1988 PONTIAC FIERO Service Repair Manual

3 CRUISE CONTROL
.8 PNKIBLK 39
DO NOT
MEASURE RESISTANCE

r--------------------------------------------------------------------------------------------------------------- I I IGNITION
I I I I SERVO I VACUUM I
I POSITION I
I SENSOR I INPUT I
CONNECTED
TO THROTTLE

CRUISE CONTROL
TROUBLESHOOTING HINTS
Try the following checks before doing the Sys-
tem Check
.
1 . Check vacuum hose for leaks. kinks. andlor
restrictions . Also check Cruise Control
Servo linkage
. Refer to Section 9 for vacuum
hose routing and servo linkage adjustments
.
2 . If the system works except for the Tap-Up
and
TapDown functions. replace the Cruise
Control Module
.
Go to System Check for a guide to normal
operation
.
Go to System Diagnosis for diagnostic tests .
SYSTEM CHECK (ROAD TEST)
Use the System Check Table as a guide to
normal operation
.
COMPONENT LOCATION Page-Figure
Brake Switch
.................... Above brake pedal. on brake pedal support ..... 201- 9-A
Check Valve
..................... Behind engine. to right of master brake cylinder . 201-15-A
Clutch Switch
................... Above clutch pedal. on clutch pedal support .... 201-10-B
Cruise Control Module
............ Behind RH side of IIP ...................... 201-11-A
Cruise Control Servo .............. LH front of engine compartment ............. 201-15-A
Fuse Block
...................... Behind LH side of IIP. below light switch ....... 201-10-A
Vacuum Release Valve
............ Above brake pedal. on brake pedal support ..... 201-10-B
Vacuum Tank ................... Lower LH front corner of engine compartment .. 201-15-A
Vehicle Speed Sensor Buffer
....... Behind RH side of IIP. near ECM ............. 201-13-A
C203 (6 cavities) ................. Behind LH side of IIP. at base of steering column 201-11-A
C207 (15 cavities) ................ Behind RH side of IIP. near ECM ............. 201-13-A
C209 (2 cavities) ................. Behind RH side of IIP. left of Cruise Control
................................. Module 201-11-A
C223 (4 cavities) ................. Behind LH side of IIP. at base of steering column 201-11-A
6102 .......................... LN rear corner of engine compartment ......... 201-15-A
6118 (VIN E)
................... Rear of RH cylinder head .................... 201- 5-B
6118 (VIN F) (VIN 8)
............. Rear of RN cylinder head .................... 201- 5-A
6118 (VIN S)
.................... Rear of RN cylinder head .................... 201- 1-C
S143 (VIN E) .................... Engine harness. RH front of dash ............. 201- 2-A
S143 (VIN
F) (VIN 8) ............. Engine harness. RN front of dash ............. 201- 6-A
S143 (VIN S)
.................... Engine harness. center front of dash ........... 201- 1-A
S204
........................... IIP harness. behind instrument cluster ......... 201-10-A
S217
........................... IIP harness. behind center of IIP .............. 201-10-A
S238
........................... Cruise control harness. near Brake Switch ...... 201-11-A
SYSTEM CHECK TABLE
Car should maintain speed
(Continued on facing page)

CRUISE CONTROL 2
I Slide Cruise Control Switch momentaril~ to RIA I Car should accelerate to former set s~eed I
(Continued from facing page)
--
While cruising, accelerate, then remove foot I car should coast back to set speed
from accelerator
Release Cruise Switch
back to ON
Tap brake pedal
I While cruising, tap Cruise Switch to RIA I Car should increase 1 mph for each tap, up to I
Car should hold new faster speed
Car should coast slower (Cruise disengages)
tap
until 25 mph is reached when cruise
Control will not o~erate I
While cruising, tap Set button
1 Slide Cruise Switch to OFF ten
taps, then system must be reset to a new
speed
Car speed should decrease by
1 mph for each
I Cruise Control turns off 1
0 Refer to System Diagnosis when a result is not normal.
SYSTEM DIAGNOSIS
@ Use the isolation Test below to choose the
proper diagnostic tests.
@ Tests follow the Isolation Test.
Note: Do not press both the SET and RIA
Switches at the same time while the
engine is running. If the Quick Checker
displays
a short light, release the
switches immediately. Shorts can
damage the Quick Checker.
lSOLATlON TEST
Connect: QUICK CHECKER (J-34185, SPECMO QC-3 OR EQUIVALENT) or VOLT-OHMMETER
At: CRUISE CONTROL MODULE CONNECTOR (Disconnected)
Conditions:
@ Ignition Switch: RUN
Test with Quick Checker
(J-34185 or equivalent) or Digital Meter
Test Condition
Cruise Switch OFF
(ISOLATION TEST continued on next page)
All Lights Off
With Quick
Checker,
Correct Response
-
20 VDC
20 VDC
For
Different
Response, Do
Test:
B
Without Quick Checker,
Using a Digital Meter
A&J
M&J
Meter
Range
200 ohms
0 volts
0 volts
Connector
Terminals
J & Ground
A
Correct
Response
0 ohms

