1995 NISSAN ALMERA N15 Service Manual

•SHORT CIRCUIT
• SHORT TOGROUND

HOW
TOPERFORM EFFICIENT DIAGNOSIS FORANELECTRICAL INCIDENT
Circuit Inspection

•

A circuit isopen when thereisno continuity throughasection ofthe circuit.
There aretwo types ofshorts.
Whenacircuit contacts anothercircuitandcauses the
normal resistance tochange.
When acircuit contacts aground sourceandgrounds the
circuit.

INTRODUCTION

In general, testingelectrical circuitsisan easy taskifitis approached inalogical andorganized method.
Before beginning itis important tohave allavailable information onthe system tobe tested. Also,get
a thorough understanding ofsystem operation. Thenyouwillbeable touse theappropriate equipment
and follow thecorrect testprocedure.
You may have tosimulate vehiclevibrations whiletesting electrical components.
Gentlyshake
thewir-
ing harness orelectrical component todo this.

OPEN

SHORT

TESTING FOR"OPENS" INTHE CIRCUIT

[YJ
(Voltage check)
Before
youbegin todiagnose andtestthesystem, youshould roughsketch aschematic ofthe system.
This willhelp youtologically walkthrough thediagnosis process.Drawingthesketch willalso reinforce
your working knowledge ofthe system.

Inspection foropens
-+
DMM

Ll
~SE. ~L9~K

I
I

I __-,----

B + SIDE
I
OPEN

I I
A

L
-.J

[ill
DMM
SGI846
Continuity checkmethod

The continuity checkisused tofind anopen inthe circuit. TheDigital Multimeter (DMM)setonthe
resistance functionwillindicate anopen circuit asover limit(OL,nobeep toneorno ohms symbol). Make
sure toalways startwiththeDMM atthe highest resistance level.
To help inunderstanding thediagnosis ofopen circuits pleaserefertothe schematic above.
1. Disconnect thebattery negative cable.
2. Start atone end ofthe circuit andwork yourwaytothe.other end.(Atthe fuse block inthis exam-
ple)
3. Connect oneprobe ofthe DMM tothe fuse block terminal onthe load side.
4. Connect theother probe tothe fuse block (power) sideofSW1. Littleorno resistance willindicate
that portion ofthe circuit hasgood continuity. Ifthere wereanopen inthe circuit, theDMM would
indicate anover limitorinfinite resistance condition.(pointA)
5. Connect theprobes between SW1andtherelay. Littleorno resistance willindicate thatportion of
the circuit hasgood continuity. Ifthere wereanopen inthe circuit, theDMM would indicate anover
limit orinfinite resistance condition.(pointB)
6. Connect theprobes between therelay andthesolenoid. Littleorno resistance willindicate thatpor-
tion ofthe circuit hasgood continuity. Ifthere wereanopen inthe circuit, theDMM would indicate
an over limitorinfinite resistance condition.(pointC)
Any circuit canbediagnosed usingtheapproach inthe above example.

GI-23

HOWTOPERFORM EFFICIENT DIAGNOSIS FORANELECTRICAL INCIDENT
Circuit Inspection (Cont'd)
Voltage checkmethod

To help inunderstanding thediagnosis ofopen circuits pleaserefertothe previous schematic.
In any powered circuit,anopen canbefound bymethodically checkingthesystem forthe presence of
voltage. Thisisdone byswitching theDMM tothe voltage function.
1. Connect oneprobe ofthe DMM toaknown goodground.
2. Begin probing atone endofthe circuit andwork yourwaytothe other end.
3. With SW1open, probe atSW1 tocheck forvoltage.
voltage; openisfurther downthecircuit thanSW1.
no voltage; openisbetween fuseblock andSW1 (point A).
4. Close SW1andprobe atrelay.
voltage; openisfurther downthecircuit thantherelay.
no voltage; openisbetween SW1andrelay (point B).
5. Close therelay andprobe atthe solenoid.
voltage; openisfurther downthecircuit thanthesolenoid.
no voltage; openisbetween relayandsolenoid (pointC).
Any powered circuitcanbediagnosed usingtheapproach inthe above example.

SGI847
RELAY
~I SH~
SW2
c

1

(Resistance
check)

IGN "ON"

t
OR "S~:R.T~ '::~SEBLOCK

I I '-
SWl

I I
-=

B+SIOEl~~-:-~
~r-o~

SHORT SHORT

[YJ
DMMA B

+ -
(Voltage check)
TESTING
FOR"SHORTS" INTHE CIRCUIT

To simplify thediscussion ofshorts inthe system pleaserefertothe schematic below.

