INFINITI QX56 2008 Factory Service Manual

SERVICE INFORMATION FOR ELECTRICAL INCIDENTGI-39
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lowing section illustrates ways to simulate the c onditions/environment under which the owner experiences an
electrical incident.
The section is broken into the six following topics:• Vehicle vibration
• Heat sensitive
• Freezing
• Water intrusion
• Electrical load
• Cold or hot start up
Get a thorough description of the incident from the customer . It is important for simulating the conditions of the
problem.
VEHICLE VIBRATION
The problem may occur or become worse while driving on a rough road or when engine is vibrating (idle with
A/C on). In such a case, you will want to check for a vibration related condition. Refer to the following illustra-
tion.
Connector & Harness
Determine which connectors and wiring harness would affect the electrical system you are inspecting. Gently
shake each connector and harness while monitoring the syst em for the incident you are trying to duplicate.
This test may indicate a loose or poor electrical connection.
Hint
Connectors can be exposed to moisture. It is possible to get a thin film of corrosion on the connector termi-
nals. A visual inspection may not reveal this without disconnecting the connector. If the problem occurs inter-
mittently, perhaps the problem is caused by corrosi on. It is a good idea to disconnect, inspect and clean the
terminals on related connectors in the system.
Sensor & Relay
Gently apply a slight vibration to sensors and relays in the system you are inspecting.
This test may indicate a loose or poorly mounted sensor or relay.
Engine Compartment
There are several reasons a vehicle or engine vibration could cause an electrical complaint. Some of the
things to check for are:
• Connectors not fully seated.
• Wiring harness not long enough and is being stressed due to engine vibrations or rocking.
• Wires laying across brackets or moving components.
• Loose, dirty or corroded ground wires.
• Wires routed too close to hot components.
To inspect components under the hood, start by verifyi ng the integrity of ground connections. (Refer to Ground
Inspection described later.) First check that the system is properly grounded. Then check for loose connection
by gently shaking the wiring or components as previous ly explained. Using the wiring diagrams inspect the
wiring for continuity.
Behind the Instrument Panel
An improperly routed or improperly clamped harness can become pinched during accessory installation. Vehi-
cle vibration can aggravate a harness which is routed along a bracket or near a screw.
Under Seating Areas
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SERVICE INFORMATION FOR ELECTRICAL INCIDENT
An unclamped or loose harness can cause wiring to be pinched by seat components (such as slide guides)
during vehicle vibration. If the wiring runs under s eating areas, inspect wire routing for possible damage or
pinching.
HEAT SENSITIVE
• The customer's concern may occur during hot weather or after car has sat for a short time. In such cases you will want to check for a
heat sensitive condition.
• To determine if an electrical component is heat sensitive, heat the component with a heat gun or equivalent.
CAUTION:
Do not heat components above 60 °C (140° ).
• If incident occurs while heating the unit, either replace or properly insulate the component.
FREEZING
• The customer may indicate the incident goes away after the carwarms up (winter time). The cause could be related to water freez-
ing somewhere in the wiring/electrical system.
• There are two methods to check for this. The first is to arrange for the owner to leave his car overnight. Make sure it will get cold
enough to demonstrate his complaint. Leave the car parked out-
side overnight. In the morning, do a quick and thorough diagnosis
of those electrical components which could be affected.
• The second method is to put the suspect component into a freezer long enough for any water to freeze. Reinstall the part into the car
and check for the reoccurrence of the incident. If it occurs, repair or
replace the component.
WATER INTRUSION
The incident may occur only during high humidity or in rainy/snowy
weather. In such cases the incident could be caused by water intru-
sion on an electrical part. This can be simulated by soaking the car
or running it through a car wash.
CAUTION:
Do not spray water directly on any electrical components.
ELECTRICAL LOAD
The incident may be electrical load sensitive. Perform diagnosis with
all accessories (including A/C, rear window defogger, radio, fog
lamps) turned on.
COLD OR HOT START UP
On some occasions an electrical incident may occur only when the car is started cold, or it may occur when
the car is restarted hot shortly after being turned off. In these cases you may have to keep the car overnight to
make a proper diagnosis.
SGI842
SGI843
SGI844
SGI845
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Circuit InspectionINFOID:0000000001539227
DESCRIPTION
• In general, testing electrical circuits is an easy task if it is approached in a logical and organized method. Before beginning it is important to have all available information on the system to be tested. Also, get a thor-
ough understanding of system operation. Then you will be able to use the appropriate equipment and follow
the correct test procedure.
• You may have to simulate vehicle vibrations while te sting electrical components. Gently shake the wiring
harness or electrical component to do this.
