Volvo 850 User manual

CRUISE CONTROL SYSTEM
1995 Volvo 850
1995-96 ACCESSORIES & EQUIPMENT
Volvo Cruise Control Systems
850
NOTE: 1996 850 models are equipped with OBD II diagnostic
connector located in center console. Follow instructions
included with Volvo Scan Tool (998-8686-3) for diagnosis and
testing.
DESCRIPTION & OPERATION
MAIN SWITCH
Cruise control main switch is located at end of turn signal
lever. See Fig. 1. Selector switch has 3 positions, OFF, ON and
RESUME. SET button is at tip of lever.
BRAKE & CLUTCH VALVES
Brake and clutch valves are located on the pedal assembly.
See Fig. 2. Valve adjusts using small plastic catches which hook onto
plunger, holding it in place.
When pedal is up (valve actuated), spring is compressed,
switch is on and vacuum valve is closed. When pedal is down (valve
deactivated), spring pushes plunger back. Electric contact is broken
and vacuum valve opens to allow atmospheric pressure into the system.
Fig. 1: Identifying Cruise Control Main Switch & Connector
Courtesy of Volvo Cars of North America.

Fig. 2: Locating Brake & Clutch Valves & Servo
Courtesy of Volvo Cars of North America.
CONTROL UNIT
Control unit is located in underhood fuse and relay center.
See Fig. 3. Control unit receives signals from sensor and switches.
Main function of control unit is to decide if system can be controlled
based on values and status of input signals, and to regulate system
for optimal function.
Control unit also performs diagnostic functions. This
enables the unit to communicate with the technician via the underhood

diagnostic hookup.
Fig. 3: Locating Control Unit & Terminal Identification
Courtesy of Volvo Cars of North America.
VACUUM PUMP & REGULATOR

Vacuum pump and regulator are contained in one unit, located
in left front corner of engine compartment. When cruise control system
is operating, a 12-volt electric motor pumps vacuum when accelerator
is depressed, sucking air out of tube which leads to vacuum servo. Air
is pumped out through right coupling. Each coupling is equipped with a
check valve to prevent air from entering tube via lower part of pump
housing.
Another tube provides constant atmospheric pressure to upper
pump housing. Regulator releases air to vacuum system when accelerator
is released.
VACUUM SERVO
Vacuum servo is located next to accelerator pedal and
consists of a housing and bellows. See Fig. 2. Bellows is pulled
toward housing when pressure decreases inside bellows, thereby pulling
on wire connecting throttle linkage and bellows.
ADJUSTMENTS
BRAKE & CLUTCH VALVES
Valves are self-adjusting. If manual adjustment is desired,
depress pedal until pedal arm does not make contact with valve. Pull
out plunger as far as possible and pull pedal up slowly. Plastic
catches in valve will hold piston in correct position.
VACUUM SERVO THROTTLE CABLE
Ensure throttle cable is taut at idle. Cable must not affect
position of throttle. See Fig. 2.
SYSTEM TESTS
NOTE: Diagnostic unit for retrieving codes is located in right
front section of engine compartment. Diagnostic unit is
equipped with an LED indicator, activation button and
function select cable. See Fig. 4.
All fault codes contain 3 digits (example 3-1-1). Since codes
have 3 digits, each code requires 3 series of flashes. A 3-second
interval separates series of flashes. Ensure all testing and diagnosis
is performed in the following order.