Inspection forshorts
Resistance checkmethod

1. Disconnect thebattery negative cableandremove theblown fuse.
2. Disconnect allloads (SW1open, relaydisconnected andsolenoid disconnected) poweredthroughthe
fuse.
3. Connect oneprobe ofthe ohmmeter tothe load sideofthe fuse terminal. Connecttheother probe
to aknown goodground.
4. With SW1open, check forcontinuity.
continuity; shortisbetween fuseterminal andSW1 (point A).
no continuity; shortisfurther downthecircuit thanSW1.
5. Close SW1anddisconnect therelay. Putprobes atthe load side offuse terminal andaknown good
ground. Then,check forcontinuity.
continuity; shortisbetween SW1andtherelay (point B),
no continuity; shortisfurther downthecircuit thantherelay.
6. Close SW1andjump therelay contacts withjumper wire.Putprobes atthe load sideoffuse termi-
nal and aknown goodground. Then,check forcontinuity.
continuity; shortisbetween relayandsolenoid (pointC).
no continuity; checksolenoid, retracesteps.

GI-24

HOWTOPERFORM EFFICIENT DIAGNOSIS FORANELECTRICAL INCIDENT
Circuit Inspection (Cont'd)
Voltage checkmethod

1. Remove theblown fuseanddisconnect allloads (i.e.SW1 open, relaydisconnected andsolenoid •
disconnected) poweredthroughthefuse.
2. Turn theignition keytothe ONorSTART position. Verifybattery voltage atthe B
+
side ofthe fuse
terminal (oneleadonthe B
+
terminal sideofthe fuse block andone lead onaknown goodground).
3. With SW1 open andtheDMM leads across bothfuseterminals, checkforvoltage.
voltage; shortisbetween fuseblock andSW1 (point A).
no voltage; shortisfurther downthecircuit thanSW1.
4. With SW1 closed, relayandsolenoid disconnected andtheDMM leadsacross bothfuseterminals,
check forvoltage.
voltage; shortisbetween SW1andtherelay (point B).
no voltage; shortisfurther downthecircuit thantherelay.
5. With SW1 closed, relaycontacts jumpedwithfused jumper wirecheck forvoltage.
voltage; shortisdown thecircuit ofthe relay orbetween therelay andthedisconnected sole-
noid (point C).
no voltage; retracestepsandcheck power tofuse block.

GROUND INSPECTION

Ground connections arevery important tothe proper operation ofelectrical andelectronic circuits.
Ground connections areoften exposed tomoisture, dirtand other corrosive elements. Thecorrosion
(rust) canbecome anunwanted resistance. Thisunwanted resistance canchange theway acircuit
works. Electronically controlledcircuitsarevery sensitive toproper grounding. Aloose orcorroded groundcan
drastically affectanelectronically controlledcircuit.Apoor orcorroded groundcaneasily affectthecir-
cuit. Even when theground connection looksclean, therecanbeathin film ofrust onthe surface.
When inspecting aground connection followtheserules:
1. Remove theground boltscrew orclip.
2. Inspect allmating surfaces fortarnish, dirt,rust, etc.
3. Clean asrequired toassure goodcontact.
4. Reinstall boltorscrew securely.
5. Inspect for"add-on" accessories whichmaybeinterfering withtheground circuit.
6. Ifseveral wiresarecrimped intoone ground eyeletterminal, checkforproper crimps. Makesure
all ofthe wires areclean, securely fastened andproviding agood ground path.Ifmultiple wiresare
cased inone eyelet makesurenoground wireshaveexcess wireinsulation.

Ground Inspection

•
Removeboll(screw).
•

GI-25
Inspect
matingsurfaces
for tarnish. dirt.rust. etc.
Clean asrequired to
assure goodcontact.
•

Reinstallbolt(screw)
securely.

SGI853

HOWTOPERFORM EFFICIENT DIAGNOSIS FORANELECTRICAL INCIDENT
Circuit Inspection (Cont'd)
VOLTAGE DROPTESTS

Voltage droptests areoften usedtofind components orcircuits whichhaveexcessive resistance. A
voltage dropinacircuit iscaused byaresistance
whenthecircuit isin operation.

