1999 DODGE RAM Ignition

various switch input operations to adjust IAC motor to obtain optimum
idle conditions. Deceleration stall is prevented by increasing airflow
when throttle is closed suddenly.
IGNITION SYSTEM
NOTE: Pickup equipped with 8.0L engine uses Distributorless
Ignition system (DIS). All other models use a Hall Effect
ignition system.
The PCM completely controls ignition system. During
crank/start mode, PCM will set a fixed amount of spark advance for an
efficient engine start. Amount of spark advance or retard is
determined by inputs that PCM receives from ECT sensor, engine vacuum
and engine RPM. During engine operation, PCM can supply an infinite
number of advance curves to ensure proper engine operation.
DISTRIBUTORLESS IGNITION SYSTEM (DIS)
DIS eliminates mechanical ignition components that can wear
out. PCM has complete ignition control and uses a coil pack, CMP
sensor and CKP sensor to control ignition timing. CMP sensor reads
slots in cam timing sprocket. PCM uses this information along with
information from CKP sensor to determine if fuel injectors and
ignition coils are properly sequenced for correct cylinders.
Basic timing is determined by CKP sensor position and is not
adjustable. One complete engine revolution may be required for PCM to
determine crankshaft position during cranking.
Molded ignition coils are used. Each coil fires 2 paired
spark plugs at the same time. One cylinder is on compression stroke
and other cylinder is on exhaust stroke.
HALL EFFECT IGNITION SYSTEM
This system is equipped with a Hall Effect distributor. See
Fig. 1 . Shutter(s) attached to distributor shaft rotate through
distributor Hall Effect switch, also referred to as a CMP sensor,
which contains a distributor pick-up (a Hall Effect device and
magnet). As shutter blade(s) pass through pick-up, magnetic field is
interrupted and voltage is toggled between high and low. PCM uses this
cylinder position data from CMP sensor, along with engine speed (RPM)
and CKP sensor data, to control ignition timing and injector pulse
width to maintain optimum driveability.
EMISSION SYSTEMS
Vehicles are equipped with different combinations of emission
system components. Not all components are used on all models. To
determine component usage on a specific model, see EMISSION
APPLICATIONS - TRUCKS article.
AIR INJECTION SYSTEM
This system adds a controlled amount of air to exhaust gases,
through air relief valve and check valves, to assist oxidation of
hydrocarbons and carbon monoxide in exhaust stream. Air is injected at
catalytic converters.
CRANKCASE VENTILATION (CCV) SYSTEM
CCV system performs same function as a conventional Positive

Crankcase Ventilation (PCV) system, but does not use a vacuum
controlled valve. See POSITIVE CRANKCASE VENTILATION (PCV).
EVAPORATIVE (EVAP) EMISSIONS SYSTEM
This system stores fuel vapors from fuel tank, preventing
vapors from reaching the atmosphere. As fuel evaporates inside fuel
tank, vapors are routed through vent hoses to charcoal canister where
they are stored until engine is started.
Evaporative Canister Purge Control Solenoid (EVAP-CPCS)
Charcoal canister purging is controlled by PCM through an
EVAP-CPCS. During engine warm-up and for a short period after hot
restarts, PCM energizes EVAP-CPCS, interrupting engine vacuum signal
to charcoal canister.
After engine reaches a predetermined operating temperature
and PCM internal timer has expired, PCM will de-energize EVAP-CPCS,
allowing engine vacuum to purge charcoal canister. EVAP-CPCS will also
be de-energized during certain idle conditions so PCM can update fuel
delivery calibration.
POSITIVE CRANKCASE VENTILATION (PCV)
PCV system uses a vacuum operated valve. A closed engine
crankcase breather/filter, with a hose connecting it to air filter
housing, provides source of air for system. Crankcase blow-by gases
are removed from crankcase through PCV valve with manifold vacuum.
These gases are introduced into incoming air/fuel mixture and become
part of the calibrated mixture.
A non-vacuum operated Crankcase Ventilation (CCV) system is
used on some engines, see CRANKCASE VENTILATION (CCV) SYSTEM.
SELF-DIAGNOSTIC SYSTEM
The PCM monitors several different circuits of engine control
system. If a problem is sensed with a monitored circuit, PCM will
store a Diagnostic Trouble Code (FTC) to aid technician in diagnosis
of system. The Malfunction Indicator Light (MIL), or a scan tool can
be used to read DTCs. For additional information, see SELF-DIAGNOSTICS
- JEEP, TRUCKS & RWD VANS article.
MALFUNCTION INDICATOR LIGHT
Malfunction Indicator Light (MIL) comes on and remains on for\
3 seconds as a bulb test each time ignition switch is turned to ON
position. If PCM receives an incorrect signal or receives no signal
from battery voltage input, charging system, ECT sensor, MAP sensor or
TP sensor, MIL will come on. MIL will also come on if certain
emission-related faults exist. This warns driver that PCM is in limp-
in mode and immediate repairs are necessary. See LIMP-IN MODE under
MISCELLANEOUS CONTROLS. MIL can also be used to display Diagnostic
Trouble Codes (DTCs). For additional information, see SELF-DIAGNOSTICS\
- JEEP, TRUCKS & RWD VANS article.
SERIAL COMMUNICATIONS INTERFACE (SCI)
SCI circuit is used by PCM to send data to and receive data
and sensor activation signals from scan tool. Scan tool uses signals
sent on SCI to display fault messages or Diagnostic Trouble Codes
(DTCs), sensor voltages and device states (On/Off). Scan tool uses S\
CI
to send solenoid and switch activation commands to PCM so that devices
and circuits can be tested. SCI is also used to write SRI mileage to

