Infiniti G37 Coupe. Manual — part 731

SERVICE INFORMATION FOR ELECTRICAL INCIDENT

GI-43

< BASIC INSPECTION >

C

D

E

F

G

H

I

J

K

L

M

B

GI

N

O

P

• 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 resistance 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 circuit 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.

SGI853

GI-44

< BASIC INSPECTION >

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 operations 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

SERVICE INFORMATION FOR ELECTRICAL INCIDENT

GI-45

< BASIC INSPECTION >

C

D

E

F

G

H

I

J

K

L

M

B

GI

N

O

P

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 voltage. 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 light 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. Control 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 light 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 voltage

Lower than battery voltage Approx. 8 (Ex-
ample)

Switch OFF

0 V

Approx. 0

2

Body
ground

Lamp

Output

Switch ON

Battery voltage

Approx. 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

0V

Battery 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

GI-46

< BASIC INSPECTION >

CONSULT-III/GST CHECKING SYSTEM

CONSULT-III/GST CHECKING SYSTEM

Description

INFOID:0000000001679207

• When CONSULT-III/GST is connected with a data link connector

(A) equipped on the vehicle side, it will communicate with the con-
trol unit equipped in the vehicle and then enable various kinds of
diagnostic tests.

• Refer to “CONSULT-III Software Operation Manual” for more infor-

mation.

CONSULT-III Function and System Application*1

INFOID:0000000001679208

1

: Instrument driver lower panel

JPAIA0024ZZ

Diagnostic test

mode

Function

ENGINE

TRANSMISS

ION

AIR B

A

G

MET

E

R/M

&

A

BC

M

AUT

O

DRIVE

POS.

ABS (I

nc

lu

di

n

g

VDC)

IPDM E/R

ICC

4W

AS

(FRONT

)

4W

AS(MAIN)/RAS

/HICAS

ADAP

TIVE

LI

GHT

MUL

T

I A

V

PRE CRASH

SEA

T BEL

T

Work support

This mode enables a technician to adjust
some devices faster and more accurately by
following the indications on CONSULT-III.

x

x

-

-

x

-

x

-

x

-

-

x

-

-

Self-diagnostic
results

Self-diagnostic results can be read and
erased quickly.

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Trouble diagnos-
tic record

Current self-diagnostic results and all trouble
diagnostic records previously stored can be
read.

-

-

x

-

-

-

-

-

-

-

-

-

-

-

Data monitor

Input/Output data in the ECU can be read.

x

x

-

x

x

x

x

x

x

x

x

x

x

x

CAN diagnosis

The condition of CAN communication line can
be indicated by a topology.

x

x

x

x

x

x

x

x

x

-

x

x

x

x

CAN diagnosis
support monitor

The condition of CAN communication line can
be read.

x

x

-

x

x

x

x

x

x

x

x

x

x

x

Active test

Diagnostic Test Mode in which CONSULT-III
drives some actuators apart from the ECUs
and also shifts some parameters in a speci-
fied range.

x

-

-

-

x

x

x

x

x

x

x

x

-

-

DTC & SRT con-
firmation

The results of SRT (System Readiness Test)
and the self-diagnosis status/result can be
confirmed.

x

-

-

-

-

-

-

-

-

-

-

-

-

-

DTC work sup-
port

This mode enables a technician to monitor
the status/results of self-diagnosis by the
ECU.

-

x

-

-

-

-

-

-

-

-

-

-

-

-

ECU (ECM/TCM)
part number

ECU (ECM/TCM) part number can be read.

x

x

-

-

x

x

x

x

x

x

x

x

x

x

ECU discriminat-
ed No.

Classification number of a replacement ECU
can be read to prevent an incorrect ECU from
being installed.

-

-

x

-

-

-

-

-

-

-

-

-

-

-