1988 PONTIAC FIERO turn signal

Adjust 2 . Filler panel 3 . Electrical connector
1 . Increase Current - Turn adjusting screw 4 . ~~l~/~~~~~
clockwise 5 . Horn
2 . Decrease Current . Turn adjusting screw
counterclockwise
Install or Connect
3 . Current adjustments should be made 1/4 turn
(90") at a time
Horn Assembly
Remove or Disconnect
1 . Six screws from filler panel behind front fascia on
driver's side 1
. Horn
2 . Bolt/screw
3 . Electrical connector
4
. Filler panel
5 . Six screws
Horn Relay
The horn relay is in the convenience center.
behind the instrument panel to the right of the steering
column
. To remove the relay. pull it straight out .
REPLACEMENT LIGHT BULBS
For exterior light replacement procedures. see the rest of this
section
. For interior light replacement procedures. see Section $A
and Section 8C .
EXTERIOR LIGHTS Trade No . ...................................................................................................................... Back-up Lights 1 156
Center
High-Mounted Stoplight ............................................................................................. 577
Front Barking/Turn Signal Eights ..................................................................................... 2057
Fog Lights
............................................................................................................................... H-3
Headlights ....................................................................................................................... H6054 ................................................................................................................ License Plate Lights 194
.................................................................................... Rear Tail/Stop/Turn Signal Lights 2057
Sidemarker Lights (Front and Rear) ...................................................................................... 194 ..................................................................................................................... Underhood Light 211
BNTERBOR LIGHTS Trade No .
......................................................................................... Air Conditioner/Heater Controls 194 .................................................................................................................. Ashtray & Lighter 194 .............................................................................................................. Cargo Compartment 561
................................................................................................ Cluster & Speedometer (Tach) 194 ..................................................................................................................... Console Ashtray 194 ............................................................................................................. Console Compartment 194
Courtesy Lights
..................................................................................................................... 194 ......................................................................................................................... Dome Light 561
Gear Selector Indicator
............................................................................................................ 74 .......................................................................................... Headlight High-Beam Indicator 194
Indicator Lights
..................................................................................................... Brake System Warning 194
With Gages
........................................................................................................................ 74
............................................................... Charging System Warning (except Rally Gages) 194 .................................................................................................................... Choke Warning
194
With Gages
........................................................................................................................ 74
...................................................................... Oil Pressure Warning (except Rally Gages) 194 ............................................................................................................ Seat Belt
Reminder 194
With Gages
.................................... ... ................................................................................. 74 ............................................................................................. Service Engine Soon Warning 194
With Gages
..................................................................................................................... 74 ............................................................ Temperature Gage Warning (except Rally Gages) 194
........................................................................................................................ Reading
Light 906 ............................................................................................................ Turn Signal Indicators 194

LIGHTING SYSTEMS AND HORNS 8B-11
2-HORN LEADS 3-SIDE MARKER
4-HEADLAMP
%-TURN SIGNAL PARK LAMP
6-HEADLAMP MOTOR RELAY
7-HEADLAMP MOTOR JUMPER
8 -HEADLAMP ISOLATION RELAY
9- BRAKE PRESS. WARNING SW.
10-TO
SIDE MARKER
11-HORNS
12-TO
HEADLAMP
13-ENGINE HARNESSCONNECTOR
14-BULKHEAD CONNECTOR
15-CONNECTOR END CAP
16-HEADLAMP MOTOR ISOLATION RELAY
Fig. 8B-1 1 Forward Light Wiring

842-2 INSTRUMENT PANEL. GAGES & CONSOLE
Pinion Gear
The PINION GEAR is attached to the
traaasmission/transaxle output shaft and rotates in
proportion to the speed of the car. This rotation is
transferred from the pinion gear to the speedometer
head by the speedometer cable.
Photo Speed Sensor
On vehicles that use a mechanical drag-cup
speedometer, the PHOTO SPEED SENSOR is
inserted into the frame of the mechanical speedometer
to provide an electrical feedback to the ECM that
represents vehicle speed. The ECM needs to know how
fast the car is traveling in order to control and operate
the cruise control, cooling fan, and transmission and
evaporative systems.
The photo speed sensor is made up of two special
electronic devices: a Eight-Emitting Diode (LED) and
a photo transistor (a light-sensitive amplifying device).
