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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ATC-117
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2. PERFORM AUTO ACTIVE TEST
Refer to PG-22, "
Auto Active Test" .
Does magnet clutch operate?
YES or NO
YES >>
WITH CONSULT-II
GO TO 5.

WITHOUT CONSULT-II
GO TO 6.
NO >> Check 10A fuse (No. 42, located in IPDM E/R), and GO TO 3.
3. CHECK CIRCUIT CONTINUITY BETWEEN IPDM E/R AND COMPRESSOR
1. Turn ignition switch OFF.
2. Disconnect IPDM E/R connector and compressor (magnet
clutch) connector.
3. Check continuity between IPDM E/R harness connector E119
terminal 11 (Y/B) and compressor harness connector F3 termi-
nal 1 (Y/B).
OK or NG
OK >> GO TO 4.
NG >> Repair harness or connector.
4. CHECK MAGNET CLUTCH CIRCUIT
Check for operation sound when applying battery voltage direct cur-
rent to terminal.
OK or NG
OK >> Replace IPDM E/R. Refer to PG-28, "Removal and
Installation of IPDM E/R" .
NG >> Replace magnet clutch. Refer to ATC-180, "
Removal
and Installation for Compressor Clutch" .
5. CHECK BCM INPUT (COMPRESSOR ON) SIGNAL
Check compressor ON/OFF signal. Refer to ATC-33, "
CONSULT-II
Function (HVAC)" .
OK or NG
OK >> GO TO 8.
NG >> GO TO 6.
11 – 1 : Continuity should exist.
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A/C SW ON : COMP ON SIG ON
A/C SW OFF : COMP ON SIG OFF
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ATC-118
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
6. 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
27 (W/R) and front air control harness connector M49 terminal
12 (W/R).
OK or NG
OK >> GO TO 7.
NG >> Repair harness or connector.
7. CHECK VOLTAGE FOR FRONT AIR CONTROL (COMPRESSOR ON SIGNAL)
1. Reconnect BCM connector and front air control connector.
2. Turn ignition switch ON.
3. Check voltage between front air control harness connector M49
terminal 12 (W/R) and ground.
OK or NG
OK >> GO TO 8.
NG-1 >> If the voltage is approx. 5V when A/C switch is ON, replace front air control. Refer to ATC-147,
"FRONT AIR CONTROL" .
NG-2 >> If the voltage is approx. 0V when A/C switch is OFF, replace BCM. Refer to BCS-20, "
Removal
and Installation of BCM" . 27 - 12 Continuity should exist.
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Terminals
Condition Voltage (+)
(-) Front air
control con-
nectorTe r m i n a l N o .
(Wire color)
M49 12 (W/R) GroundA/C switch: ON Approx. 0V
A/C switch: OFF Approx. 5V
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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-120
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
11 . CHECK VOLTAGE FOR FRONT AIR CONTROL (FAN ON SIGNAL)
1. Reconnect BCM connector and front air control connector.
2. Turn ignition switch ON.
3. Check voltage between front air control harness connector M49
terminal 10 (L/R) and ground.
OK or NG
OK >> GO TO 12.
NG-1 >> If the voltage is approx. 5V when blower motor is ON, replace front air control. Refer to ATC-147,
"FRONT AIR CONTROL" .
NG-2 >> If the voltage is approx. 0V when blower motor is OFF, replace BCM. Refer to BCS-20, "
Removal
and Installation of BCM" .
12. CHECK CAN COMMUNICATION
Check CAN communication. Refer to LAN-5, "
CAN COMMUNICATION" .

