1999 DODGE NEON Service Repair Manual

REMOVAL AND INSTALLATION
HORN
REMOVAL
Disconnect connector and remove horn attaching
nuts from the bumper support bracket (Fig. 7).
INSTALLATION
For installation, reverse the above procedures.
Insure that the horn projector does not touch bumper
reinforcement or the sound output may be altered.
HORN RELAY
REMOVAL
(1) Remove the Power Distribution Center cover
and locate the horn relay.
(2) Remove the horn relay (Fig. 5).
INSTALLATION
For installation, reverse the above procedures.
HORN SWITCHES
The Horn Switch is part of the Driver Airbag Mod-
ule. Refer to Driver Airbag Module Removal and
Installation procedures in Group 8M.
Fig. 7 Horn Location
8G - 4 HORNSPL

VEHICLE SPEED CONTROL SYSTEM
CONTENTS
page page
GENERAL INFORMATION
INTRODUCTION......................... 1
DESCRIPTION AND OPERATION
POWERTRAIN CONTROL MODULE.......... 3
SERVO CABLE.......................... 3
SPEED CONTROL SERVO.................. 1
SPEED CONTROL SWITCHES.............. 2
STOP LAMP SWITCH..................... 3
VACUUM RESERVOIR.................... 3
VEHICLE SPEED AND DISTANCE............ 3
DIAGNOSIS AND TESTING
CHECKING FOR DIAGNOSTIC CODES........ 4
ELECTRICAL TESTS AT POWERTRAIN
CONTROL MODULE..................... 7
OVERSHOOT/UNDERSHOOT FOLLOWING
SPEED CONTROL SET................... 6ROAD TEST............................ 3
SERVO VACUUM TEST.................... 6
SPEED CONTROL ELECTRICAL TEST........ 4
SPEED CONTROL SWITCH TEST............ 6
STOP LAMP SWITCH TEST................ 6
VACUUM SUPPLY TEST................... 8
VEHICLE SPEED SENSOR................. 8
REMOVAL AND INSTALLATION
POWERTRAIN CONTROL MODULE......... 10
SPEED CONTROL SERVO CABLE............ 9
SPEED CONTROL SERVO.................. 8
SPEED CONTROL SWITCH................. 8
STOP LAMP SWITCH.................... 8
VACUUM RESERVOIR................... 10
VEHICLE SPEED SENSOR................ 10
GENERAL INFORMATION
INTRODUCTION
The speed control system is electronically con-
trolled and vacuum operated. The electronic control
is integrated into the powertrain control module
which is located in the engine compartment. The con-
trols are located on the steering wheel and consist of
five switches. The ON, OFF, and SET buttons are
located on the left side of the airbag module. The
RESUME/ACCEL, CANCEL and COAST buttons are
located on the right side of the airbag module (Fig.
1). For identification and location of the major com-
ponents (Fig. 2) and (Fig. 3).
The system is designed to operate at speeds above
30 mph (50 km/h).
WARNING: THE USE OF SPEED CONTROL IS NOT
RECOMMENDED WHEN DRIVING CONDITIONS DO NOT
PERMIT MAINTAINING A CONSTANT SPEED, SUCH AS
IN HEAVY TRAFFIC OR ON ROADS THAT ARE WIND-
ING, ICY, SNOW COVERED, OR SLIPPERY.
DESCRIPTION AND OPERATION
SPEED CONTROL SERVO
The servo unit consists of a solenoid valve body,
and a vacuum chamber. The PCM controls the sole-noid valve body. The solenoid valve body controls the
application and release of vacuum to the diaphragm
of the vacuum servo. The servo unit cannot be
repaired and is serviced only as a complete assembly.