CRUISE CONTROL
(ISOLATION
Test
2 3
4
5
6
7
If all
TEST continued from previous page)
Condition
Cruise Switch ON
Cruise Switch ON, Set Switch
pressed
Cruise Switch
in RIA
Cruise Switch ON, drive wheels
turned by hand
Run engine for one minute, then
turn it off. With Ignition Switch in
RUN, and holding Cruise Switch
in
RIA, press Set Switch, wait for
Servo to pull
in and release Set
Switch
Quick Checker not connected
the responses were correct, replace Cruise
With Quick
Checker,
Correct Response
ONIOFF Light On
BRK Light On
VENT Light On
VAC Light On
SPS Light On
RA Light Off
SC Light Off
SC Light On
VAC
& SNORT Lights Off
ONIOFF Light On
RA Light On
VENT & SNORT Lights
Off
VSS Light flashes On and
Off
Vacuum holds the servo
all theway in
-
Control Module and check
Without Quick Checker, For
Using
a Digital Meter Different
Meter
Range
20 VDG
20 VDC
200 ohms
200 ohms
200 ohms
20 VDC
20 VDC
20 VDC
200 ohms
20 VDC
20 VDC
200 ohms
20VDC
Connector Terminals
A&J
G&J
C&J
K&J
F&N
M&J
L&J
L&J
K&J
A&J
M&J
C&J
A&D
Response,
Correct Do
Response Test
Battery voltage B
Battery voltage C
30 to 55 ohms D
30 to 55 ohms E
15 to 25 ohms F
0 volts A
0 volts
A
Battery voltage G
30 to 55 ohms N
Battery voltage A
Battery voltage
I
30 to 55 ohms J
Pulses between
approximately battery
voltage and less than
7 K, L
volts
Connect fused jumper from
CtoMandfromKtoL
before operating switches
200ohms 1 F&J
for proper operation.
Vacuum holds the servo
all the way in M
Over range N

CRUISE CONTROL 13 rn E
TEST A: CRUISE SWITCH SHORT
Check for shorts to voltage in the wires to ter-
m als G (BRN), A (GRY), M (GRYIBLK), L
(DK BLU) of the Module (see schematic).
* If the wires are good, replace the Multi-
Function Lever.
TEST B: POWER ClRCUlT OPEN
1. Check the GAGES Fuse.
2. Check that terminal
J (BLK) is grounded.
3. Disconnect connector
C235 and check for
battery voltage at terminal A of the socket
half with Ignition
in RUN.
* If battery voltage is missing, checklrepair
PNWBLK (239) wire.
4. Check continuity between t
and B (GRN) of the pin half of connector C223
with the Cruise Switch ON.
If the Switch is open, replace the Multi-
Function Lever.
5. Check for an open in GRY (397) wire between
al
B of connector C223 and terminal A
of the module connector.
TEST 6: BRK CIRCUIT OPEN
1. Check for an open Brake Switch or Clutch
Switch (see schematic)
2. Check for an open in the
GRY (397) wire,
BRN
(86) wire or GRYIWNT (987) wire.
TEST D: VENT ClRCUlT OPEN
If you measured less than 30 ohms, perform
Test
J. Otherwise, remove the connector from
the Cruise Control Servo. Measure the
resistance between
terminals A and C of the
Servo.
If
it is greater than 55 ohms, replace the
Servo.
* If it is less than 55 ohms, check for an open
DK
BLUIWHT (403) wire between te
C of the Module and
t
Check that terminal C (BLK) of the Servo
connector is grounded (see schematic).
TEST E: VAC ClRCUlT OPEN
If you measured less than 30 ohms, perform
Test
IF. Otherwise, remove the connector from
the Cruise Control Servo. Measure the
resistance between
t als E and C of the
Servo.
If it is more than 55 ohms, replace the Servo.
If it is less than 55 ohms, check for an open in
the LT GRN (402) wire between t
of the Module and terminal E of the Servo.
Check that terminal C (BLK) of the Servo
Connector is grounded (see schematic).
TEST F: SPS CIRCUIT OPEN
If you measured less than 15 ohms, perform
Test N. Otherwise, remove the connector from
the Cruise Control Servo. Measure the
resistance between terminals
B and D of the
Servo.
r If it is more than 25 ohms, replace the Servo.
* If it is less than 25 ohms, check for an open in
the LT
BLUIBLK (399) wire between termi-
nals
H of the Module and
Servo. Check for an open
wire between
t al F of the Module and
terminal B of the Servo.
TEST 6: SC ClRGUlT OPEN
Disconnect C223 and check the switch con-
tinuity between terminals B (GRN) and D
(RED) of the pin half with the Set Switch
pressed.
* If the Switch is open, replace the Multi-
Function Lever.
If the switch is not open, check for an open in
the DK BLU (84) wire between terminal
D of
connector C223 and te al
L of the
Mod-
ule.
TEST H: VAC CIRCUIT SHORT
Remove the connector from the Servo and mea-
sure resistance between terminals
C and E of
the Servo.
r If it is less than 30 ohms, replace the Servo.
If it is 30 ohms or more, check for a short to
ground in the LT GRN wire from terminal K
of the Module to terminal
E of the Servo.
(Continued on next page)