Check thewire inthe illustration. Whenmeasuring resistancewithohmmeter, contactbyasingle strand
of wire willgive reading of0ohms. Thiswould indicate agood circuit. Whenthecircuit operates, this
single strand ofwire isnot able tocarry thecurrent. Thesingle strand willhave ahigh resistance tothe
current. Thiswillbepicked upasaslight voltage drop.
Unwanted resistance canbecaused bymany situations asfollows:
Undersized wiring(single strandexample)
Corrosion onswitch contacts
Loose wireconnections orsplices.

If
repairs areneeded alwaysusewire thatisof the same orlarger gauge.

Measuring voltagedrop-Accumulated method

1. Connect thevoltmeter acrosstheconnector orpart ofthe circuit youwant tocheck. Thepositive lead
of the voltmeter shouldbecloser topower andthenegative leadcloser toground.
2. Operate thecircuit.
3. The voltmeter willindicate howmany voltsarebeing usedto"push" current through thatpart ofthe
circuit.

Note inthe illustration thatthere isan excessive 4.1volt drop between thebattery andthebulb.
Symptom: Dimbulb orno operation
Switch Connectionwith
high resistance

l ;

--

------------------~

--
\

~~~~ I

-, OVI

11.9V:
'I

I
Load)

--

12V
DMM
Battery
Ground

o

(zero) ohm
resistance
between switch
and bulb

t
•
__
Ground
SGI848
Measuring voltagedrop-Step bystep

The step bystep method ismost useful forisolating excessive dropsinlow voltage systems (suchas
those in"Computer ControlledSystems").
Circuits inthe "Computer ControlledSystem"operateonvery lowamperage.
The (Computer Controlled) systemoperations canbeadversely affectedbyany variation inresistance
in the system. Suchresistance variationmaybecaused bypoor connection, improperinstallation,
improper wiregauge orcorrosion.
The step bystep voltage droptestcan identify acomponent orwire withtoomuch resistance.

GI-26

HOWTOPERFORM EFFICIENT DIAGNOSIS FORANELECTRICAL INCIDENT
Circuit Inspection (Cont'd)

1. Connect thevoltmeter asshown, starting atthe battery and •
working yourwayaround thecircuit.
2. An unusually largevoltage dropwillindicate acomponent or
wire thatneeds tobe repaired. Asyou canseetheillustration
above, thepoor connection causesa4 volt drop.
The chart thatfollows illustrates somemaximum allowablevoltagedrops.Thesevalues aregiven asaguideline, theexact valueforeach
component mayvary.

COMPONENT

Wire
Ground Connections
Switch Contacts
VOLTAGE
DROP

negligible <.001volts
Approx.
0,1
volts
Approx. 0.3volts

GI-27 SGI854

HOWTOPERFORM EFFICIENT DIAGNOSIS FORANELECTRICAL INCIDENT
Circuit Inspection (Cont'd)
Relationship betweenopen/short (highresistance) circuitandtheECM pincontrol

System Description: Whentheswitch isON, theECM lights upthe lamp.

j

Case
1

Battery
'-----v--J

Short: FUSEblows.
Open: Inoperative lamp TERMINAL:
1
Monitoring
of the switch
operation (ON/OFF)

\~--~y

Short: FUSEblows
when switch isON.
Open: Inoperative lampECM
2
TERMINAL:
2
Power supply
to light up
the lamp

'"-----v~----)
Short
&
Open:
Inoperative lampLamo

~

Short: Noproblem
Open: Inoperative lamp
High resistance:
(Single strand) Seebelow.'

Input-output voltagechart

Pin Item
Condition Voltage
In1:ase ofhigh resistance
No. value[V]
suchassingle strand [V]
*

1
Switch
Switch Battery
Lowerthanbattery voltage
ON voltage Approx.8(Example)
OFF Approx.O Approx.O

2
Lamp
Switch Battery
Approx.O
ON voltage
(Inoperativelamp)
OFF Approx.O Approx.O
The voltage valueisbased onthe body ground.
: If high resistance existsinthe switch sidecircuit (caused byasingle strand), terminal 1does notdetect battery voltage. ECM
does notdetect theswitch isON even ifthe switch doesturnON.Therefore. theECM does notsupply powertolight upthe lamp.

Case 2

Lamp
Battery TERMINAL:
1
Ground control
to light upthe lamp
2TERMINAL:
2
Monitoring
of the switch
operation (ON/OFF) Switch

o

)

'---v---J

Short: FUSEblows.
Open: Inoperative lamp

Input-output voltagechart
\.----v

Short: LampstaysON.
