
Do not attempt to top up the fuel tank after the fuel pump nozzle
shuts off automatically. Continued refueling may cause fuel
overflow, resulting in fuel spray and possibly a fire.
WARNING:
To prevent ECM from storing the diagnostic trouble codes, do
not carelessly disconnect the harness connectors which are
related to the engine control system and TCM (Transmission
Control Module) system. The connectors should be discon-
nected only when working according to the WORK FLOW of
TROUBLE DIAGNOSES in EC and AT sections.
SGI787
PRECAUTIONS FOR MULTIPORT FUEL INJECTION
SYSTEM OR ENGINE CONTROL SYSTEM
NLGI0001S04+Before connecting or disconnecting any harness connector for
the multiport fuel injection system or ECM:
Turn ignition switch to“OFF”position.
Disconnect negative battery terminal.
Otherwise, there may be damage to ECM.
+Before disconnecting pressurized fuel line from fuel pump to
injectors, be sure to release fuel pressure.
+Be careful not to jar components such as ECM and mass air
flow sensor.
PRECAUTIONS FOR THREE WAY CATALYSTNLGI0001S05If a large amount of unburned fuel flows into the catalyst, the cata-
lyst temperature will be excessively high. To prevent this, follow the
instructions below:
+Use unleaded gasoline only. Leaded gasoline will seriously
damage the three way catalyst.
+When checking for ignition spark or measuring engine
compression, make tests quickly and only when necessary.
+Do not run engine when the fuel tank level is low, otherwise the
engine may misfire, causing damage to the catalyst.
Do not place the vehicle on flammable material. Keep flammable
material off the exhaust pipe and the three way catalyst.
SMA019D
PRECAUTIONS FOR HOSESNLGI0001S06Hose Removal and InstallationNLGI0001S0601+To prevent damage to rubber hose, do not pry off rubber hose
with tapered tool or screwdriver.
PRECAUTIONS
Precautions (Cont’d)
GI-6

TESTING FOR“OPENS”IN THE CIRCUITNLGI0005S0302Before you begin to diagnose and test the system, you should
rough sketch a schematic of the system. This will help you to logi-
cally walk through the diagnoses process. Drawing the sketch will
also reinforce your working knowledge of the system.
SGI846
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 diagnoses of open circuits please
refer to the schematic above.
1) Disconnect the battery negative cable.
2) Start at one end of the circuit and work your way to the other
end. (At the fuse block in this example)
3) Connect one probe of the DMM to the fuse block terminal on
the load side.
4) 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)
5) Connect the probes between SW1 and the relay. Little or no
resistance will indicate that portion of the circuit has good con-
tinuity. If there were an open in the circuit, the DMM would
indicate an over limit or infinite resistance condition. (point B)
6) 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 above
example.
Voltage Check Method
To help in understanding the diagnoses 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.
1) Connect one probe of the DMM to a known good ground.
2) Begin probing at one end of the circuit and work your way to
the other end.
3) 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).
4) Close SW1 and probe at relay.
HOW TO PERFORM EFFICIENT DIAGNOSES FOR AN ELECTRICAL INCIDENT
Circuit Inspection (Cont’d)
GI-25

voltage; open is further down the circuit than the relay.
no voltage; open is between SW1 and relay (point B).
5) 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
above example.
TESTING FOR“SHORTS”IN THE CIRCUITNLGI0005S0303To simplify the discussion of shorts in the system please refer to
the schematic below.
SGI847
Resistance Check Method
1) Disconnect the battery negative cable and remove the blown
fuse.
2) Disconnect all loads (SW1 open, relay disconnected and sole-
noid disconnected) powered through the fuse.
3) Connect one probe of the ohmmeter to the load side of the fuse
terminal. Connect the other probe to a known good ground.
4) 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.
5) 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.
6) 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
1) Remove the blown fuse and disconnect all loads (i.e. SW1
open, relay disconnected and solenoid disconnected) powered
through the fuse.
2) Turn the ignition key to the ON or START position. Verify bat-
tery voltage at the B + side of the fuse terminal (one lead on
the B + terminal side of the fuse block and one lead on a known
good ground).
3) With SW1 open and the DMM leads across both fuse
terminals, check for voltage.
voltage; short is between fuse block and SW1 (point A).
no voltage; short is further down the circuit than SW1.
4) With SW1 closed, relay and solenoid disconnected and the
DMM leads across both fuse terminals, check for voltage.
voltage; short is between SW1 and the relay (point B).
HOW TO PERFORM EFFICIENT DIAGNOSES FOR AN ELECTRICAL INCIDENT
Circuit Inspection (Cont’d)
GI-26

