1999 HONDA CIVIC troubleshooting

Troubleshooting Tests
Testing for Voltage
When testing for voltage at a connector
without wire seals, you do not have to
seoarate the two halves of the connector.
Instead, probe the connector from the back.
Always check both sides of the connector
because dirty, corroded, and bent terminals
can cause problems (no electrical contact =
an open).
1 . Connect one lead of the test light to a
known good ground, or, if you're using a
digital volt ohmmeter (DVOM), place it in
the appropriate DC volts range, and
connect its negative lead to ground.
Connect the other lead of the test light or
DVOM to the point you want to check.
lf the test light glows, there is voltage
present. lf you're using a DVOM, note the
voltage reading. lt should be within one
volt of measured battery voltage.
A loss of more than one volt indicates
a problem.
NOTE: Always use a DVOM on high
impedance circuits. A test light may not
glow (even with baftery voltage present).
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Testing for Continuity
When testing for continuity at a connector
without wire seals, you do not have to
separate the two halves of the connector.
lnstead. Drobe the connector Jrom the back.
Always check both sides of the connector
because dirty, conoded, and bent terminals
can cause problems (no electrical contacl =
an open).
1. Disconnect the negative cable from the car
battery. lf you're using a DVOM, place it in
the lowest "OHMS" range.
2. Connect one lead of a self-powered test
light or DVOM to one end of the part of the
circuit vou want lo test.
Connect the other lead to the other end.
lf the self-powered test light glows, there is
continuity. lf you're using a DVOM, a low
reading or no reading (zero), means
good continuity.
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How To Use This Manual
Troubleshooting Tests
Testing for Voltage Drop
Wires, connectors, and switches are designed
to conduct current wilh a minimum loss of
voltage. A voltage drop of more than one volt
indicates a Droblem.
'1. Place the digital volVohmmeter (DVOM) in
the appropriate DC volts range. Connect
the positive lead to the end of the wire
(or to the connector or switch) closest to
the bafterv.
Connect the negative lead to the other
end of the wire (or the other side of the
connector or switch).
Turn on the components in the circuit.
The DVOM will show the difference
in voltage between the two points. A
difference, or drop, of more than one
volt indicates a oroblem. Check the
circuit for loose, dirty, or bent terminals.
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Testing lor a Short with a Test Light or DVOM
1. Remove the blown fuse and disconnect
the load.
2. Connect a test light or digital
oltr'ohmmeter
(DVOM), switched to the appropnare DC
volts range, across the tuse lerminals to
make sure voltage is present. You might
have to turn the ignition switch to ON:
check the schematic to see.
<-s80RT TOGFOUNO
Disconnecl lheload here.
Beginning near the luse box, wiggle the
harness. Continue this at convenient ooints
about six inches apart while watching the
test light or DVOM.
Where the test light goes off, or the DVOM
voltage drops to zero, there is a short to
ground in the wiring near that point.
NOTE: Always use a DVOM on high
impedance circuits. A test light may not
glow (even with battery voltage present).
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TEST LIGHTolDVOM

How To Use This Manual
Troubleshooting Tests (cont'd)
4. Turn on the short finder. This creates a
pulsing magnetic field around the wiring
between the fuse box and the short.
5. Beginning at the fuse box, slowly move
the short finder along the circuit wiring.
The meter will show current Dulses
through sheet metal and body trim. As
long as the meter is between the fuse and
lhe short, the needle will move with each
current pulse. Once you move the meter
past the point of the short, the needle will
stop moving. Check the wiring and
connectors in this area to locate the cause
of the short.
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- How the Gircuit Works
With the ignition switch in ON (ll) or START (lll),
battery voltage is supplied through fuse 15 and
the BLI(WHT and BLK/YEL wire to the vehicle
speed sensor (VSS). The sensor is grounded by
the BLK wire to G1 01 . The speedometer and
other control units in the circuit supply about 5
volts to the BLU/WHT wire. The vehicle soeed
sensor (VSS) intermittently grounds the
BLUMHT wire which generates a pulsed signal
in it. The number of pulses per minute
increases/decreasos with the soeed of the car.
Reter to th€ Service Manual (Section 23, Electrical)
tor specific tosts or troubleshooting procedures.
33-1

