1999 HONDA CIVIC troubleshooting

- How the Circuit Works
Radiator Fan
Voltage is provided at all times to the radiator fan
relay (contacts) through fuse 57. With the ignition
swilch in ON (ll), voltage is provided to the coil of
the relay through luse 17.
The radiator tan relay can be grounded through
either the engine coolant temperature switch or the
engine control module (ECM) or powertrain control
module (PCM).
The engine coolant temperature switch grounds
the radiator fan relay (coil) when the engine
coolant temperature exceeds 199'F (83'C). The
switch opens when coolanl temperature
decreases 3'- 8'C.
Condenser Fan
Voltage is provided at all times to the condenser fan
relay (contacts) through fuse 56. With the ignition
switch in ON (ll), voltage is provided to the coil of
the relay through fuse 17. When you push the A'lC
switch and put the heater fan switch in 1, 2,3, o( 4
position, the ly'C thermostat comes on, the
condenser fan relay energizes, and the condenser
fan motor runs.
A,/C Thermostat
The A,/C thermostat is located on the evaporator
housing. The A,/C thermostat tums 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. lf the temperature goes below 3'C
(37"F) tuming off the Ay'C thermostat, ground will be
removed from the condenser fan relay. This will
deenergize the relay and remove voltage from the
condenser fan motor causing the fan to stop running.
Reter to the Service Manual (Section 23, Eleckical)
for specific tests or troubleshooting procedures.
63-3

Rear Window Defogger
- How the Circuit Works
'96198 Models
Voltage is applied at all limes through tuse 50 to the
rear window detogger relay (contacts). With the
ignition switch in ON (ll), voltage is applied through
tuse 16 to the rear window defogger switch.
When you turn the switch ON, voltage is applied to
the defogger timer circuit. The timer circuit supplies
voltage to the rear window defogger relay (coil). The
relay energizes and supplies voltage to the rear
window defogger. The defogger grid then heats the
rear window to remove any condensation from the
glass.
The defogger timer circuit will automatically turn off
the rear window defogger after about 25 minutes.
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
'99100 Models
Voltage is applied at all times through fuse 50 to the
rear window delogger relay (contacts). With lhe
ignition switch in ON (ll), voltage is applied through
fuse 16 to the heater control oanel.
When you turn the rear window defogger switch
ON, a signal is sent to lhe defogger timer circuit
built-into the heater control oanel. The timer circuit
supplies voltage to the rear window defogger relay
(coil). The relay energizes and supplies voltage to
the rear window defogger. The defogger grid then
heats the rear window to remove anv condensation
from the glass.
The defogger timer circuit will automatically turn otf
the rear window defogger after about 25 minutes.
Refer to the Seryice Manual (Section 23, Electrical)
for specific tesls or troubleshooting procedures.
64-2
I
a
a

Brake System Indicator Light (cont'd)
- How the Circuit Works
The brake system indicator light comes on to alert
the driver that the parking brake is applied, or that
the brake fluid level is low. lt also comes on as a
bulb test when the engine is cranked.
Parking Brake
With the ignition switch in ON (ll) or START (lll),
voltage is applied through fuse 25 to the brake
system light. When you apply the parking brake, the
switch closes and provides a ground for the light.
The light then comes on to remind you that the
parking brake is applied.
Brake Fluid Level
With the ignition switch in ON (ll) or START (lll),
voltage is applied through fuse 25 to the brake
system light. lf the brake fluid level is low, the brake
fluid level switch closes, providing ground to the
circuit. The brake system light then comes on,
alerting the d verto a low brake fluid level in the
brake master cylinder. (Check brake pad wear
before you add fluid).
Bulb Check
With the ignition switch in START (lll) and clutch
pedal depressed or A'lT gear selector in PARK (P)
or NEUTRAL (N), voltage is applied through fuse 31
to the brake bulb check circuit. The brake bulb
check circuit closes, allowing current to flow through
the brake system light and bulb check circuit to
ground. The brake system light then comes on to
test the bulb.
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
71-2
a
\fa

How the Gircuit Works
All Except GX
Do not smoke while working on the fuel system.
Keep open flame away trom the work area. Drain
fuel only into an approved container.
A thermistor is mounted in the fuel tank unit. When
the thermistor is cool, its resistance is very high.
When the thermistor's temperature increases, its
resistance decreases. Fuel in the fuel tank transters
heat away lrom the thermistor fast enough to keep it
cool so the thermistor's resistance stays high and
lhe low fuel indicator light does not come on. When
the fuel level drops below the thermistor, the
thermistor's temoerature increases. Without the fuel
to cool it, the thermistor's resislance decreases,
allowing current to llow through the low fuel
indicator light and the thermistor to ground, and the
low fuel indicator light comes on.
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
GX
The PCM turns on the low fuel indicator light when
the fuel level is low. The PCM will also blink the
indicator light when a problem is detected by the
fuel tank pressure sensor or the fuel tank
temperature sensor.
Refer to the Service Manual GX Supplement
(Section 11 , Fuel and Emissions) for specific tests
or troubleshooting procedures.
74-1

