Infiniti M35/M45 Y50. Manual - part 794

SERVICE INFORMATION FOR ELECTRICAL INCIDENT

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Freezing

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Water intrusion

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Electrical load

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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.

CONNECTORS & HARNESS
Determine which connectors and wiring harness would affect the electrical system you are inspecting. Gently
shake each connector and harness while monitoring the system 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 corrosion. It is a good idea to disconnect, inspect and clean the
terminals on related connectors in the system.

SENSORS & RELAYS
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:

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Connectors not fully seated.

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Wiring harness not long enough and is being stressed due to engine vibrations or rocking.

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Wires laying across brackets or moving components.

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Loose, dirty or corroded ground wires.

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Wires routed too close to hot components.

To inspect components under the hood, start by verifying 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 previously 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.

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SERVICE INFORMATION FOR ELECTRICAL INCIDENT

UNDER SEATING AREAS
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 seating 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.
Do not heat components above 60

°

C (140

°

F). If incident occurs

while heating the unit, either replace or properly insulate the compo-
nent.

Freezing 

The customer may indicate the incident goes away after the car
warms up (winter time). The cause could be related to water freezing
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 outside
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.
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.

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SERVICE INFORMATION FOR ELECTRICAL INCIDENT

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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.

CIRCUIT INSPECTION 
Introduction 

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 testing electrical components. Gently shake the wiring har-
ness or electrical component to do this.

NOTE:
Refer to “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 circuit. 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 circuits, please refer to the previous schematic.

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Disconnect the battery negative cable.

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Start at one end of the circuit and work your way to the other end. (At the fuse block in this example)

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Connect one probe of the DMM to the fuse block terminal on the load side.

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Connect the other probe to the fuse block (power) side of SW1. Little or no resistance will indicate that
portion 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)

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Connect the probes between SW1 and the relay. Little or no resistance will indicate that portion of the cir-
cuit has good continuity. If there were an open in the circuit, the DMM would indicate an over limit or infi-
nite resistance condition. (point B)

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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 circuit, the DMM would indicate an over limit or
infinite resistance condition. (point C)

Any circuit can be diagnosed using the approach in the previous example.

OPEN

A circuit is open when there is no continuity through a section of the circuit.

SHORT

There are two types of shorts.

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SHORT CIRCUIT

When a circuit contacts another circuit and causes the normal resistance to 
change.

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SHORT TO GROUND

When a circuit contacts a ground source and grounds the circuit.

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SERVICE INFORMATION FOR ELECTRICAL INCIDENT

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 methodically checking the system for the presence of voltage.
This is done by switching the DMM to the voltage function.

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Connect one probe of the DMM to a known good ground.

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Begin probing at one end of the circuit and work your way to the other end.

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With SW1 open, probe at SW1 to check for voltage.
voltage; open is further down the circuit than SW1.
no voltage; open is between fuse block and SW1 (point A).

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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).

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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

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Disconnect the battery negative cable and remove the blown fuse.

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Disconnect all loads (SW1 open, relay disconnected and solenoid disconnected) powered through the
fuse.

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Connect one probe of the DMM to the load side of the fuse terminal. Connect the other probe to a known
good ground.

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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.

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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.

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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

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Remove the blown fuse and disconnect all loads (i.e. SW1 open, relay disconnected and solenoid discon-
nected) powered through the fuse.

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Turn the ignition key to the ON or START position. Verify battery voltage at the battery + side of the fuse
terminal (one lead on the battery + terminal side of the fuse block and one lead on a known good ground).

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With SW1 open and the DMM leads across both fuse terminals, check for voltage.
voltage; short is between fuse block and SW1 (point A).

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