NOTE:
Refer to GI-35, "
How to Check Terminal" to probe or check terminal.
TESTING FOR “OPENS” IN THE CIRCUIT
Before you begin to diagnose and test the system, you should rough sketch a schematic of the system. This
will help you to logically walk through the diagnosis process. Drawing the sketch will also reinforce your work-
ing knowledge of the system.
Continuity Check Method
The continuity check is used to find an open in the circui t. The digital multimeter (DMM) set on the resistance
function will indicate an open circuit as over limit (no beep tone or no ohms symbol). Make sure to always start
with the DMM at the highest resistance level.
To help in understanding the diagnosis of open circui ts, please refer to the previous schematic.
• Disconnect the battery negative cable.
• Start at one end of the circuit and work your way to the other end. (At the fuse block in this example)
• Connect one probe of the DMM to the fuse block terminal on the load side.
• Connect the other probe to the fuse block (power) side of SW1. Little or no resistance will indicate that por-
tion of the circuit has good continuity. If there were an open in the circuit, the DMM would indicate an over
limit or infinite resistance condition. (point A)
• Connect the probes between SW1 and the relay. Little or no resistance will indicate that portion of the circuit
has good continuity. If there were an open in the circuit, t he DMM would indicate an over limit or infinite resis-
tance condition. (point B)
• Connect the probes between the relay and the solenoid. Little or no resistance will indicate that portion of the
circuit has good continuity. If there were an open in the ci rcuit, the DMM would indicate an over limit or infi-
nite resistance condition. (point C)
Any circuit can be diagnosed using the approach in the previous example.
Voltage Check Method
To help in understanding the diagnosis of open circuits please refer to the previous schematic.
In any powered circuit, an open can be found by methodica lly checking the system for the presence of voltage.
This is done by switching the DMM to the voltage function.
• Connect one probe of the DMM to a known good ground.
• Begin probing at one end of the circuit and work your way to the other end.
• With SW1 open, probe at SW1 to check for voltage. voltage; open is further down the circuit than SW1.
OPEN A circuit is open when there is no continuity through a section of the circuit.
SHORT There are two types of shorts.
• SHORT CIRCUIT
When a circuit contacts another circuit and causes the normal resistance to
change.
• SHORT TO GROUND When a circuit contacts a ground source and grounds the circuit.
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SERVICE INFORMATION FOR ELECTRICAL INCIDENT
no voltage; open is between fuse block and SW1 (point A).
• Close SW1 and probe at relay. voltage; open is further down the circuit than the relay.
no voltage; open is between SW1 and relay (point B).
• Close the relay and probe at the solenoid. voltage; open is further down the circuit than the solenoid.
no voltage; open is between relay and solenoid (point C).
Any powered circuit can be diagnosed using the approach in the previous example.
TESTING FOR “SHORTS” IN THE CIRCUIT
To simplify the discussion of shorts in the system, please refer to the following schematic.
Resistance Check Method
• Disconnect the battery negative cable and remove the blown fuse.
• Disconnect all loads (SW1 open, relay disconnected and solenoid disconnected) powered through the fuse.
• Connect one probe of the DMM to the load side of the fuse terminal. Connect the other probe to a known good ground.
• With SW1 open, check for continuity. continuity; short is between fuse terminal and SW1 (point A).
no continuity; short is further down the circuit than SW1.
• Close SW1 and disconnect the relay. Put probes at the load side of fuse terminal and a known good ground. Then, check for continuity.
continuity; short is between SW1 and the relay (point B).
no continuity; short is further down the circuit than the relay.
• Close SW1 and jump the relay contacts with jumper wire. Put probes at the load side of fuse terminal and a known good ground. Then, check for continuity.
continuity; short is between relay and solenoid (point C).
no continuity; check solenoid, retrace steps.
Voltage Check Method
• Remove the blown fuse and disconnect all loads (i.e. SW1 open, relay disconnected and solenoid discon-
nected) powered through the fuse.
• Turn the ignition key to the ON or START position. Verify battery voltage at the battery + side of the fuse ter- minal (one lead on the battery + terminal side of the fuse block and one lead on a known good ground).
• With SW1 open and the DMM leads across both fuse terminals, check for voltage. voltage; short is between fuse block and SW1 (point A).
no voltage; short is further down the circuit than SW1.
• With SW1 closed, relay and solenoid disconnected and the DMM leads across both fuse terminals, check for voltage.
voltage; short is between SW1 and the relay (point B).
no voltage; short is further down the circuit than the relay.
• With SW1 closed, relay contacts jumped with fused jumper wire check for voltage. voltage; short is down the circuit of the relay or between the relay and the disconnected solenoid (point C).
no voltage; retrace steps and check power to fuse block.