Gauges (cont'd)
- How the Gircuit Works
When the ignition switch is in ON (ll) or START (lll),
battery voltage is supplied through fuse 25 to the
gauges in the gauge assembly.
Speedometer and Odometer
The odometer and soeedometer drive circuits
receive pulses from the vehicle speed sensor
(VSS). The pulse rate increases as the car
accelerates. The frequency and duration of these
input pulses are measured and displayed by the
speedometer, odometer and tripmeter.
Tachometer
The tachometer drive circuit receives pulses from
the ignition control module (lCM) in the distributor
assembly or the ECM/PCM. The solid-state
lachometer then displays these pulses as engine
speed. For each 200 pulses per minute from the
ignition control modul€ (lCM) or the ECM/PCM, the
tachometer displays 100 RPM.
Engine Coolant Temperature Gauge
The engine coolant temperature gauge has two
intersecting coils wound around a permanent
magnet rotor. Voltage applied to the coils, through
fuse 25, generates a magnetic lield. The magnetic
field, controlled by the coolant temperature sending
unit, causes the rotor to rotate and the gauge
needle to move. As the resistance in the sending
unit varies, current through the gauge coils
changes. The gauge needle moves toward the coil
with the strongest magnetic field.
The 6ngine coolant temperature sending unit's
resistance varies from about 137 ohms at low
engine temperature to between 3H6 ohms at high
temperature (radiator fan running).
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
81-2
(
Fuel Gauge (All except cX)
The fuel gauge has two intersecting coils wound
around a permanent magnet rotor. Voltage applied
to the coils, through tuse 25, generates a magnetic
field. The magnetic field, controlled by the fuel
gauge sending unit, causes the rotor to rotate and
the gauge needle to move. As the resislance in the
sending unit varies, current through the gauge coils
changes. The gauge needle moves toward the coil
with the strongest magnetic field.
The fuel gauge sending unit's resistance varies
from about 2-5 ohms at full, to about 110 ohms at
empty. When you turn the ignition switch off, the
gauge remains at the last reading until you turn the
ignition switch to ON (ll) or START (lll) again,
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
Fuel Gauge (GX)
The fuel gauge has two intersecting coils wound
around a permanent magnet rotor. Voltage applied
to the coils, through fuse 25, generates a magnetic
field. The magnetic field, controlled by the PCM,
causes the rotor to rotate and the gauge needle to
move. The PCM calculates the gas quantity in the
fuel tank by using the fuel pressure value detected
by the tuel tank pressure sensor and the fuel
temperature value detected by the fuel tank
temperalure sensor, and outputs the signal to the
gauge assembly. The gauge needle moves toward
the coil with the strongest magnetic field.
When you turn the ignition switch off , the gauge
remains at the last reading until you turn the ignition
switch to ON (ll) or START (lll) again. When the
PCM detects a malfunction with the fuel pressure or
temperature, or detects a gas leak, the PCM
reduces the fuel meter to 0.
Refer to the Service Manual GX Supplement
(Section 11 , Fuel and Emissions) for specific tests
or troubleshooting procedures.
a
a

A/T Gear Position Indicator (conrd)
- How the Circuit Works
With the ignition switch in ON (ll) or START (lll),
voltage is applied to the A,/T gear position indicator.
The A,/T gear position switch provides a ground for
each position. As an input is grounded, its indicator
light comes on. lf you select R, for example, ground
will be provided to the input of the A,/T gear position
indicato( and the R indicator will come on.
With the headlight switch in PARK or HEAD, voltage
is applied to the RED/BLK wire terminal. This
changes the indicator panel illumination from fixed
to controlled by the dash lights dimmer input
through the RED wire.
When the powertrain (all except '96-'98 CVT) or
transmission ('96198 CVT) control module (PCM or
TCM) detects an abnormality in the automatic
transmission control system, or when you request
diagnostic trouble codes through the service check
connector, the PCM or TCM will make the D4 (D for
CVT) indicator light blink.
Refer to the Service Manual (Section 14,
Automatic Transmission) for specific tests or
troubleshooting procedures.
\ia
89-2

