 1.5 (35)
30 (86) 2.0 (36) 0.5 (33)
40 (104) 2.0 (36) 0.5 (33)
50 (122) 2.0 (36) 0.5 (33)
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TROUBLE DIAGNOSIS
ATC-119
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8. CHECK REFRIGERANT PRESSURE SENSOR
WITH CONSULT-II
1. Start engine.
2. Check voltage of refrigerant pressure sensor. Refer to ATC-33, "
CONSULT-II Function (HVAC)" .
WITHOUT CONSULT-II
1. Start engine.
2. Check voltage between ECM harness connector F54 terminal
70 (B/W) and ground.
OK or NG
OK >>
WITH CONSULT-II
GO TO 9.

WITHOUT CONSULT-II
GO TO 10.
NG >> Refer to EC-643, "
REFRIGERANT PRESSURE SENSOR" .
9. CHECK BCM INPUT (FAN ON) SIGNAL
Check FAN ON/OFF signal. Refer to ATC-33, "
CONSULT-II Function
(HVAC)" .
OK or NG
OK >> GO TO 12.
NG >> GO TO 10.
10. CHECK CIRCUIT CONTINUITY BETWEEN BCM AND FRONT AIR CONTROL
1. Turn ignition switch OFF.
2. Disconnect BCM connector and front air control connector.
3. Check continuity between BCM harness connector M18 terminal
28 (L/R) and front air control harness connector M49 terminal 10
(L/R).
OK or NG
OK >> GO TO 11.
NG >> Repair harness or connector.
Te r m i n a l s
Condition Voltage (+)
(-)
ECM con-
nectorTe r m i n a l N o .
(Wire color)
F54 70 (B/W) Ground A/C switch: ON Approx. 0.36 - 3.88V
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FRONT BLOWER CONTROL
DIAL ON: FAN ON SIG ON
FRONT BLOWER CONTROL
DIAL OFF: FAN ON SIG OFF
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28 - 10 Continuity should exist.
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ATC-126
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
High-pressure Side is Too Low and Low-pressure Side is Too High
Both High- and Low-pressure Sides are Too Low
Gauge indication Refrigerant cycle Probable cause Corrective action
High-pressure side is too low and
low-pressure side is too high.High- and low-pressure sides
become equal soon after com-
pressor operation stops.Compressor pressure opera-
tion is improper.
↓
Damaged inside compressor
packings.Replace compressor.
No temperature difference
between high- and low-pres-
sure sides.Compressor pressure opera-
tion is improper.
↓
Damaged inside compressor
packings.Replace compressor.
AC356A
Gauge indication Refrigerant cycle Probable cause Corrective action
Both high- and low-pressure sides
are too low.

There is a big temperature
difference between liquid
tank outlet and inlet. Outlet
temperature is extremely
low.

Liquid tank inlet and expan-
sion valve are frosted.Liquid tank inside is slightly
clogged.

Replace liquid tank.

Check lubricant for contami-
nation.

Temperature of expansion
valve inlet is extremely low
as compared with areas
near liquid tank.

Expansion valve inlet may
be frosted.

Temperature difference
occurs somewhere in high-
pressure side.High-pressure pipe located
between liquit tank and expan-
sion valve is clogged.

Check and repair malfunc-
tioning parts.

Check lubricant for contami-
nation.
Expansion valve and liquid
tank are warm or only cool
when touched.Low refrigerant charge.
↓
Leaking fittings or compo-
nents.Check refrigerant system for
leaks. Refer to ATC-189,
"Checking for Refrigerant
Leaks" .
There is a big temperature dif-
ference between expansion
valve inlet and outlet while the
valve itself is frosted.Expansion valve closes a little
compared with the specifica-
tion.
↓
1. Improper expansion valve
adjustment.
2. Malfunctioning expansion
valve.
3. Outlet and inlet may be
clogged.

Remove foreign particles by
using compressed air.

Check lubricant for contami-
nation.
An area of the low-pressure
pipe is colder than areas near
the evaporator outlet.Low-pressure pipe is clogged
or crushed.

Check and repair malfunc-
tioning parts.

