1999 DODGE RAM can bus

of part with damaged threads if
available; otherwise, replace
bushing.
Attaching hardware
threads stripped
(threads missing) ...... A ..... Require replacement of part
with stripped threads if
available; otherwise, replace
bushing.
Binding ................. A .. Require repair or replacement.
Deteriorated, affecting
performance ............ A .. Require repair or replacement.
Distorted, affecting
performance ............ A .. Require repair or replacement.
Leaking (fluid-filled
type) .................. A ............ Require replacement.
Missing ................. C ............ Require replacement.
Noisy ................... 2 .......... (1) Further inspection
required.
Rubber separating from
internal metal sleeve on
bonded bushing ......... A ............ Require replacement.
Seized .................. A ............ Require replacement.
Shifted (out of
position) .............. B .. Require repair or replacement.
Split ................... A ............ Require replacement.
Surface cracking (weather-
checked) ............... .. ........ No service suggested or
required.
( 1) - If noise isolated to bushing, suggest repair or
replacement.
CAUTION: Use only approved lubricant on rubber bushings.
Petroleum-based lubricants may damage rubber bushings.









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CENTER LINKS
CENTER LINK INSPECTION








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Condition Code Procedure
Attaching hardware
incorrect .............. A .......... Require replacement of
incorrect part, if available;
otherwise, replace center link.
Attaching hardware
loose .................. A ... Require repair or replacement
of loose part, if available;
otherwise, replace center link.
Attaching hardware
missing ................ C .. Require replacement of missing
part, if available; otherwise,
replace center link.
Attaching hardware
threads damaged ........ A ... Require repair or replacement
of part with damaged threads,
if available; otherwise,
replace center link.
Attaching hardware
threads stripped
(threads missing) ...... A ..... Require replacement of part
with stripped threads, if

of part with damaged threads if
available; otherwise, replace
bushing.
Attaching hardware
threads stripped
(threads missing) ...... A ..... Require replacement of part
with stripped threads if
available; otherwise, replace
bushing.
Binding ................. A .. Require repair or replacement.
Deteriorated, affecting
performance ............ A .. Require repair or replacement.
Distorted, affecting
performance ............ A .. Require repair or replacement.
Leaking (fluid-filled
type) .................. A ............ Require replacement.
Missing ................. C ............ Require replacement.
Noisy ................... 2 .......... (1) Further inspection
required.
Rubber separating from
internal metal sleeve on
bonded bushing ......... A ............ Require replacement.
Seized .................. A ............ Require replacement.
Shifted (out of
position) .............. B .. Require repair or replacement.
Split ................... A ............ Require replacement.
Surface cracking (weather-
checked) ............... .. ........ No service suggested or
required.
( 1) - If noise isolated to bushing, suggest repair or
replacement.
CAUTION: Use only approved lubricant on rubber bushings.
Petroleum-based lubricants may damage rubber bushings.









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\









\









\









\









\









\


CENTER LINKS
CENTER LINK INSPECTION








\









\









\









\









\









\









\


Condition Code Procedure
Attaching hardware
incorrect .............. A .......... Require replacement of
incorrect part, if available;
otherwise, replace center link.
Attaching hardware
loose .................. A ... Require repair or replacement
of loose part, if available;
otherwise, replace center link.
Attaching hardware
missing ................ C .. Require replacement of missing
part, if available; otherwise,
replace center link.
Attaching hardware
threads damaged ........ A ... Require repair or replacement
of part with damaged threads,
if available; otherwise,
replace center link.
Attaching hardware
threads stripped
(threads missing) ...... A ..... Require replacement of part
with stripped threads, if