In the mechanical speedometer, there is a reflective
blade attached to the rotating magnet that is polished
to
reflect light from the LED back to the photo
transistor. Whenever the light strikes the photo
transistor, it conducts electricity. The rate that the
transistor conducts and does not conduct is
proportional to the speed of the magnet, which reflects
the speed of the vehicle. This voltage signal from the
photo transistor is sent to a buffer amplifier (part of the
speed sensor) to be conditioned to a signal the ECM
can understand and use.
PM Generator
The PM (Permanent Magnet) GENERATOR is
a small
AC generator used to sense vehicle speed. The
shaft of the generator fits into a pinion gear in the
transmission/transaxle output shaft (as does the cable
in
a mechanical system).
When the output shaft rotates, the magnet rotates
and generates a voltage. Except for the permanent
magnet, the
PM Generator is exactly like a miniature
alternator. The PM generator is constructed to provide
a voltage whose frequency is about
1.1 cycles per
second for every mile per hour of vehicle speed. This
signal is sent to a buffer amplifier, and then to the
speedometer and the
EGM.
SPEEDOMETER
The speedometer is a road speed indicator with
an odometer to record total mileage, and, on some cars,
a resettable trip odometer.
The major types of speedometers in use are
mechanical instruments and electronic instruments.
Mechanical speedometers use a dial needle to indicate
road speed. Electronic speedometers include
instruments that use a dial indicator and those using
bar-graph
LCD's (Liquid Crystal Displays) or VTF
(Vacuum Tube Fluorescent) displays.
Meehanice! Speedometers
A mechanical speedometer uses a cable driven
(through a pinion gear) by the transmission output
shaft. The cable connects to a magnetic drag-cup inside the
speedometer, which rotates the speedometer
needle. The end of the rotating cable causes a small bar
magnet to rotate within a metal cup. As the magnet
rotates within the cup, it magnetically attracts (drags)
the metal cup along behind it. Two things work to
prevent the cup from rotating as quickly as the magnet.
1. The distance of the magnet from the cup reduces
its effect on the cup.
2. A counterspring is wound around the shaft of the
cup in such a way as to oppose the normal
rotation of the cup. The counterspring loads the
drag-cup to give correct indication of the speed,
prevent needle overshoot, and also to return the
drag cup to a zero point.
Mechanical speedometers require a photo speed
sensor to provide road speed information for the ECM
and other systems, such as Cruise Control and the TCC
(Torque Converter Clutch).
The odometer on these instruments consists of
numbered wheels that are rotated by the speedometer
cable through worm gears.
Quartz Speedometer
The quartz speedometer is an electrically driven
instrument. The indicator needle is driven by a
precision DC motor, and is countersprung to provide
a mechanical load, prevent overshoot of the needle, and
return the indicator to zero when the road speed is
zero.
The source of speed information for a quartz
speedometer is the PM generator. From the PM
generator, speed information goes to the buffer
amplifier to be converted to digital voltage, and then
to the cluster circuitry, which interprets the speed of
the vehicle and produces small voltage to apply to the
speedometer motor.
The odometer on this instrument consists of
numbered wheels that are electrically driven by a
special precision DC motor called a stepper motor.
Digital Speedometer
Digital clusters utilize two types of displays: LCD
(Liquid Crystal Display) and VTF (Vacuum Tube
Fluorescent). They are used in digital speedometers
and bar-graph tachometers, fuel gages, etc.
Speed information entering the cluster from the
buffer amplifier is interpreted by a microcomputer
which controls the speed indication, the tachometer
display and the odometer reading.
The odometers associated with these instruments
utilize either numbered wheels driven by a small motor
or electronic displays. With an electronic display, the
mileage reading is stored in a computer chip (called a
non-volatile RAM chip; NVRAM) that does not
become 'erased' when the vehicle is turned off,
as the
display does not retain the information.
FUEL GAGE
An electrical fuel gage is used on all models,
consisting of an instrument panel gage and a fuel tank
pick-up. The fuel gage indicates the quantity of fuel in

RADIO SYSTEMS AND ANTENNAS 9A-1
SECTION 9A
0 SYSTEMS AND ANTENNAS
CONTENTS
............................................. General Description .................................... 9A-1 Radio Operation 9A-4
Radio
............................................................ 9A-1 ETR AM/FM Stereo (UM-7) ....................... 9A-4
Antennas
........................................................ 9A- 1 ETR Stereo Cassette (UM-6) ......................... 9A-5
Fixed Antenna
.......................................... 9A- 1 ETR Stereo/Cassette/Eaualizer
Diagnosis ........................................................