GROUND INSPECTION
• Ground connections are very important to the proper operation of electrical and electronic circuits. Ground
connections are often exposed to moisture, dirt and other corrosive elements. The corrosion (rust) can
become an unwanted resistance. This unwanted resistance can change the way a circuit works.
• Electronically controlled circuits are very sens itive to proper grounding. A loose or corroded ground can
drastically affect an electronically controlled circuit. A poor or corroded ground can easily affect the circuit.
Even when the ground connection looks clean, there c an be a thin film of rust on the surface.
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• When inspecting a ground connection follow these rules:
- Remove the ground bolt or screw.
- Inspect all mating surfaces for tarnish, dirt, rust, etc.
- Clean as required to assure good contact.
- Reinstall bolt or screw securely.
- Inspect for “add-on” accessories which may be interfering with the ground circuit.
- If several wires are crimped into one ground eyelet terminal, check for proper crimps. Make sure all of the wires are clean, securely fastened and providing a good ground path. If multiple wires are cased in one eye-
let make sure no ground wires have excess wire insulation.
• For detailed ground distribution information, refer to “Ground Distribution” in PG section.
VOLTAGE DROP TESTS
• Voltage drop tests are often used to find components or circuits which have excessive resistance. A voltage drop in a circuit is caused by a resistance when the circuit is in operation.
• Check the wire in the illustration. When measuring re sistance with DMM, contact by a single strand of wire
will give reading of 0 ohms. This would indicate a good circuit. When the circuit operates, this single strand
of wire is not able to carry the current. The single strand will have a high resistance to the current. This will
be picked up as a slight voltage drop.
• Unwanted resistance can be caused by many situations as follows:
- Undersized wiring (single strand example)
- Corrosion on switch contacts
- Loose wire connections or splices.
• If repairs are needed always use wire that is of the same or larger gauge.
Measuring Voltage Drop — Accumulated Method
• Connect the DMM across the connector or part of the ci rcuit you want to check. The positive lead of the
DMM should be closer to power and the negative lead closer to ground.
• Operate the circuit.
• The DMM will indicate how many volts are being used to “push” current through that part of the circuit.
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SERVICE INFORMATION FOR ELECTRICAL INCIDENT
Note in the illustration that there is an excessive 4.1 volt drop between the battery and the bulb.
Measuring Voltage Drop — Steb-by-Step
• The step-by-step method is most useful for isolating excessive drops in low voltage systems (such as those
in “Computer Controlled Systems”).
• Circuits in the “Computer Controlled System” operate on very low amperage.
• The (Computer Controlled) system oper ations can be adversely affected by any variation in resistance in the
system. Such resistance variation may be caused by poor connection, improper installation, improper wire
gauge or corrosion.
• The step by step voltage drop test can identify a component or wire with too much resistance.
CONTROL UNIT CIRCUIT TEST
System Description
• When the switch is ON, the control unit lights up the lamp.
CASE 1
SGI974
SAIA0258E
MGI034A
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INPUT-OUTPUT VOLTAGE CHART
• The voltage value is based on the body ground.
• *: If high resistance exists in the switch side circuit (caused by a single strand), terminal 1 does not detect battery voltag e. Control unit
does not detect the switch is ON even if the switch does not turn ON. Therefore, the control unit does not supply power to ligh t up the
lamp.
CASE 2
INPUT-OUTPUT VOLTAGE CHART
• The voltage value is based on the body ground.
• *: If high resistance exists in the switch side circuit (caused by a single strand), terminal 2 does not detect approx. 0V. Co ntrol unit
does not detect the switch is ON even if the switch does not turn ON. Therefore, the control unit does not control ground to li ght up the
lamp. Terminal No. Description
Condition Value (Approx.)In case of high resistance such as single
strand (V) *
+ −Signal name Input/
Output
1 Body
ground Switch Input Switch ON
Battery voltageLower than battery voltage Approx. 8 (Ex-
ample)
Switch OFF 0 V Approx. 0
2 Body
ground Lamp Output Switch ON
Battery voltage App rox. 0 (Inoperative lamp)
Switch OFF 0 V Approx. 0
Terminal No. Description
Condition Value (Approx.)In case of high resistance such as single
strand (V) *
+ −Signal name Input/
Output
1 Body
ground Lamp Output Switch ON
0VBattery voltage (Inoperative lamp)
Switch OFF Battery voltage Battery voltage
2 Body
ground Switch Input Switch ON
0 V Higher than 0 Approx. 4 (Example)
Switch OFF 5 V Approx. 5
MGI035A
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CONSULT-III CHECKING SYSTEM
CONSULT-III CHECKING SYSTEM
DescriptionINFOID:0000000001539228
• When CONSULT-III is connected with a data link connectorequipped on the vehicle side, it will communicate with the control
unit equipped in the vehicle and then enable various kinds of diag-
nostic tests.
