Isuzu N-Series. Manual

6E-12 EMISSION AND ELECTRICAL DIAGNOSIS

Parts for Electrical Circuit

Wiring

Wire Color
All wires have color-coded insulation.
Wires belonging to a system’s main harness will have a
single color. Wires belonging to a system’s sub circuits
will have a colored stripe. Striped wires use the following
code to show wire size and colors.

Abbreviations are used to indicate wire color within a cir-
cuit diagram.
Refer to the following table.

Legend

1. Colored stripe
2. Single color

Example: 0.5 G R

Red (Stripe color)

Green (Base color)

Wire size (0.5 mm)

N6A1416E

N6A1125E

Legend

1. Stripe color
2. Outside diameter
3. Base color
4. Cross sectional area

N6A1126E

EMISSION AND ELECTRICAL DIAGNOSIS 6E-13

Wire Color Coding

Stripe Color Coding

Wire Size
The size of wire, used in a circuit is determined by the
amount of current (amperage), the length of the circuit,
and the voltage drop allowed. The following wire size
and load capacity, shown below, are specified by JIS
(Japanese Industrial Standard) (Nominal size means
approximate cross sectional area)

Color-coding

Meaning

Color-coding

Meaning

Black

Brown

White

Light green

Red

Gray

Green

Pink

Yellow

Sky blue

Blue

Violet

Orange

Color-code

Base Color

Stripe Color

Blue

Black

Orange

Black

Pink

Black

Pink

Green

Pink

Blue

Red

Yellow

Violet

Red

Violet

White

Yellow

Black

Yellow

Green

Yellow

Violet

N6A1127E

Legend

1. Outside diameter
2. Cross sectional area

6E-14 EMISSION AND ELECTRICAL DIAGNOSIS

Nominal size

(mm)

Cross sectional area

(mm

)

Outside diameter

(mm)

Allowable current (A)

0.3

0.372

1.8

0.5

0.563

0.85

0.885

2.2

1.25

1.287

2.5

2.091

2.9

3.296

3.6

37.5

5.227

4.4

7.952

5.5

13.36

20.61

8.2

EMISSION AND ELECTRICAL DIAGNOSIS 6E-15

DIAGNOSIS (4HE1-TC Only)

Strategy-based Diagnostics

Strategy-Based Diagnostics
The strategy-based diagnostic is a uniform approach to
repair all Electrical/Electronic (E/E) systems. The diag-
nostic flow can always be used to resolve an E/E system
problem and is a starting point when repairs are neces-
sary. The following steps will instruct the technician how
to proceed with a diagnosis:

1. Verify the customer complaint.

• To verify the customer complaint, the techni-

cian should know the normal operation of the
system.

2. Perform preliminary checks.

• Conduct a thorough visual inspection.
• Review the service history.
• Detect unusual sounds or odors.
• Gather diagnostic trouble code information to

achieve an effective repair.

3. Check bulletins and other service information.

• This includes videos, newsletters, etc.

4. Refer to service information (manual) system

check (s).

• “System checks” contain information on a sys-

tem that may not be supported by one or more
DTCs.
System checks verify proper operation of the
system. This will lead the technician in an orga-
nized approach to diagnostics.

5. Refer to service diagnostics.

Diagnostic Trouble Code (DTC) Stored
Follow the designated DTC chart exactly to make an ef-
fective repair.
No DTC
Select the symptom from the symptom tables.
Follow the diagnostic paths or suggestions to complete
the repair. You may refer to the applicable component/
system check in the system checks.
No Matchig Symptom

1. Analyze the complaint.
2. Develop a plan for diagnostics.
3. Utilize the wiring diagrams and the theory of oper-

ation.

Call technical assistance for similar cases where repair
history may be available. Combine technician knowl-
edge with efficient use of the available service informa-
tion.
Intermittents
Conditions that are not always present are called inter-
mittents. To resolve intermittents, perform the following
steps:

1. Observe history DTCs, DTC modes.
2. Evaluate the symptoms and the conditions de-

scribed by the customer.

3. Use a check sheet or other method to identify the

circuit or electrical system component.

4. Follow the suggestions for intermittent diagnosis

found in the service documentation.

Most scan tool, such as the Tech II have data-capturing
capabilities that can assist in detecting intermittents.
No Trouble Found
This condition exists when the vehicle is found to oper-
ate normally. The condition described by the customer
may be normal. Verify the customer complaint against
another vehicle that is operating normally. The condition
may be intermittent. Verify the complaint under the con-
ditions described by the customer before releasing the
vehicle.

1. Re-examine the complaint

When the Complaint cannot be successfully found
or isolated, a re-evaluation is necessary.
The complaint should be re-verified and could be
intermittent as defined in Intermittents, or could be
normal.

2. Repair and verify.

After isolating the cause, the repairs should be
made.
Validate for proper operation and verify that the
symptom has been corrected. This may involve
road testing or other methods to verify that the
complaint has been resolved under the following
conditions:

• Conditions noted by the customer.
• If a DTC was diagnosed, verify a repair by du-

plicating conditions present according to cus-
tomer complaint.

Verifying Vehicle Repair
Verification of the vehicle repair will be more compre-
hensive for vehicles with OBD system diagnostics. Fol-
lowing a repair, the technician should perform the
following steps:

Important:
Follow the steps below when you verify repairs on board
diagnostic systems. Failure to follow these steps could
result in unnecessary repairs.

1. Review and record the Failure Records for the

DTC which has been diagnosed.

2. Clear the DTC (S).
3. Operate the vehicle within conditions according to

customer complaint.

4. Monitor the Diagnostic Trouble Code (DTC) status

information for the specific DTC which has been di-
agnosed until the diagnostic test associated with
that DTC runs.

Isuzu N-Series. Manual - part 419