Fig. 4: Locating Diagnostic Unit
Courtesy of Volvo Cars of North America.
CONNECTING DIAGNOSTIC SYSTEM
Remove covers on diagnostic units. Connect selector cable to
socket No. 2 on diagnostic unit "B". See Fig. 4.
TRANSFER RATE TEST MODE
1) In this test mode, transfer rate (speed of information)

between control unit and diagnostic hookup can be changed. This is
useful if system is read with a display instrument (scan tool). See
TRANSFER RATE TEST CODES table. This step is not necessary if normal
rate is desired, as this rate is loaded with each ignition start.
2) To enter transfer rate test mode, press activation button
4 times, holding button down about one second each time. When LED
lights up, enter selected code. See TRANSFER RATE TEST CODES table.
Enter one digit each time LED lights up. Hold button down about one
second each time it is pressed. If code is entered correctly, LED will
flash code at new rate.
TRANSFER RATE TEST CODES TABLE
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Code Function
3-1-1 ........................................ Normal Rate
3-1-2 .................................... ( 1) Double Rate
3-1-3 .......... 10-Times Normal Rate (Display Instrument)
(1) - Recommended for experienced user of diagnostic
system only.
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CHECKING DIAGNOSTIC WIRE
1) Turn ignition on. Connect a voltmeter between diagnostic
unit "B" socket No. 2 and ground. See Fig. 4. If voltage is about 10
volts, diagnostic wire is okay. Go to COMPONENT TEST MODE. If voltage
is not about 10 volts, go to next step and check ground and voltage to
control unit in addition to wire from socket No. 2 in diagnostic unit
"B" to terminal 4S in control unit. See Fig. 3.
2) Remove cover from underhood relay and fuse unit. Remove
cruise control unit. Connect an ohmmeter between socket No. 2 on
diagnostic unit "B" and control unit terminal 4S. See Fig. 3. Ohmmeter
should show about zero ohms. Connect ohmmeter between ground and
control unit terminal 3S. Ohmmeter should show about zero ohms.
3) Turn ignition on. Connect a voltmeter between ground and
control unit terminal 1S. Battery voltage should be present. If any
measurement is not to specification, check fuse No. 28 and all wiring.
If all measurements are okay, retest using a known-good control unit.
COMPONENT TEST MODE
Introduction
1) This test mode is used to check the components that
comprise cruise control system. By activating components one by one,
and by giving control unit a response code if control unit has
received a signal from component, sensor as well as wiring and
connections can be checked. See COMPONENT TEST MODE CODES table.
2) If correct response code is not obtained, go to
appropriate testing for that particular response code. If correct
response codes are obtained, go to VACUUM SYSTEM CHECK.
COMPONENT TEST MODE CODES TABLE
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Code Activated Component
1-1-3 ................................... Selector ON/OFF
With Selector In ON Position
1-1-3 ............................. Brake Or Clutch Valve
1-2-3 ................................... Selector RESUME
1-3-1 ..................................... Selector SET+
2-1-3 ..................................... Selector SET-