Check lubricant for contami-
nation.
Air flow volume is too low. Evaporator is frozen.

Check intake sensor circuit.
Refer to ATC-145, "
Intake
Sensor Circuit" .

Repair evaporator fins.

Replace evaporator.

Refer to AT C - 9 3 , "Front
Blower Motor Circuit" .
AC353A

ATC-128
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
Insufficient HeatingEJS003XX
SYMPTOM: Insufficient heating
INSPECTION FLOW
*1ATC-57, "Operational Check (Front)"
or ATC-60, "
Operational Check
(Rear)"
*2AT C - 7 0 , "Air Mix Door Motor Circuit"*3AT C - 5 5 , "A/C System Self-diagno-
sis Function"
*4ATC-56, "SELF-DIAGNOSIS CODE
CHART"
*5AT C - 9 3 , "Front Blower Motor Circuit"*6EC-195, "DTC P0117, P0118 ECT
SENSOR"
*7EM-12, "Checking Drive Belts"*8ATC-133, "Water Valve Circuit"
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ATC-132
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
Self-diagnosisEJS003XZ
SYMPTOM: Self-diagnosis cannot be performed.
INSPECTION FLOW
*1AT C - 6 1 , "Power Supply and Ground
Circuit for Front Air Control"
*2ATC-137, "Ambient Sensor Circuit"*3ATC-145, "Intake Sensor Circuit"
*4ATC-143, "Optical Sensor Circuit"*5ATC-145, "Intake Sensor Circuit"*6AT C - 7 0 , "Air Mix Door Motor Circuit"
*7AT C - 5 7 , "Operational Check (Front)"*8ATC-38, "SYMPTOM TABLE"
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TROUBLE DIAGNOSIS
ATC-137
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Ambient Sensor CircuitEJS003Y2
COMPONENT DESCRIPTION
Ambient Sensor
The ambient sensor is attached on the radiator core support (left
side). It detects ambient temperature and converts it into a value
which is then input into the front air control.
AMBIENT TEMPERATURE INPUT PROCESS
The front air control includes a processing circuit for the ambient sensor input. However, when the tempera-
ture detected by the ambient sensor increases quickly, the processing circuit retards the front air control func-
tion. It only allows the front air control to recognize an ambient temperature increase of 0.33°C (0.6°F) per 100
seconds.
This prevents constant adjustments due to momentary conditions, such as stopping after high speed driving.
Although the actual ambient temperature has not changed, the temperature detected by the ambient sensor
will increase. This is because the heat from the engine compartment can radiate to the front grille area, loca-
tion of the ambient sensor.
DIAGNOSTIC PROCEDURE FOR AMBIENT SENSOR
SYMPTOM: Ambient sensor circuit is open or shorted. Using the
CONSULT-II, DTC B257B or B257C is displayed. Without a CON-
SULT-II, code 40 or 41 is indicated on front air control as a result of
conducting the front air control self-diagnosis.
1. CHECK VOLTAGE BETWEEN AMBIENT SENSOR AND GROUND
1. Disconnect ambient sensor connector.
2. Turn ignition switch ON.
3. Check voltage between ambient sensor harness connector E1
terminal 1 (P) and ground.
OK or NG
OK >> GO TO 2.
NG >> GO TO 4.
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1 - Ground : Approx. 5V
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ATC-138
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
2. CHECK CIRCUIT CONTINUITY BETWEEN AMBIENT SENSOR AND FRONT AIR CONTROL
1. Turn ignition switch OFF.
2. Disconnect front air control connector.
3. Check continuity between ambient sensor harness connector
E1 terminal 1 (P) and front air control harness connector M49
terminal 17 (P).
OK or NG
OK >> GO TO 3.
NG >> Repair harness or connector.
3. CHECK AMBIENT SENSOR
Refer to ATC-137, "
Ambient Sensor Circuit" .
OK or NG
OK >> 1. Replace front air control. Refer to ATC-147, "FRONT AIR CONTROL"
2. Go to self-diagnosis AT C - 5 5 , "A/C System Self-diagnosis Function" and perform self-diagno-
sis.
NG >> 1. Replace ambient sensor.