* Charging System
* Cruise Control System
* Intake Manifold Air Heater
* Tachometer
* Torque Convertor Clutch Engagement (A/T Only)
* Transmission Overdrive Solenoid (A/T Only) Components are
grouped into 2 categories. The first category covers INPUT
DEVICES, which control or produce voltage signals monitored
by the PCM. The second category covers OUTPUT SIGNALS, which
are components controlled by the PCM. See PCM INPUT SIGNALS
and ECM/PCM OUTPUT SIGNALS.
ECM INPUT SIGNALS
Accelerator Pedal Position Sensor (APPS)
APPS sensor is mounted on top left of engine. See Fig. 2.
Sensor provides DC voltage input signal to Engine Control Module (ECM)\
to indicate throttle position. On previous engines, there were
linkages between accelerator pedal, throttle position sensor and
injection pump. On this engine, no linkage exists between accelerator
pedal and injection pump. ECM uses input signals from APPS sensor to
determine proper fuel delivery. ECM also outputs this signal to PCM.
Battery Voltage
Battery voltage input signal provides operating voltage to
Engine Control Module (ECM). This input signal keeps ECM memory alive
and informs ECM what generator output voltage is when engine is
running. ECM memory is used to store Diagnostic Trouble Codes (DTCs),
store APPS sensor voltages from previous key cycles and provide a
speed control adaptive memory.
Camshaft Position Sensor (CMP)
Camshaft Position (CMP) sensor is a hall effect sensor (0-5
volts switched), located below injection pump in rear face of timing
gear cover. Sensor is not used for fuel control. Sensor is used only
for diagnostic purposes.
CCD Bus Circuits
These circuits are connected between Engine Control Module
(ECM) and Powertrain Control Module (PCM) to allow communication
between modules.
Crankshaft Position Sensor (CKP)
Crankshaft Position (CKP) sensor delivers input signal (35
tooth wheel with gap) to Engine Control Module (ECM) to indicate
engine speed and crankshaft position. ECM uses CKP signal along with
other input signals for controlling injector firing sequence and
timing. Sensor is located below fuel transfer pump, on side of engine
block. See Fig. 2.
Data Link Connector (DLC)
Data Link Connector (DLC) provides an input signal to Engine
Control Module (ECM) when using scan tool to retrieve Diagnostic
Trouble Codes (DTCs) from ECM. Input signal may also be used when
performing various tests on the ECM and electronic control system.
Data link connector is a 16-pin connector located at lower edge of
driver's side of instrument panel, just above accelerator pedal.
Engine Coolant Temperature (ECT) Sensor
Engine coolant temperature sensor delivers input signal to
Engine Control Module (ECM) to indicate engine coolant temperature.
ECM uses input signal for controlling fuel control and timing. Engine
coolant temperature sensor is located on front of head, near

brakelines are attached to and is mounted in the engine compartment.
ECM OUTPUT SIGNALS
APPS & CKP Output To PCM
See ACCELERATOR PEDAL POSITION SENSOR (APPS) OUTPUT FROM ECM
under PCM INPUT SIGNALS.
CCD Bus
These circuits are connected between Engine Control Module
(ECM) and Powertrain Control Module (PCM) to allow communication
between modules.
DLC Output
Data Link Connector (DLC) is connected to Engine Control
Module (ECM). Using a scan tool, data can be retrieved (output) from\
ECM.
5-Volt Sensor Supply Output
Engine Control Module (ECM) supplies a 5-volt reference
signal to the following sensors:
* Crankshaft Position (CKP) Sensor
* Camshaft Position (CMP) Sensor
* Intake Air Temperature (IAT) Sensor
* Engine Oil Pressure Sensor
* Manifold Absolute Pressure (MAP) Sensor
Engine Control Module (ECM) also supplies voltage to the
following sensors:
* Accelerator Pedal Position Sensor (APPS)
* Intake Air Temperature (IAT) Sensor
* Engine Oil Pressure Sensor
* Engine Coolant Temperature (ECT) Sensor
* Manifold Absolute Pressure (MAP) Sensor
* Water-In-Fuel (WIF) Sensor
Fuel Injection Pump Relay
The Engine Control Module (ECM) energizes the fuel injection
pump and integral Fuel Pump Control Module (FPCM) through the relay.
When ignition is turned on, ECM supplies 12 volts to fuel injection
pump relay, located in Power Distribution Center.
Fuel Pump Control Module (FPCM)
Fuel Pump Control Module (FPCM) controls fuel pump using
inputs from Engine Control Module (ECM). FPCM is integral to top of
fuel pump. ECM and FPCM are interconnected together for fuel injection
control.
Fuel Transfer Pump
Engine Control Module (ECM) supplies power to fuel transfer
pump. Transfer fuel pump supplies fuel under low pressure (14 psi)
while engine is running to fuel injection pump. Fuel transfer pump
supplies an excess of fuel to cool fuel injection pump. Excess fuel is
returned to fuel tank by fuel injection pump.
Intake Manifold Air Heater Relays
Intake manifold air heater relays provide voltage to intake
manifold air heater for warming of intake. See Fig. 5. Warming of
intake air aids in engine starting and improved driveability during
cold ambient temperatures. Intake manifold air heater relays are
mounted on inner wheelwell, below driver's side battery. See Fig. 6.