CRUISE CONTROL
(Continued from previous page)
TEST I: RIA CIRCUIT OPEN
Disconnect C223 and check switch continuity
between terminals A (BLU) and C (YEL) of the
pin half of the Cruise Switch in RIA.
0 If the switch is open, replace the Multi-Func-
tion Lever.
If the switch is not open, check for an open in
the
GRYIBLK (87) wire between terminal C
of connector C223 at terminal M of the Mod-
ule.
TEST J: VENT CIRCUIT SHORT
Remove the connector from the Servo and mea-
sure resistance between terminals
A and C of
the Servo.
If it is less than 30 ohms, replace the Servo.
If it is 30 ohms or more, check for a short to
ground in the DK
BLUIWHT wire from ter-
minal C of the Module to terminal A of the
Servo.
TEST K: VSS ClRCUlT OPEN
If the VSS light does not come on, or the volt-
age between terminals A (GRY) and D (BRN)
remains less than 7 volts, check for an open in
the BRN (437) wire or the RED (381) wire from
the Vehicle Speed Sensor Buffer. Refer to page
33-0 for diagnosis of Vehicle Speed Sensor.
TEST L: VSS CIRCUIT SHORT
If the VSS lights does not go off or Battery
voltage remains between ter
and D
(BRN), check for a short to ground on the
BRN (437) wire or the RED (381) wire from the
Vehicle Speed Sensor Buffer. Refer to page 33-0
for diagnosis of Vehicle Speed Sensor.
TEST M: VACUUM SYSTEM
1. Check for a blocked or leaking vacuum
source.
2. If the vacuum source is good, plug the Vac-
uum Release Port and repeat Test
6 of the
Isolation Test.
If the vacuum now holds the throttle open,
replace or repair the Vacuum Release Valve
or the hose to it.
If the test still fails, replace the Cruise Con-
trol Servo.
TEST N: SPS CIRCUIT SHORT
Disconnect the Cruise Control Servo connector
and repeat Test 7 of the Isolation Test.
If the resistance is now over range, replace
the Cruise Control Servo.
If the resistance is still low, find and repair
the short in the TAN wire from terminal F of
the Cruise Control Module to terminal B of
the Cruise Control Servo.
ClRCUlT OPERATION
The Cruise Control System operates a
mechanical linkage to the throttle by means of a
Vacuum Motor. This is a diaphragm moved by
a vacuum applied to one side. A solenoid oper-
ated valve connects the Vacuum Motor to a
Vacuum Tank. Another solenoid valve vents
the vacuum to reduce the suction. The Cruise
Control Module controls the Vacuum Motor
and the throttle by pulsing these solenoid
valves on and off.
One input to the Module is the vehicle speed.
This input comes from the Vehicle Speed Sen-
sor. If the actual speed signal is different from
the speed that was set into and remembered by
the Module, the Module generates pulses to
change the vacuum and return the vehicle to
the set speed. The Vehicle Speed Sensor is
mounted on the Transmission. Other inputs to
the Module are from the Cruise Switch and the
Set Switch. A disengage input to the Module
comes from a switch on the brake pedal. A
sepe-
rate vacuum shut down of the Cruise Control
comes from the Vacuum Release Valve on the
brake pedal.
The two outputs of the Cruise Control Mod-
ule operate the coils of the Vacuum Valve and
the Vent Valve. Both valves are located in the
Cruise Control Servo. These valves move the
throttle be means of the Vacuum Motor. The
Servo Position Sensor
(SPS) coil senses the
position and motion of the Vacuum Motor. It
feeds this information back to the Module to
provide smooth acceleration while the vehicle is
in Cruise Control.