2-2-3 ......................... Shift A/T From "N" To "D"
With Selector In OFF Position
1-3-2 ............................... Depress Brake Pedal
3-1-1 ................................... Several Signals
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Selector Switch Test (Response Code 1-1-3)
1) Response Code 1-1-3 is obtained when selector is switched
from OFF to ON, ON to OFF, or if brake or clutch pedal is depressed
while selector is set to ON. If code cannot be obtained in any
position, voltage is either constantly high (12 volts) or low (zero
volts). If Codes 1-3-1, 1-2-3, or 2-1-3 are also present, there is
voltage to selector switch. Go to BRAKE & CLUTCH PEDAL CHECK (RESPONSE
CODE 1-1-3). If Codes 1-3-1, 1-2-3, or 2-1-3 are not present, go to
next step and check voltage supply to selector switch.
2) Check cruise control fuse No. 28 and replace as necessary.
If fuse is okay, remove upper and lower steering column covers. Check
voltage to cruise control selector switch by turning ignition on.
Connect voltmeter (backprobe) between selector connector terminal No.
2 (Blue/Yellow wire) and ground. See Fig. 1. If battery voltage is not
present, check selector wiring. If battery voltage is present, go to
next step.
3) Connect voltmeter (backprobe) between selector connector
terminal No. 1 (Gray/White wire) and ground. Put switch in ON
position. If battery voltage is not present, replace selector switch.
If battery voltage is present, selector switch is okay.
Brake & Clutch Pedal Check (Response Code 1-1-3)
1) Check voltage to cruise control selector switch. See
SELECTOR SWITCH TEST (RESPONSE CODE 1-1-3). If test verifies cruise
control switch is okay, check voltage at brake and clutch pedal power
circuits. Ensure voltage is entering but not exiting switch. Adjust
switch as necessary. See BRAKE & CLUTCH VALVES under ADJUSTMENTS. If
switches are okay, go to next step.
2) Remove cruise control unit from underhood fuse and relay
center. See Fig. 3. Turn ignition on. Connect voltmeter between ground
and control unit terminal 9T. Battery voltage should be present. If
battery voltage is not present, check voltage circuit to brake and
clutch pedal valves.
Selector SET+ Check (Response Code 1-3-1)
1) Check voltage to cruise control selector switch.
See Fig. 1. See SELECTOR SWITCH TEST (RESPONSE CODE 1-1-3). If test
verifies cruise control switch is okay, connect voltmeter (backprobe)
between cruise control selector switch connector terminal No. 5
(Red/Black wire) and ground. Turn ignition on. Press SET+ button. If
battery voltage is present, go to next step. If battery voltage is not
present, replace selector switch.
2) Remove cruise control unit from underhood fuse and relay
center. See Fig. 3. Connect voltmeter between ground and cruise
control unit base terminal 4T. Turn ignition on. Set cruise control
selector switch to ON position. Press SET+ button. If voltmeter
indicates battery voltage, replace cruise control selector switch. If
voltmeter does not indicate battery voltage, check wiring between
selector switch connector terminal No. 5 (Red/Black wire) and cruise
control unit terminal 4T.
Selector SET- Check (Response Code 2-1-3)
1) Check voltage to cruise control selector switch.
See Fig. 1. See SELECTOR SWITCH TEST (RESPONSE CODE 1-1-3). If test
verifies cruise control switch is okay, connect voltmeter (backprobe)
between cruise control selector switch connector terminal No. 4
(White/Black wire) and ground. Turn ignition on. Press SET- button. If

battery voltage is present, go to next step. If battery voltage is not
present, replace selector switch.
2) Remove cruise control unit from under-hood fuse and relay
center. See Fig. 3. Connect voltmeter between ground and cruise
control unit base terminal 8T. Turn ignition on. Set cruise control
selector switch to ON position. Press SET- button. If voltmeter
indicates battery voltage, replace cruise control selector switch. If
voltmeter does not indicate battery voltage, check wiring between
selector switch connector terminal No. 4 and cruise control unit
terminal 8T.
Selector RESUME Check (Response Code 1-2-3)
1) Check voltage to cruise control selector switch.
See Fig. 1. See SELECTOR SWITCH TEST (RESPONSE CODE 1-1-3). If test
verifies cruise control switch is okay, connect (backprobe) voltmeter
between cruise control selector switch connector terminal No. 3 (Blue
wire) and ground. Turn ignition on. Press RESUME button. If battery
voltage is present, go to next step. If battery voltage is not
present, replace selector switch.
2) Remove cruise control unit from under-hood fuse and relay
center. See Fig. 3. Connect voltmeter between ground and cruise
control unit base terminal 6T. Turn ignition on. Set cruise control
selector switch to ON position. Press RESUME button. If voltmeter
indicates battery voltage, replace cruise control selector switch. If
voltmeter does not indicate battery voltage, check wiring between
selector switch connector terminal No. 3 (Blue wire) and cruise
control unit terminal 6T.
Neutral Start Switch Circuit Disengagement
(Response Code 2-2-3)
1) Turn ignition off. Remove cruise control unit from under-
hood fuse and relay center. See Fig. 3. Connect ohmmeter between
ground and cruise control unit base terminal 3T. With transmission
shift lever in Park or Neutral, ohmmeter should indicate zero ohms
resistance. With transmission shift lever in any other position,
ohmmeter should indicate infinite resistance.
2) If resistances are to specification, replace cruise
control module. If resistances are not to specification, check wiring
between cruise control unit terminal 3T and starter, including neutral
start switch.
Brakelight Switch Check (Response Code 1-3-2)
1) Step on brake pedal. If brakelight illuminates, check
wiring between cruise control unit connector terminal 6S and
brakelight switch. See Fig. 3. If brakelight does not illuminate, go
to next step.
2) Remove driver-side knee protector. Connect voltmeter
between brakelight switch Red wire and ground. If battery voltage is
present, go to next step. If battery voltage is not present, check Red
wire between brake light switch and fuse holder.
3) Connect voltmeter between brakelight switch Yellow wire
and ground. Step on brake pedal. If battery voltage is present, wiring
is okay. If battery voltage is not present, ensure voltage supply is
present at brakelight switch. If voltage supply is present,
replacebrake light switch.
Too Many Simultaneous Input Signals (Response Code 3-1-1)
1) This code is set when control unit receives more than one
input signal within 8 milliseconds. This is usually the result of a
malfunction in a contact or switch, or if wiring has shorted.
2) Activate switches to determine which circuit might have
caused Code 3-1-1 to set. If Code 3-1-1 sets again, check wiring and
switches in relation to which trouble code should have appeared.