PCM.
MISCELLANEOUS CONTROLS
NOTE: Although not strictly considered part of engine performance
system, some controlled devices can adversely affect
driveability if they malfunction.
A/C CLUTCH RELAY
A/C clutch relay is controlled by PCM. When A/C or Defrost
mode is selected and PCM receives A/C request signal from evaporator
switch, PCM will cycle clutch on and off through A/C clutch relay.
When this relay is energized during engine operation, PCM will
determine correct engine idle speed through IAC motor.
When PCM senses low idle speed or wide open throttle through
TP sensor, PCM will de-energize A/C clutch relay, preventing A/C
operation.
AUTO SHUTDOWN (ASD) RELAY & FUEL PUMP RELAY
ASD relay and electric fuel pump relay are energized when
ignition is on. These relays are controlled through PCM by switching a
common ground circuit on and off. Following components are controlled
by ASD and fuel pump relays:
* Electric Fuel Pump
* Fuel Injectors
* Generator Field Winding
* Ignition Coil(s)
* HO2S Heating Element
When ignition switch is turned to RUN position, PCM energizes
ASD relay and electric fuel pump relay which powers these components.
If PCM does not receive a CMP and CKP sensor signal within one second
of engine cranking (start-up), PCM will turn ground circuit off and
de-energize ASD relay.
GENERATOR
Powertrain Control Module (PCM) regulates charging system
voltage.
LIMP-IN MODE
Limp-in mode is the attempt by PCM to compensate for failure
of certain components by substituting information from other sources
so that vehicle can still be operated. If PCM senses incorrect data or
no data at all from MAP sensor, TP sensor, ECT sensor or battery
voltage, system is placed into limp-in mode and Malfunction Indicator
Light (MIL) on instrument panel comes on.
If faulty sensor comes back on line, PCM will resume closed
loop operation. On some vehicles, MIL will remain on until ignition is
shut off and vehicle is restarted. To prevent damage to catalytic
converter, vehicle should NOT be driven for extended periods in limp-
in mode.
RADIATOR FAN RELAY
Electric cooling fan is used only on Dakota. Using
information supplied by A/C signal (if equipped), ECT sensor, and VSS,\