BCM – ECM

ECM – IPDM E/R

ECM – Front air control
OK or NG
OK >> Inspection End.
NG >> Repair or replace malfunctioning part(s).
Terminals
Condition Voltage (+)
(-)
Front air con-
trol connectorTe r m i n a l N o .
(Wire color)
M49 10 (L/R) GroundA/C switch: ON
Blower motor
operatesApprox. 0V
A/C switch: OFF Approx. 5V
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ATC-121
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Insufficient CoolingEJS003XW
SYMPTOM: Insufficient cooling
INSPECTION FLOW
*1AT C - 5 7 , "Operational Check
(Front)"
*2AT C - 5 5 , "A/C System Self-diagno-
sis Function"
*3ATC-56, "SELF-DIAGNOSIS CODE
CHART"
*4EC-440, "SYSTEM DESCRIPTION"*5AT C - 5 , "Contaminated Refrigerant"*6ATC-122, "PERFORMANCE TEST
DIAGNOSES"
*7ATC-124, "Test Reading"*8EM-12, "Checking Drive Belts"*9ATC-133, "Water Valve Circuit"
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ATC-122
TROUBLE DIAGNOSIS
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PERFORMANCE TEST DIAGNOSES
*1ATC-124, "PERFORMANCE
CHART"
*2ATC-124, "PERFORMANCE
CHART"
*3ATC-125, "Trouble Diagnoses for
Unusual Pressure"
*4AT C - 7 0 , "Air Mix Door Motor Circuit"
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ATC-123
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*1ATC-180, "Removal and Installation
for Compressor Clutch"
*2AT C - 9 3 , "Front Blower Motor Circuit"*3EM-12, "Checking Drive Belts"
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ATC-124
TROUBLE DIAGNOSIS
Revision: October 20052005 QX56
PERFORMANCE CHART
Test Condition
Testing must be performed as follows:
Test Reading
Recirculating-to-discharge Air Temperature Table
Ambient Air Temperature-to-operating Pressure Table
Vehicle location Indoors or in the shade (in a well-ventilated place)
Doors Closed
Door window Open
Hood Open
TEMP. Max. COLD
Mode switch
(Ventilation) set
Recirculation (REC) switch
(Recirculation) set
Blower speedMax. speed set
Engine speed Idle speed
Operate the air conditioning system for 10 minutes before taking measurements.
Inside air (Recirculating air) at blower assembly inlet
Discharge air temperature at center ventilator
°C (°F) Relative humidity
%Air temperature
°C (°F)
50 - 6020 (68) 5.3 - 6.5 (42 - 44)
25 (77) 9.7 - 11.5 (49 - 53)
30 (86) 13.8 - 16.3 (57 - 61)
35 (95) 18.0 - 21.2 (64 - 70)
40 (104) 22.2 - 25.7 (72 - 78)
60 - 7020 (68) 6.5 - 7.7 (44 - 46)
25 (77) 11.5 - 13.3 (53 - 56)
30 (86) 16.3 - 18.8 (61 - 66)
35 (95) 21.2 - 24.0 (70 - 75)
40 (104) 25.7 - 29.2 (78 - 85)
Ambient air
High-pressure (Discharge side)
kPa (kg/cm
2 , psi)Low-pressure (Suction side)
kPa (kg/cm2 , psi) Relative humidity
%Air temperature
°C (°F)
50 - 7020 (68)680 - 840
(6.94 - 8.57, 98.6 - 121.8)160 - 198
(1.63 - 2.02, 23.2 - 28.7)
25 (77)800 - 985
(8.16 - 10.05, 116.0 - 142.8)198 - 245
(2.02 - 2.50, 28.7 - 35.5)
30 (86)940 - 1,150
(9.59 - 11.73, 136.3 - 166.8)225 - 278
(2.30 - 2.84, 32.6 - 40.3)
35 (95)1,160 - 1,410
(11.83 - 14.38, 168.2 - 204.5)273 - 335
(2.78 - 3.42, 39.6 - 48.6)
40 (104)1,325 - 1,620
(13.52 - 16.52, 192.1 - 234.9)325 - 398
(3.32 - 4.06, 47.1 - 57.7)

TROUBLE DIAGNOSIS
ATC-125
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TROUBLE DIAGNOSES FOR UNUSUAL PRESSURE
Whenever system′s high and/or low side pressure is unusual, diagnose using a manifold gauge. The marker
above the gauge scale in the following tables indicates the standard (usual) pressure range. Since the stan-
dard (usual) pressure, however, differs from vehicle to vehicle, refer to above table (Ambient air temperature-
to-operating pressure table).
Both High- and Low-pressure Sides are Too High
High-pressure Side is Too High and Low-pressure Side is Too Low
Gauge indication Refrigerant cycle Probable cause Corrective action
Both high- and low-pressure sides
are too high.Pressure is reduced soon
after water is splashed on
condenser.Excessive refrigerant charge
in refrigeration cycleReduce refrigerant until speci-
fied pressure is obtained.
Air suction by cooling fan is
insufficient.Insufficient condenser cooling
performance
↓
1. Condenser fins are clogged.
2. Improper fan rotation of
cooling fan

Clean condenser.

Check and repair cooling fan
if necessary.

Low-pressure pipe is not
cold.

When compressor is
stopped high-pressure
value quickly drops by
approximately 196 kPa (2
kg/cm
2 , 28 psi). It then
decreases gradually there-
after.Poor heat exchange in con-
denser
(After compressor operation
stops, high-pressure
decreases too slowly.)
↓
Air in refrigeration cycleEvacuate and recharge sys-
tem.
Engine tends to overheat.Engine cooling systems mal-
function.Check and repair engine cool-
ing system.

An area of the low-pres-
sure pipe is colder than
areas near the evaporator
outlet.

Plates are sometimes cov-
ered with frost.

Excessive liquid refrigerant
on low-pressure side

Excessive refrigerant dis-
charge flow

Expansion valve is open a
little compared with the
specification.
↓
Improper expansion valve
adjustmentReplace expansion valve.
AC359A
Gauge indication Refrigerant cycle Probable cause Corrective action
High-pressure side is too high and
low-pressure side is too low.
Upper side of condenser and
high-pressure side are hot,
however, liquid tank is not so
hot.High-pressure tube or parts
located between compressor
and condenser are clogged or
crushed.

Check and repair or replace
malfunctioning parts.

Check lubricant for contami-
nation.
AC360A