Front WiperMasher (cont'd)
- How the Circuit Works
When the ignition switch is in ON (ll) or START (lll),
battery voltage is applied to lhe combination wiper
switch. and the windshield wiDer motor.
Low Speed
When you turn the wiper switch to LO, the wiper
motor's low speed winding is grounded through the
BLU wire and the LO speed contacts of the wip€r
switch at G401, and the wipers run at low speed.
ParUOfl
When you turn the wiper switch OFF, the integrated
control unit (PARK input) grounds the wiper motor
through the BLUMHT wire. The cam switch on the
motor signals the integrated control unit that the
wipers are in the PARK position; the control unit
then removes ground from the motor, and the
wipers stop in the PARK position.
High Speed
When the wiper switch is in Hl, the high speed
windings of the windshield wiper motor are
grounded through the BLUIrEL wire and the Hl
contacts of the wiper switch at G401, and the
wipers run at high speed.
Intermittent
When the wiper switch is in lNT, battery voltage is
applied through the YEUBLU wire to the integrated
control unit (lntermittent wiper ON input). The
integrated control unit (lnt€rmittenvPark Wiper
Control) grounds the low speed windings of the
wiper motor and the wipers make a single sweep
every few seconds (See Low Speed above). When
the wiper retums to the PARK position, the park
switch applies battery voltage through the
BLUMHT wire to the integrated control unit (PARK
input), and the wipers stop in the PARK position.
Mist
When you pull the wiper switch down to MIST
position, the high speed windings ot the wiper motor
are grounded through the BLU^/EL wire and the
closed contacts ot the mist switch at G401, and the
wipers make one pass across the windshield at high
speed. The ParUOff function then takes over and
the wipers stop in the PARK position.
Washel
When you pull the wiper switch toward you to turn
on the washer switch, battery vollage is applied to
the washer motor. The motor pumps fluid onto the
windshield until you release the lever; on '98r99
models, the integrated control unit (windshield
washer ON input) s€nses power at the WHT/BLK
wire terminal and runs the wipers whenever the
washer motor runs.
Refer lo the Service Manual (Seclion 23, Electrical)
for specific tests or troubleshooting procedures.
91-2

Power Windows (contd)
- How the Circuit Works
CAUTION: You could iniure your arms, hands, or
fingers if you unintentionally switch the driver's
window to "automatic down" while working in
that door with the power on. Disconnect the
window switch conneclot or the battery when
working in the driver's door.
System Description
The operation of the power windows is controlled by
the main switch in the power window master switch.
When the main switch is in OFF, only the driver's door
window can be opened or closed. With the main
switch ON, all windows can be ooened or closed
either by swtches in the master panel, or swttches in
the doors. The driver's window switch also has an
automatic down mode which is tumed on by pushing
the switch down to its second oosition.
The power windows are driven by reversible motors.
Each motor is protect€d by a built-in circuit breaker.
lf the window switch is held on too long (with the
window obstructed, or after the window is fully up or
down), the circuit breaker opens the circuit. The
circuit breaker resets automaticallv as it cools.
Driver's Window
With the ignition switch in ON, voltage is provided to
the coil of the power window relay through fus€ 24.
The contacts of the power window relay close, and
voltage is applied to the driver's switch. When you
push the power window master switch to UP, voltage
is applied to the driver's window motor. (The motor's
ground path is back through the master power
window switch.) The driver's window motor then
drives the window up. When you push the switch to
DOWN, voltage is applied in the opposite direction
and the motor drives the window down.
Automatic Down (Driver's Window)
With the ignition switch in ON or START, voltage is
applied to the coil of the power window relay. The
contacts of the power window relay close and
voltage is applied lo the power window master
switch. When you push the driveas switch to the
AUTO DOWN position, voltage is applied through
the driver's switch to the driver's window motor. The
control unit receives pulses at the pulser input while
the motor is running. When the window is fully
down, the motor stops, and pulses are no longer
generated by the pulser. This is sensed by the
control unit at the pulser input, and voltage is no
longer applied to the driver's window motor.
Passenger Windows
With the ignition switch in ON, voltage is applied to
the coil of the power window relay through fuse 24.
The contacts of the power window relay then close,
applying voltage to the individual window switches
and the power window master switch. With the
master panel main switch ON, the passenger
windows can be ooerated from the individual
window switches or from tho master panel switches.
When you push the front passengsr's window
switch to UP, voltage is applied to the f ront
passenger's window motor. (The motor is grounded
through the contacts in the front passenger's
window switch and the oower window master
switch.) The window moves up as long as you hold
the switch in the UP position. lf you push the switch
to DOWN, voltage is applied in th€ opposite
direction to the front passenger's window motor, and
the window movss down as long as you hold the
switch in the DOWN Dosition. The window switches
in the other doors operate similarly.
When you push the front passenger's switch in the
master panel to UP, voltage is applied through the
front passenger's window switch contacts to the
front passengefs window motor. (The motor is
grounded through the contacts in the front
passenger's window switch and the power window
master switch.) The window moves up as long as
you hold the switch in the UP position. lf you push
the switch to DOWN, voltage is applied in the
opposite direction to lhe front passenger's window
motor, and the window moves down as long as you
hold the switch in the DOWN position. The other
passenger window switches in the master panel
operate similarly.
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
120-4