VACUUM SYSTEM CHECK
NOTE: To properly test vacuum system, it is necessary to operate
vacuum motor and regulator with jumper wires from control
unit base. Use care when connecting wires as an incorrect
connection can destroy components.
Jumper Wire
Manufacture 2 jumper wires. One should be a single wire with
one normal blade terminal at one end and a thin blade terminal at the
other end. One blade terminal should be thin. Other jumper wire should
be a double wire joined at one end with a normal blade terminal, while
other ends should have thin blade terminals.
Starting Vacuum Pump & Regulator
1) Ensure ignition is off. Remove cruise control unit from
under-hood relay/fuse block. See Fig. 3. Connect single jumper wire
between cruise control unit base terminals 1S and 7T. Connect one end
of other wire to terminal 3S. See Fig. 5. Turn ignition on.
Fig. 5: Connecting Jumper Wires To Control Unit Base Terminals
Courtesy of Volvo Cars of North America.
2) Connect other end of wire connected to terminal 3S to
terminal 9S. Vacuum regulator should click. Connect other wire end to
terminal 7S. Vacuum motor should start while vacuum servo contracts so
control cylinder is pulled up. Remove wire from terminal 7S when
vacuum servo is fully contacted, stopping vacuum motor. If system does
not operate as described, go to step 4). If system operates as
described, go to next step.