Fig. 1 Speed Control Switch
PLVEHICLE SPEED CONTROL SYSTEM 8H - 1

SPEED CONTROL SWITCHES
There are two separate switch pods that operate
the speed control system. The steering-wheel-
mounted switches use multiplexed circuits to provide
inputs to the PCM for ON, OFF, RESUME, ACCEL-
ERATE, SET, DECEL and CANCEL modes. Refer to
the owner's manual for more information on speed
control switch functions and setting procedures.When speed control is selected by depressing the
ON switch, the PCM allows a set speed to be stored
in RAM for speed control. To store a set speed,
depress the SET switch while the vehicle is moving
at a speed between 30 and 85 mph. In order for the
speed control to engage, the brakes cannot be
applied, nor can the gear selector be indicating the
transmission is in Park or Neutral.
The speed control can be disengaged manually by:
²Stepping on the brake pedal
²Depressing the OFF switch
²Depressing the CANCEL switch.
NOTE: Depressing the OFF switch or turning off
the ignition switch will erase the set speed stored
in the PCM.
For added safety,the speed control system is pro-
grammed to disengaged for any of the following con-
ditions:
²An indication of Park or Neutral
²An rpm increase without a VSS signal increase
(indicates that the clutch has been disengaged)
²Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
²The VSS signal increases at a rate of 10 mph
per second (indicates that the co-efficient of friction
between the road surface and tires is extremely low)
²The VSS signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
²If the actual speed is not within 20 mph of the
set speed
The previous disengagement conditions are pro-
grammed for added safety.
Once the speed control has been disengaged,
depressing the ACCEL switch when speed is greater
than 25 mph restores the vehicle to the target speed
that was stored in the PCM.
NOTE: Depressing the OFF switch will erase the
set speed stored in the PCM's RAM.
While the speed control is engaged, the driver can
increase the vehicle speed by depressing the ACCEL
switch. The new target speed is stored in the PCM
when the ACCEL is released. The PCM also has a
9tap-up9feature in which vehicle speed increases at a
rate of approximately 2 mph for each momentary
switch activation of the ACCEL switch. The PCM
also provides a means to decelerate without disen-
gaging speed control. To decelerate from an existing
recorded target speed, depress and hold the COAST
switch until the desired speed is reached, then
release the switch.
Fig. 2 MTX Speed Control System
Fig. 3 ATX Speed Control System
8H - 2 VEHICLE SPEED CONTROL SYSTEMPL
DESCRIPTION AND OPERATION (Continued)

The individual switches cannot be repaired. If one
switch fails, the entire switch module must be
replaced.
STOP LAMP SWITCH
Vehicles equipped with the speed control option use
a dual function stop lamp switch. The switch is
mounted on the brake pedal mounting bracket under
the instrument panel. The PCM monitors the state of
the dual function stop lamp switch. Refer to Group 5,
Brakes for more information on stop lamp switch ser-
vice and adjustment procedures.
SERVO CABLE
The speed control servo cable is connected between
the speed control vacuum servo diaphragm and the
throttle body control linkage. This cable causes the
throttle control linkage to open or close the throttle
valve in response to movement of the vacuum servo
diaphragm.
POWERTRAIN CONTROL MODULE
The speed control electronic control circuitry is
integrated into the Powertrain Control Module
(PCM). The PCM is located in the engine compart-
ment. The PCM speed control functions are moni-
tored by the On-Board Diagnostics (OBD). All OBD-
sensed systems are monitored by the PCM. Each
monitored circuit is assigned a Diagnostic Trouble
Code (DTC). The PCM will store a DTC in electronic
memory for any failure it detects. See On-Board
Diagnostic Tests in this group for more information.
The PCM cannot be repaired and must be replaced if
faulty.
USE THE DRB SCAN TOOL TO REPROGRAM
THE NEW PCM WITH THE VEHICLES ORIGI-
NAL IDENTIFICATION NUMBER (VIN) AND
THE ORIGINAL VEHICLES MILEAGE. IF THIS
STEP IS NOT DONE A DIAGNOSTIC TROUBLE
CODE (DTC) MAY BE SET.
VACUUM RESERVOIR
The reservoir contains a one-way check valve to
trap engine vacuum in the reservoir. When engine
vacuum drops, as in climbing a grade while driving,
the reservoir supplies the vacuum needed to main-
tain proper speed control operation. The vacuum res-
ervoir cannot be repaired and must be replaced if
faulty.