Dakota & Durango
1) Raise and support vehicle. Ensure shift lever is in Park.
Release shift cable adjuster lock. Shift cable adjuster lock is
located on shift cable, just below brake booster.
2) Disconnect shift cable from transmission shift lever on
transmission. Ensure transmission is still in Park by rotating
transmission shift lever fully toward rear of vehicle to Park detent.
3) Verify parking sprag on transmission is engaged by
attempting to rotate drive shaft. Install shift cable on transmission
shift lever. Lock shift cable in place by pressing shift cable
adjuster lock downward until it snaps into place.
4) To verify proper adjustment, check that engine only starts
with shift lever in Park and Neutral. If engine starts in any other
gears except Park or Neutral, shift cable may be improperly adjusted
or park/neutral position switch may be defective.
Ram Van/Wagon
1) Raise and support vehicle. Ensure shift lever is in Park.
Unsnap shift cable from ball at transmission shift lever on
transmission. See Fig. 6.
2) Check that transmission is still in Park by rotating
transmission shift lever fully toward rear of vehicle to Park detent
position. Release cable adjuster at transmission end of shift cable to
unlock shift cable. See Fig. 6. Snap shift cable back on ball at
transmission shift lever. Press cable lock inward to secure shift
cable.
3) To verify proper adjustment, ensure engine only starts
with shift lever in Park and Neutral. Shift lever should not move from
Park when ignition switch is in LOCK position. Shift lever should move
from Park when ignition switch is in any position except LOCK
position.
Fig. 6: Locating Cable Adjuster (Ram Van/Wagon)
Courtesy of Chrysler Corp.
SHIFT LINKAGE

Ram Pickup
1) Raise and support vehicle. Inspect shift linkage for worn
components. Replace any damaged or worn grommets or shift linkage
components before adjusting.
2) Ensure shift lever is in Park. Loosen lock bolt on
adjusting swivel. See Fig. 7. Ensure shift rod slides freely in
adjusting swivel. If shift rod fails to slide freely in adjusting
swivel, lubricate shift rod as necessary.
3) Rotate transmission shift lever fully toward rear of
vehicle to the Park detent position. Position adjusting swivel so it
is centered in grommet on torque shaft arm. See Fig. 7. Tighten lock
bolt on adjusting swivel. Check that engine only starts with shift
lever in Park and Neutral. If engine starts in any other gears except
Park and Neutral, shift linkage adjustment is incorrect or
park/neutral position switch is defective.
Fig. 7: Identifying Typical Shift Linkage Components
Courtesy of Chrysler Corp.
THROTTLE VALVE CABLE
1) Ensure shift lever is in Park and ignition is off. Remove
air cleaner. Disconnect throttle valve cable from stud on throttle
lever at throttle body.
2) Ensure throttle lever on throttle body is in idle position
and throttle valve lever on transmission is in idle (fully forward)
position.
3) Using small screwdriver, remove retaining clip from
throttle valve cable. Center end of throttle valve cable with stud on
throttle lever at throttle body within .039" (1.00 mm), and install
retaining clip. Install throttle valve cable on throttle lever.
4) To verify proper adjustment, ensure throttle valve lever
on throttle body and throttle lever on transmission move