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
1) Connect the voltmeter across the connector or part of the cir-
cuit 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 circuit.
Note in the illustration that there is an excessive 4.1 volt drop
between the battery and the bulb.
SGI974
Measuring Voltage Drop—Step by Step
The step by step method is most useful for isolating excessive
drops in low voltage systems (such as those in“Computer Con-
trolled 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 resis-
tance 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.
HOW TO PERFORM EFFICIENT DIAGNOSES FOR AN ELECTRICAL INCIDENT
Circuit Inspection (Cont’d)
GI-28

SGI854
CONTROL UNIT CIRCUIT TESTNLGI0005S0306System Description: When the switch is ON, the control unit lights
up the lamp.
MGI034A
Input-output voltage chart
Pin No. Item ConditionVoltage
value VIn case of high resistance such as single strand V *
1 Switch Switch ON Battery voltage Lower than battery voltage Approx. 8 (Example)
Switch OFF Approx. 0 Approx. 0
2 Lamp Switch ON Battery voltage Approx. 0 (Inoperative lamp)
Switch OFF Approx. 0 Approx. 0
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.
HOW TO PERFORM EFFICIENT DIAGNOSES FOR AN ELECTRICAL INCIDENT
Circuit Inspection (Cont’d)
GI-29

MGI035A
Input-output voltage chart
Pin No. Item ConditionVoltage
value VIn case of high resistance such as single strand V *
1 Lamp Switch ON Approx. 0 Battery voltage (Inoperative lamp)
Switch OFF Battery voltage Battery voltage
2 Switch Switch ON Approx. 0 Higher than 0 Approx. 4 (Example)
Switch OFF Approx. 5 Approx. 5
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 turns ON. Therefore, the control unit does not control ground to light up the lamp.
HOW TO PERFORM EFFICIENT DIAGNOSES FOR AN ELECTRICAL INCIDENT
Circuit Inspection (Cont’d)
GI-30

NLGI0006
NOTICE:
Trouble diagnoses indicate work procedures required to diagnose
problems effectively. Observe the following instructions before
diagnosing.
1)Before performing trouble diagnoses, read the“Prelimi-
nary 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
identification/location of components and harness con-
nectors.
4)Refer to the Circuit Diagram for quick pinpoint check.
If you need to check circuit continuity between harness
connectors 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 identification 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.
HOW TO FOLLOW TROUBLE DIAGNOSES
GI-31

How to Follow Test Groups in Trouble
Diagnoses
NLGI0006S01
SGI975
1)Work and diagnostic procedure
Start to diagnose a problem using procedures indicated in
enclosed test groups.
2)Questions and required results
Questions and required results are indicated in bold type in test
group.
The meaning of are as follows:
a. Battery voltage→11 - 14V or approximately 12V
b. Voltage: Approximately 0V→Less than 1V
3)Symbol used in illustration
Symbols included in illustrations refer to measurements or pro-
cedures. Before diagnosing a problem, familiarize yourself with
each symbol. Refer to“CONNECTOR SYMBOLS”(GI-15) and
“Key to Symbols Signifying Measurements or Procedures”(GI-
33).
4)Action items
Next action for each test group is indicated based on result of
each question. Test group number is shown in the left upper
portion of each test group.
HOW TO FOLLOW TROUBLE DIAGNOSES
How to Follow Test Groups in Trouble Diagnoses
GI-32