Radio ....................... .. ................................
Static and Noise .................................... .....
........................................ Popping Noise
Preliminary Diagnostics
.............................
Antenna ................................. .. ................
Tape Player .................. .... .......................
Service Procedures ....................................
Radio and Speakers ........................... .............
Radio Noise Suppression Equipment ............
Stereo Cassette Tape Player ..........................
Tape & Tape Player Care ........................
(UX-1) ..................................................... 9A-6
Advanced ETR
Stereo/Cassette/Equalizer Touch
Control
.................................... ... .............. 9A-7
On-Car Service .............................................. 9A-9
Radio Receiver
............................................ 9A-9
Radio Steering Wheel Controls
..................... 9A-9
Audio Amplifier
........................................... 9A-9
Radio Suppression
..................................... 9A-9
Front Speaker
................................................. 9A-9
............... Rear Speaker; Sub Woofer Speaker
9A-9
Antenna
..................... .. ............................. 9A- 10
GENERAL DESCRIPUION
RADIO ANTENNAS
For radios and radio use see the "Radio Fixed Antenna
Operation" section. ETR means 'Electronically Tuned The
fixed antenna on the right front fender
Receiver'. cannot be adjusted up or down. It may provide
improved reception in rural areas.
- The fixed antenna is designed to withstand most
car washes without damage. If the antenna becomes
slightly bent, you can straighten it by hand. The
antenna can be replaced if severely bent (by vandalism,
etc.). Antennas must be kept clean for good
performance.
RADIO
Because radio problems are normally repaired at
authorized warranty repair stations, the tendency is to
remove the set when a problem is reported, without any
preliminary diagnosis. This results in a large number
of radios being "No Trouble Found" units when
received by the warranty repair stations. Often the
trouble can be corrected without radio removal. wire.
If equipped with
A/C, the blower motor has a
built-in capacitor. Extra electrical equipment added to
the static if not properly grounded or wiring was
improperly routed.
Weak
FM station reception will be affected by
nearby buildings, car speed and direction. These
"flutter" and "fading" conditions are characteristic of
weak FM signals.
ETR radios require clock and button reset if the
battery is disconnected.
Popping Noise
Static and Noise Operating devices such as turn signals, pushing in
cigarette lighter, operating stop lights, etc., may cause
Ground strap connections must be clean and
a popping noise on distant (weak) AM signals.
tight, spark plug cables must be TVRS type and in
good condition and resistance-type spark plugs used.
Preliminary Diagnostics
Capacitors are used in the generator, heating/air
conditioning system, and fuse panel to reduce noise
The inconvenience of driving without a radio
entering the radio through the feed wires. If the car has
while the set is being serviced can often be avoided if
a heater only, the capacitor is in the blower motor feed
the following quick checks are used to eliminate

9A-2 RADlO SYSTEMS - AND ANTENNAS
external radio system problems before removing the
radio for repair:
1. Turn ignition to the accessory position and turn
radio on.
2. On AM-FM radios, if the radio is dead on FM
but the AM plays normally, the radio should be
removed for repair. (The reverse of this condition
does not necessarily call for radio removal).
3. On combination radio/tape units, if the radio
operates properly but the tape player does not,
the unit should be removed for repair. (The
reverse of this condition does not necessarily call
for
radio/tape removal.)
Always determine the exact nature of the radio
problem as an aid to diagnosis. Knowing whether
the condition is intermittent or constant, whether
it occurs with engine
offor running, and whether
it occurs with car parked or moving will help to
pinpoint the problem.
Radio diagnostic information is in Section
8A.
FIXED ANTENNA
Testing For Good Ground of Antenna Mounting
and Connections
Poor grounding of the power antenna, either at
the antenna mounting or at any other connection in the
antenna/lead-in system, can result in seriously reduced
radio performance.
A poor ground can be a reason for
excess ignition noise in
AM reception, or erratic audio.
To check for a poor ground of the antenna,
perform the following:
1. Fully lower antenna.
2. Disconnect antenna motor electrical connector.
3. Remove escutcheon from fender.
4. Attach alligator clip to upper end of antenna to
act as antenna. Leave other end of clip
unattached.