3) Let vacuum servo remain contracted for at least 30 seconds
to ensure there is no leakage in vacuum system. See Fig. 2. To release
vacuum servo, remove wire from terminal 9S. Turn ignition off. If
system operates as described, go to step 7). If system does not
operate as described, go to next step.
4) Remove all jumper wires from control unit base. Connect
voltmeter between cruise control unit base terminals 3S and 1S. If
battery voltage is not present, check wiring to cruise control unit.
If battery voltage is present, go to next step.
5) Ensure ignition is off. Connect ohmmeter between control
unit base terminals 7T and 7S. Ohmmeter should indicate about 17 ohms
(internal resistance of vacuum motor). Connect ohmmeter between
control unit base terminals 7T and 9S. Ohmmeter should indicate about
100 ohms (internal resistance of regulator). If resistances are not to
specification, take measurements at individual components (vacuum
motor and regulator) to determine whether fault is in component or
wiring. If all measurements are to specification but vacuum system
still leaks, go to next step.
6) Start vacuum pump and regulator as outlined in steps 1)
and 2). Stop pump so vacuum leaks can be heard. If any valves are
leaking and require adjustment, see BRAKE & CLUTCH VALVES under
ADJUSTMENTS.
7) If system operated as described in step 3), start vacuum
pump and regulator as outlined in steps 1) and 2). Stop vacuum pump
when vacuum servo is fully contracted, but keep regulator connected.
Press brake pedal to release vacuum servo. If vacuum servo does not
release, loosen vacuum hose connection to release servo. Replace
valve.
8) Start vacuum pump again and contract vacuum servo. Press
clutch pedal to release vacuum servo. If servo does not release,
replace valve.
TEST FUNCTION NO. 1
Self Diagnostics
Codes stored in Test Function No. 1 should be read after a
road test because cruise control self diagnostics does not store
codes. Codes are erased when ignition is turned off. Road test must
exceed 22 MPH, otherwise Code 1-2-2 will always be stored, indicating
speed has not reached minimum speed.
NOTE: If engine is turned off after road test, Code 1-2-2 will be
stored. Road test must be repeated.
Beginning Test Function No. 1
Press activation button once for about one second. Read and
note code. Check if more than one code is stored by pressing
activation button once more for about one second. Read and note all
codes until first code is repeated. See SELF DIAGNOSTIC CODES table.
SELF DIAGNOSTIC CODES TABLE
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Code Fault
1-1-1 ........................................... No Fault
1-1-2 .............................. Abnormal Speed Signal
1-2-2 ...................... Speed Below Minimum/No Signal
2-1-1 ............. Voltage Speed/Control Unit Malfunction
2-1-2 ....... Vacuum Pump or Regulator Circuit Malfunction
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Code 1-1-2 & Code 1-2-2
1) Code 1-1-2 is stored if a safety feature has been tripped,

or an abnormal speed signal. Code is stored only if control unit has
had a normal signal at some time during road test and not for
stationary interruptions. Code 1-2-2 is stored when ignition is turned
on. It remains until vehicle speed is greater than 22 MPH for at least
15 seconds. If code remains after a road test at speeds greater than
22 MPH, control unit is not getting a speed signal.
2) If speedometer is not operating correctly, fault is not
with control unit. If speedometer does operate correctly, there is a
proper input signal to instrument cluster. Go to next step and check
if code for 12-pulse output signal is registered with instrument
cluster, fuel and ignition systems.
3) Enter diagnostic test mode No. 1 for instrument cluster by
placing selector cable in socket No. 7 of diagnostic unit "A". Check
for codes. Check for fuel system codes by placing selector cable in
socket No. 2 of diagnostic unit "A". Check for ignition system codes
by placing selector cable in socket No. 6 of diagnostic unit "A".
4) If Code 1-3-1 for instrument cluster, Code 3-1-1 for fuel
system, and Code 3-1-1 for ignition system are set, connection between
instrument cluster and cruise control, fuel system, and ignition
system is shorted to ground or voltage. Remove cruise control unit
from underhood relay/fuse block.
5) Raise and support front of vehicle. Turn ignition on.
Connect voltmeter between cruise control unit base terminal 8S and
ground. Turn front wheels. If voltmeter fluctuates between 0 and 12
volts, replace control module. If voltmeter constantly indicates high
(12 volts) or low (zero volts), check wiring between cruise control
unit and instrument cluster.
Code 2-1-1
Code 2-1-1 is set if malfunction is detected in control unit.
See Fig. 3. Replace control unit and retest system.
Code 2-1-2
Code 2-1-2 is stored if there is short circuit to ground or
voltage in circuit to vacuum pump and regulator. Fault may also be in
control unit. If a Code 2-1-2 fault code is present, test vacuum
system before a road test. See VACUUM SYSTEM CHECK. If trouble code
remains, replace control unit. See Fig. 3.
TEST FUNCTION NO. 2
Codes stored in Test Function No. 2 indicate most recent
reason for cruise control disengagement. This test function can be
used when cruise control disengages without driver input. Code remains
in memory until ignition is turned off, or until cruise control is
disconnected. These codes are not necessarily fault codes, since a
code is also stored after normal disengagement. See DISENGAGEMENT
CODES table.
DISENGAGEMENT CODES TABLE
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Code Disengagement Cause
1-1-4 ............................... Safety Disengagement
1-4-1 ......... Neutral Start Switch Circuit Disengagement
4-1-1 ................ Brake/Clutch Selector Disengagement
1-2-4 ................... Brakelight Circuit Disengagement
2-1-4 ........... Voltage Feed Not Connected/Disengagement
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Beginning Test Function No. 2
Press diagnostic button 5 times, holding activation button
down about one second each time. See Fig. 4. When LED lights up, enter