VEHICLE SPEED AND DISTANCE
The 4 speed automatic Transmission Control Mod-
ule (TCM) supplies the speed input to the PCM. The
PCM determines acceleration rates. The speed con-
trol software in the PCM uses vehicle speed and
acceleration to control to the set speed.Vehicles with a 3 speed automatic or manual trans-
mission have a vehicle speed sensor (VSS) mounted
to an adapter near the transmission output shaft.
The sensor is driven through the adapter by a speed-
ometer pinion gear. The VSS pulse signal is moni-
tored by the PCM to determine vehicle speed and to
maintain speed control set speed. Refer to the appro-
priate Powertrain Diagnostic Procedures manual for
diagnosis and testing of this component. Refer to
group 14, Fuel System for Removal/Installation
DIAGNOSIS AND TESTING
ROAD TEST
Perform a vehicle road test to verify reports of
speed control system malfunction. The road test
should include attention to the speedometer. Speed-
ometer operation should be smooth and without flut-
ter at all speeds.
Flutter in the speedometer indicates a problem
which might cause surging in the speed control sys-
tem. The cause of any speedometer problems should
be corrected before proceeding. Refer to Group 8E,
Instrument Panel and Gauges for speedometer diag-
nosis.
If a road test verifies a surge following a set and
the speedometer operates properly see ªOvershoot/
Undershoot on speed control setº.
If a road test verifies an inoperative system, and
the speedometer operates properly, check for:
²A Diagnostic Trouble Code (DTC). If a DTC
exists, conduct tests per the Powertrain Diagnostic
Procedures service manual.
²A misadjusted brake (stop) lamp switch. This
could also cause an intermittent problem.
²Loose or corroded electrical connections at the
servo. Corrosion should be removed from electrical
terminals and a light coating of Mopar Multipurpose
Grease, or equivalent, applied.
²Leaking vacuum reservoir.
²Loose or leaking vacuum hoses or connections.
²Defective one-way vacuum check valve.
²Secure attachment at both ends of the speed
control servo cable.
²Smooth operation of throttle linkage and throttle
body air valve.
²Conduct electrical test at PCM.
²Failed speed control servo. Do the servo vacuum
test.
CAUTION: When test probing for voltage or conti-
nuity at electrical connectors, care must be taken
not to damage connector, terminals or seals. If
these components are damaged, intermittent or
complete system failure may occur.
PLVEHICLE SPEED CONTROL SYSTEM 8H - 3
DESCRIPTION AND OPERATION (Continued)

CHECKING FOR DIAGNOSTIC CODES
When trying to verify a speed control system elec-
tronic malfunction: Connect a DRB scan tool if avail-
able to the data link connector. The connector is
located at left side of the steering column, and at
lower edge of the panel.
(1) A speed control malfunction may occur without
a diagnostic code being indicated.
Refer to Group 25, for further information and use-
age of the DRB scan tool and a more complete list of
Diagnostic Trouble Code.
SPEED CONTROL SLOWS DOWN BY ITSELF
Test vehicle speed sensor, refer to group 8E. If sen-
sor fails replace sensor, if it passes perform the fol-
lowing test:
(1) Perform the speed control switch test on the
DECEL switch, if it fails replace switch.
(2) If the switch passes, conduct the vacuum sup-
ply test.
(3) If it passes, conduct the servo vacuum test. If it
fails replace servo.
(4) If continuity, replace the PCM.
SPEED CONTROL ELECTRICAL TEST
Electronic speed control systems may be tested
using two different methods. One involves use of aDRB. If this test method is desired, refer to the Pow-
ertrain Diagnostic Test Procedures for charging and
speed control system manual.
The other test method uses a volt/ohm meter. The
volt/ohm meter method is described in the following
tests.
If any information is needed concerning wiring,
refer to Group 8W, Wiring Diagrams (Fig. 4).
CAUTION: When test probing for voltage or conti-
nuity at electrical connectors, care must be taken
not to damage connector, terminals, or seals. If
these components are damaged, intermittent or
complete system failure may occur.
