1998 NISSAN PATROL wiring

VOLTAGE DROP TESTS
Voltage drop tests are often used to ®nd components or circuits which have excessive resistance. A voltage
drop in a circuit is caused by a resistancewhen the circuit is in operation.
Check the wire in the illustration. When measuring resistance with ohmmeter, 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 Ð Accumulated method
1. Connect the voltmeter across the connector or part of the circuit you want to check. The positive lead of
the voltmeter should be closer to power and the negative lead closer to ground.
2. Operate the circuit.
3. The voltmeter will indicate how many volts are being used to ``push'' current through that part of the cir-
cuit.
Note in the illustration that there is an excessive 4.1 volt drop between the battery and the bulb.
Measuring voltage drop Ð Step 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.
SGI974
HOW TO PERFORM EFFICIENT DIAGNOSIS FOR AN ELECTRICAL INCIDENT
Circuit Inspection (Cont'd)
GI-27

NOTICE:
The ¯ow chart indicates work procedures required to diagnose
problems effectively. Observe the following instructions before
diagnosing.
1) Use the ¯ow chart after locating probable causes of a prob-
lem following the ``Preliminary Check'', the ``Symptom
Chart'' or the ``Work Flow''.
2) After repairs, re-check that the problem has been com-
pletely eliminated.
3) Refer to Component Parts and Harness Connector Loca-
tion for the Systems described in each section for
identi®cation/location of components and harness con-
nectors.
4) Refer to the Circuit Diagram for Quick Pinpoint Check.
If you must check circuit continuity between harness con-
nectors in more detail, such as when a sub-harness is
used, refer to Wiring Diagram in each individual section
and Harness Layout in EL section for identi®cation of har-
ness connectors.
5) When checking circuit continuity, ignition switch should
be ``OFF''.
6) Before checking voltage at connectors, check battery volt-
age.
7) After accomplishing the Diagnostic Procedures and Elec-
trical Components Inspection, make sure that all harness
connectors are reconnected as they were.
Example
AGI056
HOW TO FOLLOW FLOW CHART IN TROUBLE DIAGNOSES
GI-30

Loading Procedure
CONSULT Data Link Connector (DLC) Circuit
INSPECTION PROCEDURE
If the CONSULT cannot diagnose the system properly, check the following items.
Symptom Check item
CONSULT cannot access
any system.+CONSULT DLC power supply circuit (Terminal 7) and ground circuit (Terminal 8)
(For detailed circuit, refer to ``MIL & Data Link Connectors Wiring Diagram'' in EC section.)
+CONSULT DDL cable
CONSULT cannot access
individual system. (Other sys-
tems can be accessed.)+CONSULT program card (Check the appropriate CONSULT program card for the system. Refer
to GI-33.)
+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 DLC
(For detailed circuit, refer to wiring diagram for each system.)
SGI983
SGI984
CONSULT CHECKING SYSTEM
GI-34