VEH IC LE C O M MUNIC ATIO N

1999 D odge P ic ku p R 1500
1999 ACCESSORIES & EQUIPMENT
CHRY - Vehicle Communications
Ram Pickup
IDENTIFYING VEHICLE COMMUNICATION PROBLEMS
Connect scan tool to Data Link Connector (DLC) to retrieve
messages. If scan tool message is blank, disconnect scan tool. Ensure
ground circuit has continuity at DLC terminal No. 4. Ensure 12 volts
exists at DLC terminal No. 16. Check power to DLC terminal No. 16 from
Power Distribution Center (PDC) fuse No. 12. Try another scan tool
and/or cable. If scan tool DTC or fault message is present, see
following bus fault messages list and proceed to appropriate DTC or
fault message:
* BUS (+) & BUS (-) OPEN
* BUS (+) OPEN
* BUS (-) OPEN
* BUS (+) & BUS (-) SHORTED TOGETHER
* BUS BIAS LEVEL TOO HIGH
* BUS BIAS LEVEL TOO LOW
* NO BUS BIAS
* NO RESPONSE AIR BAG CONTROL MODULE
* NO RESPONSE CENTRAL TIMER MODULE
* NO RESPONSE INSTRUMENT CLUSTER
* NO RESPONSE POWERTRAIN CONTROL MODULE
* NO RESPONSE COMPASS/MINI-TRIP SYSTEM
* NO RESPONSE RADIO
* NO TERMINATION
* NOT RECEIVING BUS MESSAGES CORRECTLY
* BUS SHORT TO 5 VOLTS
* BUS SHORT TO BATTERY
* BUS SHORT TO GROUND
BUS (+) & BUS (-) OPEN, (BUS (+) OPEN OR BUS (-) OPEN)
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Disconnect scan tool. Ensure ignition is on. Using an
external voltmeter, measure voltage between ground and DLC terminal
No. 3 (Violet/Brown wire). If voltage is not 1.8-2.3 volts, go to step\
3). If voltage is 1.8-2.3 volts, go to next step.
2) Measure voltage between ground and DLC terminal No. 11
(White/Black wire). If voltage is not 1.8-2.3 volts, go to next step.
If voltage is 1.8-2.3 volts, replace scan tool cable or scan tool.
3) Connect jumper wire between ground and DLC connector
terminal No. 11 (White/Black wire). Turn ignition off. Remove
instrument cluster. Using external ohmmeter, measure resistance
between ground and instrument cluster connector C1 terminal No. 9
(White/Black wire). If resistance is less than 5 ohms, go to next
step. If resistance is 5 ohms or more, repair open White/Black wire.
4) Disconnect jumper wire. Connect jumper wire between ground
and DLC connector terminal No. 3 (White/Black wire). Measure

resistance between ground and instrument cluster connector C1 terminal
No. 10 (Violet/Brown wire). If resistance is less than 5 ohms, replace\
instrument cluster. If resistance is 5 ohms or more, repair open
Violet/Brown wire.
BUS (+) & BUS (-) SHORTED TOGETHER
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Turn ignition off. Disconnect Powertrain Control Module
(PCM). PCM is mounted in right side of firewall. Turn ignition on. If
scan tool does not display BUS (+) & BUS (-) SHORTED TOGETHER, repla\
ce
PCM. If scan tool displays BUS (+) & BUS (-) SHORTED TOGETHER, go to\
next step.
2) Turn ignition off. Disconnect anti-lock brake controller
module. Controller is mounted to top of ABS hydraulic unit. Turn
ignition on. If scan tool does not display BUS (+) & BUS (-) SHORTED\
TOGETHER, replace anti-lock brake controller module. If scan tool
displays BUS (+) & BUS (-) SHORTED TOGETHER, go to next step.
3) Turn ignition off. Disconnect instrument cluster. Turn
ignition on. If scan tool does not display BUS (+) & BUS (-) SHORTED\
TOGETHER, replace instrument cluster circuit board. If scan tool
displays BUS (+) & BUS (-) SHORTED TOGETHER, go to next step.
4) Turn ignition off. Disconnect compass mini-trip computer.
Turn ignition on. If scan tool does not display BUS (+) & BUS (-)
SHORTED TOGETHER, replace compass mini-trip computer. If scan tool
displays BUS (+) & BUS (-) SHORTED TOGETHER, go to next step.
5) Turn ignition off. Disconnect radio connector. Turn
ignition on. If scan tool does not display BUS (+) & BUS (-) SHORTED\
TOGETHER, replace radio. If scan tool displays BUS (+) & BUS (-)
SHORTED TOGETHER, go to next step.
6) Turn ignition off and wait 2 minutes. Disconnect Air Bag
Control Module (ACM). ACM is located under center of instrument panel.\
Turn ignition on. If scan tool does not display BUS (+) & BUS (-)
SHORTED TOGETHER, replace ACM. If scan tool displays BUS (+) & BUS (-\
)
SHORTED TOGETHER, go to next step.
7) Turn ignition off. Disconnect Central Timer Module (CTM).\
CTM is located under left side of instrument panel. Turn ignition on.
If scan tool does not display BUS (+) & BUS (-) SHORTED TOGETHER,
replace CTM. If scan tool displays BUS (+) & BUS (-) SHORTED TOGETHE\
R,
go to next step.
8) Disconnect scan tool from DLC. Using external ohmmeter,
measure resistance between terminals No. 3 (Violet/Brown wire) and No.\
11 (White/Black wire) on DLC connector. If resistance is less than 5
ohms, repair short between Violet/Brown wire and White/Dark Green
wire. If resistance is 5 ohms or more, replace scan tool cable or scan
tool as necessary.
BUS BIAS LEVEL TOO LOW (BUS BIAS LEVEL TOO HIGH)
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Disconnect scan tool. Using an external voltmeter, measure