2. Go to self-diagnosis AT C - 5 5 , "
A/C System Self-diagnosis Function" and perform self-diagno-
sis.
4. CHECK CIRCUIT CONTINUITY BETWEEN AMBIENT SENSOR AND FRONT AIR CONTROL
1. Turn ignition switch OFF.
2. Disconnect front air control connector.
3. Check continuity between ambient sensor harness connector
E1 terminal 2 (V/R) and front air control harness connector M49
terminal 21 (V/R).
4. Check continuity between ambient sensor harness connector
E1 terminal 2 (V/R) and ground.
OK or NG
OK >> 1. Replace front air control. Refer to ATC-147, "FRONT AIR CONTROL"
2. Go to self-diagnosis AT C - 5 5 , "A/C System Self-diagnosis Function" and perform self-diagno-
sis.
NG >> Repair harness or connector.1 - 17 : Continuity should exist.
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2 - 21 : Continuity should exist.
2 - Ground : Continuity should not exist.
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TROUBLE DIAGNOSIS
ATC-139
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Revision: October 20052005 QX56
COMPONENT INSPECTION
Ambient Sensor
After disconnecting ambient sensor connector E1, measure resis-
tance between terminals 1 and 2 at sensor component side, using
the table below.
If NG, replace ambient sensor.
Temperature °C (°F) Resistance kΩ
−15 (5) 12.73
−10 (14) 9.92
−5 (23) 7.80
0 (32) 6.19
5 (41) 4.95
10 (50) 3.99
15 (59) 3.24
20 (68) 2.65
25 (77) 2.19
30 (86) 1.81
35 (95) 1.51
40 (104) 1.27
45 (113) 1.07
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ATC-140
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
In-vehicle Sensor CircuitEJS003Y3
COMPONENT DESCRIPTION
In-vehicle Sensor
The in-vehicle sensor is located on instrument lower driver panel. It
converts variations in temperature of passenger compartment air
(drawn in through the integrated fan) into a resistance value. It is
then input into the front air control.
WJIA0822E
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TROUBLE DIAGNOSIS
ATC-141
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Revision: October 20052005 QX56
DIAGNOSTIC PROCEDURE FOR IN-VEHICLE SENSOR
SYMPTOM: in-vehicle sensor circuit is open or shorted. Using the
CONSULT-II, DTC B2578 or B2579 is displayed. Without a CON-
SULT-II, code 30 or 31 is indicated on front air control as a result of
conducting the front air control self-diagnosis.
1. CHECK IN-VEHICLE SENSOR CIRCUIT
Are diagnostic codes 30, 31 or DTC B2578, B2579 present?
YES or NO
YES >> GO TO 6.
NO >> GO TO 2.
2. CHECK VOLTAGE BETWEEN IN-VEHICLE SENSOR AND GROUND
1. Disconnect in-vehicle sensor connector.
2. Turn ignition switch ON.
3. Check voltage between in-vehicle sensor harness connector
M32 terminal 4 (LG/R) and ground.
OK or NG
OK >> GO TO 3.
NG >> GO TO 5.
3. CHECK CIRCUIT CONTINUITY BETWEEN IN-VEHICLE SENSOR AND FRONT AIR CONTROL
1. Turn ignition switch OFF.
2. Disconnect front air control connector M49.
3. Check continuity between in-vehicle sensor harness connector
M32 terminal 1 (V/R) and front air control harness connector
M49 terminal 21 (V/R).
OK or NG
OK >> GO TO 4.
NG >> Repair harness or connector.
4. CHECK IN-VEHICLE SENSOR
Refer to ATC-145, "
Intake Sensor Circuit" .
OK or NG
OK >> 1. Replace front air control. Refer to ATC-147, "FRONT AIR CONTROL" .
2. Go to AT C - 5 5 , "
A/C System Self-diagnosis Function" and perform self-diagnosis.
NG >> 1. Replace in-vehicle sensor. Refer to ATC-149, "
IN-VEHICLE SENSOR" .
2. Go to AT C - 5 5 , "
A/C System Self-diagnosis Function" and perform self-diagnosis.
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4 - Ground : Approx. 5V.
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1 - 21 : Continuity should exist.
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