5. Tune radio for weak AM station or signal which
is dependent on clip,
i.e., clip attached, station is
present; clip removed, no station.
6. Remove clip.
7. Ground upper end of antenna to fender
(preferably with knife blade, very short jumper
wire, etc.).
8. If radio station is not received, then the antenna
grounds are good. If the station is still present or
stronger, a poor ground or no ground connection
is present in the system.
Possible ground loss points are:
s Antenna upper mounting (screws loose,
paint overspray, etc.)
e coaxial connector at antenna not tight or
corroded. (Remove to inspect inside the
connector for corrosion.)
e Coaxial connector at radio not tight or
corroded.
e Quick connect connector corroded.
Checking Antennas
Unplug antenna lead-in at back of radio and plug
a test antenna into radio. Make sure test antenna base
is grounded to the car chassis and keep hands off of the
CASSEmE TAPE PLAYER DIAGNOSIS
1. INSPECT I& CLEAN
CAPSTAN
AND HEAD . TRY A KNOWN 600
ADVISE CUSTOMER
TAPE IS WORN QR DEFECTIVE
Fig. 1 Tape Player Diagnosis

9A-6 RADIO SYSTEMS AND ANTENNAS
Press the SEEK button to locate and retain the
next listenable station on the band automatically.
The FM stereo indicator will light when tuned to
an FM station broadcasting in stereo. Stereo
(dual stereo) sound is more realistic.
a Time Set
To set hour, press SET button. The SET indicator
light on the dial will then light up and the radio
frequency will be displayed. Then press SCAN
button, holding SCAN button in until the correct
hour appears.
To set minutes, press SET button. The SET
indicator light will then light up and the radio
frequency will be displayed. Then press SEEK
button, holding SEEK button in until correct
minute appears.
NOTE: After you press the SET button, the radio
frequency will be displayed. The time of day will
be displayed when you press the SCAN or SEEK
button.
a To Operate Tape Player
Insert the cassette squarely into tape door, with
exposed edge entering first. Tape will snap into
position when fully inserted. This automatically
switches the unit from radio to tape operation.
After the cassette has snapped into position,
adjust the volume and fader controls to your
preference.
To advance tape rapidly, press the button next to
the lighted arrow (arrow on button points in the
same direction as lighted arrow). To reverse tape
and located an earlier selection, press the button
which has an arrow pointing in the opposite
direction. To stop fast motion and return to
playing speed, press STOP-EJECT lightly; press
again, but more firmly to eject the tape.
Reversing Sides - Press the upper left
knob (volume control) to play the other
side of the tape. When the end
sf tape is
reached, it automatically reverses and
plays the other side. Tape
indicator Light
When the left indicator light is lit, the top side of
the tape is playing. When the right indicator light
is lit, the bottom side of the tape is playing.
NOTE: When end-of-tape is reached in one
direction, the unit will automatically play the
other side of the tape.
To remove the tape or listen to the radio, push the
STOP-EJECT button.
Press the Dynamic Noise Reduction
(BNRO)
button to reduce high frequency background hiss
on AM, FM, FM stereo, and tape.
For best results, 120 minute tapes are not
recommended.
Figure 803
ETR AM Stereo-FM Stereo Radio Operation
a Povver Button ("PWR") - press to turn radio
on. Press again to turn radio off.
Fig. 803 UX1 Radio
Upper Knob - rotate knob to control volume.
Press knob to recall station frequency when
listening to the radio with the ignition on, or to
display time of day with ignition off. Press knob
to select the other side of the tape when the
cassette is playing.
Loudness Button ("LOUD") - Press to boost
bass frequencies when the system is playing at
low volume.
Balance Control (located behind upper knob)
- turn to adjust left/right speaker balance.
Lower Knob - rotate knob to tune radio stations
manually. Frequency will be displayed during
tuning. Press knob to select AM or FM band
alternately.
Front/Wear Speaker Control (located
behind lower knob)
- rotate control to adjust the
sound between the front and rear speakers.
AM Stereo ("AM-ST") - press to receive AM
stereo.
" Stereo" indicator light will be displayed
when tuned to a station broadcasting
C-QUAM@ AM stereo, provided it is being
received with adequate signal strength in your
locality. When the button is
"out", all AM
stations will be received in monaural,
"single-channel" sound.
C-QuamO is a registered trademark of Motorola,
Inc.