When electrical connections are removed, corrosion
should be removed from electrical terminals and a
light coating of Mopar Multi-Purpose Grease, or
equivalent, applied. Inspect connectors for damage
terminals.
A poor connection can cause a complete or inter-
mittent malfunction and is also the only connection
in the circuit, that can not be tested. For this reason,
a loose connection may be misdiagnosed as a compo-
nent malfunction.
SPEED CONTROL DIAGNOSTIC TROUBLE CODES
Hex Code DRB Scan Tool Display Description of Diagnostic Trouble Code
23No Vehicle Speed Sensor
SignalNo vehicle distance (speed) sensor signal detected during
road load conditions.
OFSpeed Control Solenoid
CircuitsAn open or shorted condition detected in the Speed Control
vacuum or vent solenoid circuits.
56MUX S/C Switch High Speed Control switch input above the maximum acceptable
voltage.
57MUX S/C Switch Low Speed Control switch input below the minimum acceptable
voltage.
52S/C Power Relay Or 12V
Driver CircuitMalfunction detected with power feed to speed control servo
solnoids.
Check Engine Lamp will illuminate during engine operation if this Diagnostic Trouble Code was recorded.
8H - 4 VEHICLE SPEED CONTROL SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

Fig. 4 Speed Control Circuit
PLVEHICLE SPEED CONTROL SYSTEM 8H - 5
DIAGNOSIS AND TESTING (Continued)

OVERSHOOT/UNDERSHOOT FOLLOWING SPEED
CONTROL SET
If the operator repeatedly presses and releases the
set button with their foot off of the accelerator (a ªlift
foot setº to begin speed control operation), the vehicle
may accelerate and exceed the desired set speed by
up to 5 MPH (8 km/h) and then decelerate to less
than the desired set speed before finally achieving
the desired set speed.
The Speed Control has an adaptive strategy that
compensates for vehicle-to-vehicle variations in speed
control cable lengths. When the speed control is set
with the vehicle operators foot off of the accelerator
pedal, the speed control thinks there is excessive
speed control cable slack and adapts. If the lift foot
sets are continually used, the speed control over-
shoot/undershoot condition will develop.
To ªunlearnº the overshoot/undershoot condition,
the vehicle operator has to press and release the set
button while maintaining the desired set speed with
the accelerator pedal (not decelerating or accelerat-
ing), and then turn the cruise control switch to the
OFF position (or press the CANCEL button if
equipped) after waiting 10 seconds. This procedure
must be performed approximately 10±15 times to
completely unlearn the overshoot/undershoot condi-
tion.
SERVO VACUUM TEST
(1) Turn ignition switch to the ON position with-
out starting engine. Activate speed control ON
switch.
(2) Disconnect the four-way electrical connector
and the vacuum harness at the servo (Fig. 5).
(3) Connect a jumper wire from Pin 3 of the servo
to Pin 3 of the wire connector.
(4) Ground Pins 2 and 4 in the servo. Do not con-
nect pin 1.
(5) Connect a hand held vacuum pump to the vac-
uum nipple and apply 10 - 15 inches of vacuum.
(6) If servo pulls cable, replace servo.
(7) Ground Pin 1 on servo.
(8) Check that the throttle cable pulls in and holds
as long as the vacuum pump is connected. After one
minute, check if cable is still holding. If cable does
not hold replace the servo.
(9) Disconnect jumper from pin 3. Cable should
return to rest position. If not, replace servo.
(10) Connect 4 way electrical connector and vac-
uum harness to servo.
SPEED CONTROL SWITCH TEST
Refer to the appropriate Powertrain Diagnostic
Manual for switch test valves.
STOP LAMP SWITCH TEST
(1) Remove the stop lamp switch refer to Stop
Switch Removal/Installation in this section. Discon-
nect connector from stop lamp switch (Fig. 6). Using
an ohmmeter, switch continuity may be checked as
follows:
(2) With switch plunger released, there should be
continuity between Pin 5 and Pin 6.