WAIT-TO-START Warning Light
WAIT-TO-START warning light is located on instrument panel,
just below the speedometer. WAIT-TO-START warning light will come on
for a short period and then go off as a bulb and wiring circuit test
each time ignition switch is turned to the ON position. If Engine
Control Module (ECM) determines intake manifold air temperature is
less than 59
F (15C) by input signal received from intake manifold
air temperature sensor, ECM delivers output signal to operate WAIT-TO-
START warning light and intake manifold air heater for a preheat
cycle.
WAIT-TO-START warning light will remain on until intake
manifold air heater preheat cycle is complete. WAIT-TO-START warning
light will flash on and off if intake manifold air temperature sensor
signal to ECM is not within a specified value and Diagnostic Trouble
Code (FTC) will be stored in ECM memory.
WATER-IN-FUEL Warning Light
WATER-IN-FUEL warning light is located on instrument panel,
just below tachometer. WATER-IN-FUEL warning light will come on for a
short period and then go off as a bulb and wiring circuit test each
time ignition switch is turned to the ON position. If Engine Control
Module (ECM) determines water exists in fuel/water separator by input
signal from Water-In-Fuel (WIF) sensor, ECM will deliver output signal\
to turn on the WATER-IN-FUEL warning light.
ECM/PCM OUTPUT SIGNALS
A/C Clutch Relay
The Engine Control Module (ECM) controls A/C compressor
operation by controlling ground circuit for A/C clutch relay. ECM de-
energizes A/C clutch relay if engine coolant temperature is more than
257
F (125C). The A/C clutch relay is located in power distribution
center at driver's side front corner of engine compartment, near the
battery.
Automatic Shutdown (ASD) Relay
The Engine Control Module (ECM) controls ASD operation by
controlling ground circuit for ASD relay. ASD provides voltage to
operate generator field control for charging system. ASD relay is
located in power distribution center at driver's side front corner of
engine compartment, near the battery. Automatic Shutdown (ASD) relay
may also be referred to as Auto Shutdown (ASD) relay.
CCD Bus
These circuits are connected between Engine Control Module
(ECM) and Powertrain Control Module (PCM) to allow communication
between modules.
Cruise Control System
Engine Control Module (ECM) regulates cruise control system
operation by controlling vacuum at cruise control servo. Vacuum is
controlled by use of vacuum and vent solenoids in cruise control
servo.
Data Link Connector
Engine Control Module (ECM) provides output information at
Data Link Connector (DLC) when using scan tool to perform various
tests on the ECM and electronic control system. Data link connector is
a 16-pin connector located at lower edge of driver's side of
instrument panel, just above the accelerator pedal.
5-Volt Sensor Supply Output
Powertrain Control Module (PCM) supplies a 5-volt reference

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

more, replace instrument cluster.
NO BUS BIAS
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. Turn ignition 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. 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. 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.
7) Turn ignition on. Using external voltmeter, measure
voltage between ground and instrument cluster connector C1 terminal
No. 2 (Dark Blue/White wire). If voltage is 9.5 volts or less, repair
open Dark Blue/White wire. If voltage is more than 9.5 volts, go to
next step.
8) Turn ignition off. Using external ohmmeter, measure
resistance between ground and instrument cluster connector C1 terminal
No. 4 (Black/Light Green wire). If resistance is 5 ohms or less, go to\
next step. If resistance is more than 5 ohms, repair open Black/Light
Green wire.
9) Measure resistance between ground and instrument cluster
connector C1 terminal No. 5 (Black/Orange wire). If resistance is 5
ohms or less, replace instrument cluster. If resistance is more than 5
ohms, repair open Black/Orange wire.
NO RESPONSE AIR BAG CONTROL MODULE
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) Remove and inspect fuse No. 19 from junction block.