Open: Inoperative lamp
ECM

\~--~v~--_.J

Short: LampstaysON.
(Same asthe switch ON)
Open: Inoperative lamp
High resistance: Seebelow.
(Single strand)'
"---y-----.J

Short: Noproblem
Open: Inoperative lamp
Pin Item Condition Voltage
Incase ofhigh resistance
No. value[V]
suchassingle strand [V]
*

1
Lamp
Switch
Approx.OBatteryvoltage
ON (Inoperat ivelamp)
OFF Battery
Batteryvoltage
voltage

2
Switch Switch Approx.OHigherthan0
ON Approx.4(Example)
OFF Approx.5
Approx.5
The voltage valueisbased onthe body ground.
• :If high resis1ance existsinthe switch sidecircuit (caused byasingle strand), terminal 2does notdetect approx. OV.ECM does
not detect theswitch isON even ifthe switch doesturnON.Therefore, theECM does notcontrol ground tolight upthe lamp.

SG1849-A

GI-28

HOWTOFOLLOW FLOWCHART INTROUBLE DIAGNOSES
NOTICE

The flow chart indicates workprocedures requiredtodiagnose
problems effectively. Observethefollowing instructions before
diagnosing.
1) Use theflow chart afterlocating probable causesofaprob-
lem following the"Preliminary Check",the"Symptom
Chart" orthe "Work Flow".
2) After repairs, re-check thattheproblem hasbeen com-
pletely eliminated.
3) Refer toComponent PartsandHarness Connector Location
for the Systems described ineach section foridentificationl
location ofcomponents andharness connectors.
4) Refer tothe Circuit Diagram forQuick Pinpoint Check.
If you must check circuit continuity betweenharnesscon-
nectors inmore detail, suchaswhen asub-harness isused,
refer toWiring Diagram ineach individual sectionandHar-
ness Layout inEL section foridentification ofharness con-
nectors.
5) When checking circuitcontinuity, ignitionswitchshould be

"OFF" .

6) Before checking voltageatconnectors, checkbattery volt-
age.
7) After accomplishing theDiagnostic Procedures andElectri-
cal Components Inspection,makesurethatallharness con-
nectors arereconnected asthey were.
•

Example
m ..
-=-=~-----------~

~

~i5
[YJ

SGI561
~

OISCONNECT

18
SGI562
INSPECTION
START
CHECK POWER SUPPLY.
1) Turn ignition switch"ON".
2) Check voltage between terminal
@

and ground.

~Ba"ery voltageshouldexist.

OK

2

Ii)
CHECK GROUND CIRCUIT.
1) Turn ignition switch"OFF"
2) Disconnect camshaftpositionsensor
harness connector.
3) Check resistance betweenterminal

@
and ground.

Resistance: Approximately
on

OK
GI-29 NG
Check
thefollowing
items. 1) Harness continuity
between camshaft
position sensorand
battery
2) ECCS relay-1
3) "SR" fusible link
4) Power source for

ECM

5) Ignition switch
Check thefollowing
items. 1) Harness continuity
between camshaft
position sensorand
ground
2) Ground circuitfor

ECM

SG1800-C

HOWTOFOLLOW FLOWCHART INTROUBLE DIAGNOSES
HOW TOFOllOW THISFLOW CHART

OJ
Work anddiagnostic procedure

Start todiagnose aproblem usingprocedures indicatedin
enclosed blocks,asshown inthe following example.

CHECK POWER SUPPLY.
1) Turn ignition switch"ON".
2) Check voltage between terminal
@

and ground.

Battery voltage shouldexist.
-+-

Check itembeing per-
formed.

} Procedure, stepsormea-
surement results

[2]
Measurement results

Required resultsareindicated inbold type inthe corre-
. sponding block,asshown below:
These havethefollowing meanings:

Battery voltage -11 .14V orapproximately 12V
Voltage: Approximately OV-Less than1V
~ Cross reference ofwork symbols inthe text and
illustrations

Illustrations areprovided asvisual aidsforwork proce-
dures. Forexample, symbol
m
indicated inthe leftupper
portion ofeach illustration corresponds withthesymbol in
the flow chart foreasy identification. Moreprecisely, the
procedure underthe"CHECK POWERSUPPLY" outlined
previously isindicated byan illustration
m.

[4J
Symbols usedinillustrations

Symbols includedinillustrations refertomeasurements or
procedures. Beforediagnosing aproblem, familiarize your-
self with each symbol.

Direction mark

Refer to"CONNECTOR SYMBOLS"onGI-13.

GI-30