Gruise Control (cont'd)
- How the Circuit Works
The cruise control system uses mechanical and
electrical devices to maintain the car's sDeed at a
setting selected by the driver.
System Description
The cruise control unit receives command signals
from the crurse control main switch and the cruise
control SeVResume switch. With the ignition switch
in ON (ll) or START (lll), voltage is provided to the
cruise control main switch through fuse 14. When
you push the switch to ON, power is provided to the
cruise control unit and the brake switch.
The cruise control unit receives information about
operating conditions from the brake switch, the
vehicle speed sensor (VSS), and the clutch switch
(manual transmission) or the A,/T gear position
switch (automatic transmission). The cruise control
unit then sends signals to the cruise control actuator
which regulates the throttle position to maintain the
selected speed. The conlrol unit compares the
actual speed of the car to the selected speed. The
control unit then uses the result of that comoarison
to open or close the throttle.
The brake switch releases the system's control of
the throttle at the instant you press on the brake
pedal. The switch sends a signal to the control unit
by removing power from the normally closed brake
input (GRY wire), and providing power at the
normally open brake input (GRN/vVHT wire). The
control unit responds by allowing the throttle to
close. The clutch switch or the A,/T gear position
switch sends a "disengage" signal to the control unit
that also allows the throttle to close.
The cruise control system will set and automatically
maintain any speed above 25 mph (40 km/h). To set
it, make sure the main switch is on and the switch
indicator is on. Then, after reaching the desired
speed, press the SET switch. This sends a "set"
signal to the cruise control unit which, in turn,
controls the cruise control actuator to maintain the
set speed.
When you push the SET switch and the cruise
control system is on, the "cruise control" ON
indicator lights up.
34-4
(
You can cancel the cruise control system by
turning the main switch off . This removes power to
the control unit and erases the set speed from
memory. lf the system is disengaged temporarily
by the brake switch, or clutch switch, and the car's
speed is still above 25 mph, press the resume
switch: the car will automatically return to the
previously set speed.
For gradual acceleration without pressing the
accelerator pedal, push the RESUME switch and
hold it there. This will send an "acceleration" signal
to the control unit. When you release the switch, the
system will be reprogrammed for the new speed. To
slow the car down. oush the SET switch in and hold
it there. This sends a "deceleration" signal to the
control unit, causing the car to coast. When the
desired speed is reached, release the SET switch.
This reprograms the system tor the new speed.
Refer to the Service Manual (Section 23, Electrical)
tor specific tests or troubleshooting procedures.
(
a

- How the Circuit Works
The anti-lock brake system (ABS) prevents locking
of the wheels as a result of heavy braking and/or
poor lraction. A vehicle with locked wheels cannot
be steered. The anti-lock brake system controls the
application of the brakes, allowing the driver to
maintain control of the steering.
Under anti-lock conditions, the antilock brake
system (ABS) modulates the pressure of the brake
tluid to each brake caliper. This system is a four
channel system: the pressure at each caliper is
controlled independently of the pressure al any
other caliper. Whenever a wheel is likely to lock
dunng braking, the anti-lock brake system
modulates the brake oressure at that wheel. When
the brake pressure is reduced to the point where
there is no longer any possibility of wheel locking,
the system returns to the conventional braking
system mode of operation.
Battery voltage is applied at all times through fuse
63 to the ABS control unit. When the ignition switch
is in ON (ll), battery voltage is supplied to the
control unit through fuse 16. The control unit is case
grounded. Inputs are received from the brake switch
and the individual wheel sensors located at each
wheel. The ABS control unit uses these inputs to
control the modulator solenoid unit. The solenoids
adjust the hydraulic pressure applied to each
calioer.
The ABS control unit has a self-diagnosis function.
When the control unit detects a fault, it turns on the"ABS" indicator and disables the anti-lock brake
system. lf the fault is not in the conventional braking
system, the brakes will continue to operate normally
but without the anti-lock feature.
Refer to the Service Manual (Section '19,
Anti-Lock Brake System) for specific tests or
troubleshooting procedures.
44-3