(3) With switch plunger depressed, there should be
continuity:
²Between Pin 1 and Pin 2.
²Between Pin 3 and Pin 4.
(4) If the above results are not obtained, the stop
lamp switch is defective or out of adjustment.
Fig. 5 Servo Harness Connector
Fig. 6 Stop Lamp Wiring
8H - 6 VEHICLE SPEED CONTROL SYSTEMPL
DIAGNOSIS AND TESTING (Continued)

(5) Stop lamp switch adjustment is detailed in
Group 5, Brakes.
ELECTRICAL TESTS AT POWERTRAIN CONTROL
MODULE
(1) Unplug the GRAY 40-way connector from the
Powertrain Control Module (PCM), (Fig. 7).
(2) Remove both steering wheel speed control
switches and disconnect the wire connectors.
(a) Using an ohmmeter, check for continuity
between cavity 41 of the PCM connector and cavity
1 of each speed control switch connector (Fig. 8).
(b) If no continuity, repair as necessary.
(c) Using an ohmmeter, check for continuity
between cavity 41 of the PCM connector and
ground.
(d) If continuity, repair as necessary.
(e) If no continuity, perform the Switch Test.
(f) Plug GRAY 40 way connector into PCM.
(g) Plug switch connectors back into switches.
(3) Unplug speed control servo electrical connector.
(4) Place ignition switch in the ON position and
turn on the speed control system, for the following
tests.(a) Using a voltmeter, measure voltage from cav-
ity 3 of servo connector to ground. Voltmeter
should read ignition voltage. If voltage is low, skip
to Step 7.
(b) Turn speed control and ignition switch OFF.
Using an ohmmeter, place positive lead on pin 3
and negative lead on pin 4 on the speed control
servo. Check continuity from pin 3 to pin 4.
(c) If no continuity, replace the speed control
servo. If continuity is greater than 49 ohms, clean
terminals.
(d) Using an ohmmeter, place positive lead on
pin 3 and negative lead on pin 2 on the speed con-
trol servo. Check continuity from pin 3 to pin 2.
(e) If no continuity, replace the speed control
servo. If continuity is greater than 49 ohms, clean
terminals.
(f) Using an ohmmeter, place positive lead on
pin 3 and negative lead on pin 1 on the speed con-
trol servo. Check continuity from pin 3 to pin 1.
(g) If no continuity, replace the speed control
servo. If continuity is greater than 49 ohms, clean
terminals.
(h) Using an ohmmeter at the servo connector,
place positive lead on cavity 4 and negative lead on
ground. Check continuity from cavity 4 to ground.
If no continuity, repair open circuit
(i) Unplug 2 40-way PCM connectors
(j) Using an ohmmeter, check continuity from
cavity 1 of servo connector to cavity 78 on PCM
connector. If no continuity, repair open circuit
(k) Using an ohmmeter, check continuity from
cavity 1 of servo connector to ground. If continuity,
repair as necessary.
(l) If continuity is OK, check continuity from
cavity 2 of servo connector to cavity 80 of PCM
connector. If no continuity, repair open circuit
(m) Using an ohmmeter, check continuity from
cavity 2 of servo connector to ground. If continuity,
repair as necessary.
(n) Using an ohmmeter, check continuity from
cavity 1 of servo connector to cavity 2 of servo con-
nector. If continuity, repair as necessary.
(o) Reconnect the 4 way connector to servo.
(5) Using an ohmmeter, check continuity from cav-
ity 62 of the PCM connector to ground. If continuity
is OK with brake pedal in unpressed position, pro-
ceed to Step 6.
(a) If no continuity, perform the Stop Lamp
switch test. Replace or adjust switch as required.
(b) If switch passes test, check continuity from
cavity 62 of the PCM connector to cavity 1 of the
stop lamp switch connector. Repair open circuit as
required.
Fig. 7 Powertrain Control Module Location
Fig. 8 PCM 40ÐWay Connectors
PLVEHICLE SPEED CONTROL SYSTEM 8H - 7
DIAGNOSIS AND TESTING (Continued)