1-1-1 (one press each time LED lights). Hold activation button down
about one second each time. Read response code.
Code 1-1-4 (Safety Disengagement)
Code 1-1-4 is set in event of a safety disengagement. Safety
disengagement does not necessarily mean something is wrong with
system. Cruise control system disengages automatically during abnormal
conditions such as wheel spin, climbing a steep hill, etc. If this
code is set without a normal safety disengagement, check speed signal
circuit. See CODE 1-1-2 & Code 1-2-2 under TEST FUNCTION NO. 1.
Code 1-4-1 (Neutral Start Switch Circuit Disengagement)
Code 1-4-1 is set if cruise control is disengaged when
transmission shift lever is set in Park or Neutral. If this code is
set without shift lever in one of these positions, control unit
terminal 3T was grounded at moment of disengagement. See NEUTRAL START
SWITCH CIRCUIT DISENGAGEMENT (RESPONSE CODE 2-2-3) under COMPONENT
TEST MODE.
Code 4-1-1 (Brake Selector Disengagement)
Code 4-1-1 is set if cruise control is disengaged by sliding
selector to OFF position or depressing brake or clutch pedal.
Otherwise, control unit terminal 9T did not have battery voltage at
moment of disengagement. This may be caused by play in selector, loose
wires and connectors, or incorrectly adjusted brake or clutch valve.
See BRAKE & CLUTCH PEDAL CHECK (RESPONSE CODE 1-1-3) under COMPONENT
TEST MODE.
Code 1-2-4 (Brakelight Circuit Disengagement)
Code 1-2-4 is set if cruise control is disengaged by
depressing brake pedal and closing brakelight switch. Otherwise,
control unit terminal 6S was not connected to ground through
brakelight bulbs at moment of disengagement. Check for loose wires or
connectors and an incorrectly adjusted brakelight switch. See
BRAKELIGHT SWITCH CHECK (RESPONSE CODE 1-3-2) under COMPONENT TEST
MODE.
Code 2-1-4 (Voltage Feed Not Connected/Disengagement)
1) Code 2-1-4 is set when ignition is turned on and remains
stored until cruise control is engaged using SET one time and
disengaged once. Reason for disengagement is then stored instead of
Code 2-1-4.
2) If Code 2-1-4 is set after disengagement during a test
drive, without engine having been turned off, voltage to control unit
has fallen below minimum level.
REMOVAL & INSTALLATION
BRAKE & CLUTCH VALVE
Removal & Installation
Brake valve is located at brake pedal. Remove clip, vacuum
hoses and connectors from valve. Use care not to damage rubber seals.
To install, reverse removal procedure. Adjust valve. See BRAKE &
CLUTCH VALVES under ADJUSTMENTS.
CRUISE CONTROL SWITCH
Removal & Installation
Turn ignition off. Remove upper and lower steering column
covers. Pull off selector connector and remove 2 screws holding
selector in place. To install, reverse removal procedure.

BRAKELIGHT SWITCH
Removal & Installation
Remove brakelight fuse. Remove brakelight switch connector.
Remove brakelight switch. To install, reverse removal procedure.
WIRING DIAGRAM
Fig. 6: Cruise Control System Wiring Diagram (1995-96)