FM Stereo
The stereo indicator light will be displayed
whenever tuned to an FM station broadcasting in
stereo. Stereo (dual channel) sound is more
realistic.
"Stereo" operation means the radio is separating
a stereo broadcast back into the original two
channel, called
"left" and "right."Stereo sound is
noticably realistic to the ear.
5-Band Graphic Equalizer - allows you to
adjust bass, midrange, and treble to suit personal
taste. Move control up to increase frequency
range or down to decrease frequency range.
NOTE: 60 and 250 denote bass; 1K denotes
midrange;
3.5K and 10K denote treble.
Generally, the
Ik control is placed in the center
(detent) position, while the bass and treble
controls are adjusted upwards to varying degrees
Since the
10K control has the most influence on
treble, it may produce high frequency hiss when

CRUISE CONTROL 9B-1
SECTION 9B
SE CONTROL
CONTENTS
General Description ................................... 9B-1
Off/On/Resume/Accel Switch
Operation
................................................ 9B- 1
Set/Coast Button Switch .............................. 9B- 1
Electronic Controller (Module) .................... 9B-2
Servo Unit ..................................................... 9B-2
Speed Sensors ............................................. 9B-3
VSS Buffer Amplifier ................................ 9B-3
PM Generator Speed Signal ..................... 9B-3
Vacuum Supply ............................................. 9B -4
Electrical and Vacuum Release
Switches
..................................................... 9B-4
Electrical Harness ...................................... 9B-4
Diagnosis .................................................. 9B-4
Cruise System Surges .................................... 9B-4
Cruise Set Speed High or Low ..................... 9B-4
Excessive Cruise Speed Loss on Hills .......... 9B-4
Cruise Tap-Up and Tap-Down .................... 9B-4
On-Gar Service (Illustrated) ..................... 9B-6
Cruise Release Switches ............................... 9B-6
............................. Cruise Processor Module 9B-6
Vacuum Harness and Cable Routing -
VIN E ..................................................... 9B-7
Vacuum Harness and Cable Routing -
VIN S ......................................................... 9B-8
Vacuum Harness and Cable Routing -
VIN F,8 ..................................................... 9B-9
Servo Mounting - VIN S,F .......................... 9B-10
....................... Servo and Bracket - VIN E 9B-10
Vacuum Tank - VIN S,F,E ....................... 9B-10
GENERAL DESCRIPTION
Cruise control is a speed control system which
maintains a desired car speed under normal driving
conditions. However, steep grades up or down may
cause variations in the selected speeds. The electronic
cruise control system has the capability to cruise, coast,
resume speed, accelerate, and "tap-up" and
" tap-down" .
The main parts of the cruise control system are
the mode control switches, controller (module), servo
unit, speed sensor, vacuum supply, electrical and
vacuum release switches, and electrical harness.
The cruise control system uses vacuum to operate
a throttle servo unit. The servo unit maintains a desired
car speed by trapping vacuum in the servo unit at the
proper servo position. The controller monitors vehicle
speed and servo position and operates the vacuum and
vent valves in the servo to maintain desired speed. The
controller contains a low speed limit which will prevent
system engagement below a minimum speed of about
25 mph. The operation of the controller is controlled
by mode control switches located in the end of the
directional signal lever. To disengage the system, two
release switches are provided. An electrical release
switch mounted on the brake pedal bracket (brake and
clutch pedal bracket on cars equipped with manual
transmission) disengages the system electrically when
the brake pedal (or clutch pedal) is depressed. A
vacuum release valve, mounted on the brake pedal
bracket, vents the trapped vacuum in the servo to
atmosphere when the brake pedal is depressed,
allowing the servo unit to quickly return the throttle
to idle position.
.
OFF/ON/RESUME/ACCEL SWITCH
(OPERATION)
Figure 1
The Off/On/Resume/Accel Switch has three
positions. This switch turns the cruise control system
ON and OFF and also returns cruise control operation
to the last speed setting when MOMENTARILY
moved towards the R/A position after braking. (Do
not hold the slider in the R/A position
... release it
immediately.) If the slider is held in the R/A position
for more than one second, the system goes into the
Accel mode. To accelerate the car, move the slider
switch to the R/A position and hold it there until the
car reaches the desired speed. When the slider switch
is released, the system will maintain the new cruise
speed. In order to use the Accel mode, the cruise
OFF/ON/Resume/Accel switch must be in the "ON"
position and the car must be above the low speed limit
of
25 mph.