voltage between ground and DLC connector terminal No. 3 (Violet/Brown
wire). If voltage is not 1.8-2.8 volts, go to step 9). If voltage is
1.8-2.8 volts, go to next step.
2) Measure voltage between ground and DLC connector terminal
No. 11 (White/Black wire). If voltage is not 1.8-2.8 volts, go to next\
step. If voltage is 1.8-2.8 volts, replace scan tool cable or scan
tool.
3) Turn ignition off. Disconnect instrument cluster. Ensure
interior lights are off. Using external ohmmeter, measure resistance
between ground and instrument cluster connector C1 terminal No. 10
(Violet/Brown wire). If resistance is less than 1000 ohms, repair
Violet/Brown wire for short to ground. If resistance is 1000 ohms or
more, go to next step.
4) Measure resistance between ground and instrument cluster
connector C1 terminal No. 9 (White/Black wire). If resistance is less
than 1000 ohms, repair White/Black wire for short to ground. If
resistance is 1000 ohms or more, go to next step.
5) Connect jumper wire between ground and DLC connector
terminal No. 3 (White/Black wire). Measure resistance between ground
and instrument cluster connector C1 terminal No. 10 (Violet/Brown
wire). If resistance is less than 5 ohms, go to next step. If
resistance is 5 ohms or more, repair open Violet/Brown wire.
6) Disconnect jumper wire. Connect jumper wire between ground
and DLC connector terminal No. 11 (White/Black wire). Measure
resistance between ground and instrument cluster connector C1 terminal
No. 9 (White/Black wire). If resistance is less than 5 ohms, go to
next step. If resistance is 5 ohms or more, repair open White/Black
wire.
7) Disconnect jumper wire. Measure resistance between ground
and instrument cluster connector C1 terminal No. 4 (Black/Light Green
wire). If resistance is 5 ohms or less, repair open Black/Light Green
wire. If resistance is more than 5 ohms, go to next step.
8) Measure resistance between ground and instrument cluster
connector C1 terminal No. 5 (Black wire). If resistance is 5 ohms or
less, repair open Black wire. If resistance is more than 5 ohms,
replace instrument cluster.
9) Turn ignition off. Disconnect instrument cluster. Ensure
interior lights are off. Measure resistance between ground and
instrument cluster connector C1 terminal No. 4 (Black/Light Green
wire). If resistance is 5 ohms or less, repair open Black/Light Green
wire. If resistance is more than 5 ohms, go to next step.
10) Measure resistance between ground and instrument cluster
connector C1 terminal No. 5 (Black wire). If resistance is 5 ohms or
less, repair open Black wire. If resistance is more than 5 ohms,
replace instrument cluster.
11) Connect jumper wire between ground and DLC connector
terminal No. 11 (White/Black wire). Measure resistance between ground
and instrument cluster connector C1 terminal No. 9 (White/Black wire).\
If resistance is less than 5 ohms, go to next step. If resistance is 5
ohms or more, repair open White/Black wire.
12) Disconnect jumper wire. Measure resistance between ground
and instrument cluster connector C1 terminal No. 9 (White/Black wire).\
If resistance is less than 1000 ohms, repair White/Black wire for
short to ground. If resistance is 1000 ohms or more, go to next step.
13) Connect jumper wire between ground and DLC connector
terminal No. 3 (White/Black wire). Measure resistance between ground
and instrument cluster connector C1 terminal No. 10 (Violet/Brown
wire). If resistance is less than 5 ohms, go to next step. If
resistance is 5 ohms or more, repair open Violet/Brown wire.
14) Using external ohmmeter, measure resistance between
ground and instrument cluster connector C1 terminal No. 10
(Violet/Brown wire). If resistance is less than 1000 ohms, repair
Violet/Brown wire for short to ground. If resistance is 1000 ohms or