- How the Circuit Works
'96198 Models
The air delivery system directs the flow of air used
by the heater and air conditioner systems.
Mode Selection
Mode selection is controlled by the mode switches
in the heater control panel and the mode control
motor. When you select a specific mode, voltage is
applied through the dimming circuit to the LED,
which comes on, indicating the mode selected.
Ground is orovided to the mode control motor
though that mode switch. The motor then runs until
the air control door reaches the proper position.
Fresh/Recirculation 56lection
When you press the fresh or recirculation button, a
ground signal is sent from the heater control panel
to the recirculation control motor. The motor then
runs until the recirculation door reaches the proper
position. Battery voltage is also applied through the
dimming circuit to the corresponding LED, and the
LED comes on.
Refer to the Service Manual (Section 21, Heater) for
specitic tests or troubleshooting proc€dures.
'99J00 Models
The heater control panel receives battery voltage at
all times through fuse 47. With the ignition switch in
ON (ll), voltage is supplied to the heater control
panel through fuse 17. The control panel is
grounded at G402.
The heater control panel controls the air delivery
motors, and supplies a 5 VDC reterence voltage to
the air mixture control motor.
The air mixture and mode control motors each
receive inputs trom the heater control panel. The air
mix motor regulates the mixture of cold and hot air
by varying the position of the heater-evaporator doot
The mode control motor controls the direction and
volume of outlet air. The air flow can be directed to
the dashboard vents or the corner vents.
Both the air mixture control molor and mode control
motor are grounded by the h€aler control panel.
The recirculation control motor receives battery
voltage through fuso 17 when the ignition swilch is
in ON (ll). lt regulates the position of the fresh/recirc
door, and is controlled by two position inputs from
the heater control panel ("Recirc" and "Fresh").
Refer to the Service Manual (Section 21, Heater) tor
specific tests or troubleshooting procedures.
61-3

- How the Circuit Works
Battery voltage is supplied through tuse 56 to the
A,/C compressor clutch r€lay contacts at all times.
With the ignition switch in ON (ll), vollage is applied
to the coil of the A,/C compressor clutch relay
through fuse 17. When you push the A,/C switch
ON, and the heater fan switch is in position | , 2, 3,
or 4, a "ground" input is provided to the engine
control module (ECM) or powertrain control module
(PCM) through the l'lC thermostat and the l'lC
pressure switch.
The A,/C compressor clutch relay is grounded by the
engine control module (ECM) or powertrain control
module (PCM). When energized, the A'lC
compressor clutch relay allows battery voltage to
turn on the A,/C comDressor clutch.
The A,/C ON indicator light comes on when the A,/C
system is requested.
A,/C Thermostat
The A'lC thermostat is located on the evaoorator
housing. The A,/C thermostat turns off the A,/C
compressor clutch if the temperature at the
evaporator goes below 3'C (37'F). This prevents
condensation from freezing on the evaporator fins
and blocking the air delivery into the passenger
compartment. The blower motor will keep running
when the sensor turns off the comDressor.
A,/C Pressure Switch
The fuC oressure switch is located in the condenser
outlet line where refrigerant is in a high
temperature/high pressure liquid state. The switch
will sense abnormally high or low pressure, and
open the circuit. This removes ground, and the
compressor will stop running.
Thermal Protectot
The thermal protector, located on the A,/C
compressor, opens and turns the compressor off if it
senses high temperature. Once the compressor
cools, the switch will close and the compressor will
begin running again.
Refer to the Service Manual (Section 22,
Air Conditioning) for specific tests or
troubleshooting procedures.
62-3