The slide switch can also be used to "tap-up" car
speed. In order to do this the cruise must be engaged
and operating. "Tapping-up" is done by quickly
pressing the slide switch toward the R/A position and
quickly releasing it, or "tapping" the lever. Do not hold
the lever in the R/A position or the system will go into
the Accel mode. "Tap-up" is a function in which cruise
speed can be increased by
1 mph increments (one tap
= 1 mph increase).
SET/COAST BUTTON SWITCH
Figure 1
The cruise control Set/Coast Switch (located in
the end of the turn signal lever) has two positions
-
"Normal" and "Depressed".

98-2 CRUISE CONTROL
Fig. 1 Multi-Function Lever
e The Set Position - With the button switch
depressed and then released (car speed must
exceed the low speed limit point, and the
Off/On/Resume/Accel Switch must be in the
ON position) the cruise speed will be set at the
speed the car was at when the button was
released. Car cruise speed will be within
& 1 mph
of the actual speed at engaged speed. The system
will cruise until either the
Off/On/Resume/Accel Switch is moved to OFF,
the ignition switch is turned off, and/or the
Set/Coast Button is pushed in fully and held.
Pushing the brake pedal (or clutch pedal) releases
the cruise but not the resume capability.
The Coast Position - With the button switch
fully depressed, the driver can raise or lower his
speed. To increase speed, the driver can
accelerate to a new speed, fully depress the switch
and release the button. The controller "forgets"
the previously set speed. An increased control
speed can also be more easily set by the
Off/On/Resume/Accel Switch as previously
described. To decrease cruise speed, the button
switch is held in, disengaging the cruise system,
which allows the throttle to return to the idle
position. When the car has slowed to the aesired
cruise speed, releasing the switch will re-engage
the system.
e The "Tap-Down" Position - In order to do
this the cruise must be engaged and operating.
"Tapping-down" is done by quickly pressing and
releasing the
Set/Coast Button, or "tapping" the
button. Do not hold the button in the depressed
position or the system will go into the "coast"
mode. "Tap-down" is a function in which cruise
speed can be decreased by
1 mph increments (one
tap = 1 mph decrease).
The accelerator may be depressed at any
time
to override the cruise system.
Release of the accelerator will return the
car
te the previous set cruise speed.
NOTICE:
To keep the vehic:e under control, and
to prevent possible vehicle damage, it is not
advisable to use the cruise control on slippery
roads. It is not recommended to use the cruise
control in conditions such as on winding roads or
in traffic of heavy or varying volume. When
traveling down
a steeply graded hill, the cruise control
should be disengaged by depressing the
bralte pedal lightly. The transmission can then be
shifted into a lower gear range to help control
vehicle speed.
ELECTRONIC CONTROLLER (MODULE)
Figure 2
Fig. 2 Controller (Module)
The controller interprets the position of the servo,
the position of the control switches and the output of
the speed sensor. In response to these inputs, the
controller electrically signals the opening or closing of
the vent and vacuum solenoid valves in the servo.
The controller is usually mounted on the pedal
bracket, but is integral with the ECM on some models
with certain engines. For specific location, see the
On-Car Service portion of this section.
SERVO UNIT
Figure 3
The servo consists of a vacuum operated
diaphragm, a normally open solenoid valve to vent the
diaphragm chamber to atmosphere, a normally closed
solenoid valve to connect the diaphragm chamber to
the vacuum source, and a variable inductance position
sensor.
The servo incorporates a steel core which moves
within a coil. Its resulting variable inductance provides
a continuous (voltage) servo position signal to the
controller. This voltage signal is constantly compared
to the vehicle speed signal. This comparison
determines if the cruise system has corrected the speed
error or if additional changes are required.
The servo operates the throttle in response to
signals from the electronic controller as follows:
Steady Cruise State (system engaged and
operating)
- Both vacuum and vent valves are
closed or sealed. The servo has a constant vacuum
on the diaphragm and places no requirements on
the vacuum source, as vacuum is trapped in the
diaphragm chamber.
e Vehicle Losing Speed (due to steep grades or
driver wishes to increase speed by using the Accel
or 'tap-up' feature)
- The controller energizes the
vacuum solenoid to open the vacuum valve to the
vacuum source. This increases the vacuum level