• Refer to “CONSULT-III Operation Manual” for more information.
Function and System ApplicationINFOID:0000000001555032
1 : Hood release handle
2 : Data link connector
ALBIA0047ZZ
Diagnostic test mode Function
ENGINE
TRANSMISSION
ICC
*1
ABS
AIR BAG
IPDM E/R
BCM
METER/M&A
INTELLIGENT KEY
AUTO DRIVE POS.
REARVIEW CAMERA
AIR LEVELIZER MULTI AV
ALL MODE AWD/4WD
*2
HVAC
SONAR
Work support This mode enables a technician to adjust some devic-
es faster and more accurately by following the indica-
tions on CONSULT-III. x - xx - - x - xxxx - - - -
Self-diagnostic Self-diagnostic can be performed quickly. ----x-----------
Self-diagnostic re-
sults Self-diagnostic results can be read and erased quick-
ly.
xxxx - xxxxx - xxxxx
Trouble diagnostic
record Current self-diagnostic results and all trouble diag-
nostic records previously stored can be read.
--- - x--- - -------
Data monitor Input/Output data in the ECM can be read. xxxx - xxxxxxxxxxx
Data monitor (spec)Data monitor specification can be read. x---------------
CAN diagnosis The condition of CAN communication can be indicat-
ed by a topology.
xxxxxxxxxx - - xxx -
CAN diagnosis sup-
port monitor The communication condition of CAN communication
line can be read.
xxxx - xxxxx - - xxx -
Active test Diagnostic Test Mode in which CONSULT-III drives
some actuators apart from the ECMs and also shifts
some parameters in a specified range. x-xx-xx-xx-x- - - -
Function test This mode can show results of self-diagnosis of ECU
with either “OK” or “NG”. For engines, more practical
tests regarding sensors/switches and/or actuators
are available. xxxxx - - - x
-------
DTC & SRT confir-
mation The results of SRT (System Readiness Test) and the
self-diagnosis status/result can be confirmed.
x-x-----x-------
DTC work support The operating condition to confirm Diagnosis Trouble
Codes can be selected. xxx-----x-------
ECM/ECU part num-
ber ECM/ECU part number can be read.
xxxx - - x - xxxxx - xx
ECU discriminated
No. Classification number of a replacement ECU can be
read to prevent an incorrect ECU from being in-
stalled.
----x-----------
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x : Applicable
*1: With intelligent cruise control
*2: With 4-wheel drive
*3: With security card installed
CONSULT-III Data Link Connector (DLC) CircuitINFOID:0000000001555031
INSPECTION PROCEDURE
If the CONSULT-III cannot diagnose the sys tem properly, check the following items.
NOTE:
The CAN and DDL2 circuits from DLC pins 6, 7 and 14 may be connected to more than one system. A short in
any circuit connected to a control unit in one system may affect CONSULT-III access to other systems.
Passenger AirbagDisplays the STATUS (readiness) of the front passen-
ger air bag. ----x-----------
AV COMM monitor The condition of AV communication can be indicated.------------x---
Configuration Sets control module parame
ters to match vehicle op-
tions. ------x---------
PIN read
*3This mode shows the BCM-specific 5-digit code. ------x---------
Control unit initial-
ization
*3All registered ignition key IDs in NATS components
can be initialized and new IDs can be registered. ------x---------
Diagnostic test
mode Function
ENGINE
TRANSMISSION
ICC
*1
ABS
AIR BAG
IPDM E/R BCM
METER/M&A
INTELLIGENT KEY
AUTO DRIVE POS.
REARVIEW CAMERA AIR LEVELIZER MULTI AV
ALL MODE AWD/4WD
*2
HVAC
SONAR
Symptom Check item
CONSULT-III cannot access
any system. • CONSULT-III DLC power supply circuit (Terminal 8) and ground circuit (Terminal 4)
CONSULT-III cannot access in-
dividual system. (Other sys-
tems can be accessed.) • Power supply and ground circuit for the control unit of the system (For detailed circuit, refer to wiring
diagram for each system.)
• Open or short circuit between the system and CONSULT-III DLC (For detailed circuit, refer to wiring diagram for each system.)
• Open or short circuit CAN communication line. Refer to LAN-14, "
Trouble Diagnosis Flow Chart".
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GI-48
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CONSULT-III CHECKING SYSTEM
Wiring Diagram
INFOID:0000000001539231
AAAWA0005GB
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