ECO mode DODGE RAM 1999 Service Manual Online

allows lock cylinder to mesh with switch. With key in lock cylinder,
turn lock cylinder to RUN position so retaining pin can be depressed.
Install lock cylinder in ignition switch (aligning slot) until
retaining pin engages. Turn key to OFF or LOCK position.
2) Pull on lock cylinder to ensure retaining pin is retained
in ignition switch and cylinder will not come out. On vehicles with
automatic transmission, ensure shifter is in Park and dowel pin on
ignition switch is in Park position. Ensure ignition switch is in LOCK
position. On all models, ensure flag on ignition switch is properly
indexed in Park position. The flag operates steering lock.
3) On vehicles with automatic transmission, apply a light
coating of grease to park lock dowel and park lock slider linkage. See
Fig. 6. Slide park lock slider linkage forward completely, then back .
25" (6 mm). Apply a light coating of grease to column lock flag.
4) Carefully install ignition switch on steering column,
ensuring flag is positioned above steering wheel lock lever, dowel
pins on switch align in holes on steering column and park lock dowel
pin slides into park lock slider linkage (automatic transmission
only). See Fig. 7. Tighten mounting screws to 22-30 INCH lbs. (2.5-3.5
N.m).
5) Connect wiring connectors to ignition switch. Install
upper and lower steering column covers. Tighten screws to 17 INCH lbs.
(2 N.m). Install tilt lever (if equipped). Reconnect negative batter\
y
cable. Check for proper operation of ignition switch in all positions.
Check for proper steering wheel lock operation. Check for proper
automatic shift lock operation.
Fig. 6: Positioning Park Lock Slider Linkage
Courtesy of Chrysler Corp.

Relief Pressure Test
1) Close gauge shutoff valve completely 3 times. Record
highest pressure attained each time. All 3 readings must be greater
than specifications and within 50 psi (3.5 kg/cm

) of each other. See
POWER STEERING PUMP PRESSURE TEST SPECIFICATIONS table. If pressures
are not as specified, replace pump. See POWER STEERING PUMP (GASOLINE)\
or VACUUM/POWER STEERING PUMP (DIESEL) under REMOVAL & INSTALLATION.
CAUTION: DO NOT hold steering wheel against stops more than 4 seconds,
or pump damage may result.
2) Open test valve and turn steering wheel to left and right
stops. Record highest pressure attained at each stop. If output
pressures are not equal against each stop, gear is leaking internally
and must be replaced. See STEERING GEAR under REMOVAL & INSTALLATION.
Shut off engine, remove test gauge, and connect pressure hose.
LUBRICATION
CAPACITY
CAPACITY\
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Models Pts. (L)\
Dakota (4WD) ............................................. 2.5 (1.2\
)
Ram Pickup & Ram Van/Wagon ............................... 2.7 (1.3)\
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FLUID TYPE
CAUTION: DO NOT use Automatic Transmission Fluid (ATF).
Use Mopar Power Steering Fluid (4318055).
FLUID LEVEL CHECK
Check fluid level with engine cold and not running. Remove
fluid level dipstick on pump reservoir. Dipstick should indicate FULL
COLD with fluid temperature of 70-80
F (21-27C). If needed, add fluid
through dipstick opening, and recheck. DO NOT overfill.
HYDRAULIC SYSTEM BLEEDING
Fill power steering pump reservoir to specified level. Start
engine and slowly turn steering wheel to left and right, but DO NOT
contact steering stops in either direction. Stop engine. Inspect
reservoir fluid level and add fluid if necessary. Bleeding process may
have to be repeated several times to completely purge all air from
system.
ADJUSTMENTS
POWER STEERING PUMP BELT
Vehicles are equipped with dynamic tensioner. No adjustment
is required.
POWER STEERING PUMP PULLEY


* S YM PTO M C HEC K L IS T *

1 999 D odge P ic ku p R 1500
SYMPTOM CHECK LIST WORKSHEETS
* PLEASE READ THIS FIRST *
NOTE: This article is intended for general information purposes
only. It does not apply specifically to one make or model.
PURPOSE
Why Use the Symptom Check List Worksheets?
One of the most difficult and critical lines of communication
is between the service customer and the technician. The clearer the
technician understands the customer's concerns, the more likely the
problem will be "fixed right the first time".
The Symptom Check List Worksheets in this article are
designed to improve this communication. When used consistently, they
can be helpful in reducing shop comebacks, increasing technician
productivity, and producing satisfied customers. They also provide
other benefits:
* Reduce "No Trouble Found" problems
* Increase customer involvement
* Customer perceive that "they really care and listen"
* Save time during peak write-up periods
* Reduce recontacting customers for additional information
* Improve night drop information
* Insure all the right questions are asked at write-up
Making the Worksheets a Part of Your Normal Routine
The following information contains ideas that may be helpful
in forming habits that promote daily use of the Symptom Check Lists:
* HAVE THE SERVICE ADVISER FILL OUT THE FORM(S) WITH THE
CUSTOMER WHENEVER POSSIBLE.
* Place them in your night drop for the customer to fill out,
along with an instruction sheet to help them understand what
to do.
* Hand out the worksheets to customers while they wait in line
during the peak morning rush and ask them to fill it out. It
will save time for all concerned and improve the quality of
information received from the customer.
* Make sure it is attached to the hard copy when it goes to the
technician.
* Place a copy with the final repair papers and review it with
the customer at delivery.
* Put a new worksheet in the glovebox of all departing
customers.
* Require that you personally see a copy of all worksheets
filled out for shop comebacks.
* Hold a shop meeting to get employee buy-in and their ideas on
how to make it effective in your shop.
There are many other ways to utilize the concept, but as with
every other idea, successful implementation depends on employee
involvement and buy-in.
SYMPTOM CHECK LIST WORKSHEETS

Fuel Transfer Pump Output Pressure
1) Remove 2 existing filter plug fittings at top of fuel
filter housing. Install 2 spring-loaded one-way check valve fittings
at inlet and outlet port. Install Fuel Pressure Test Gauge (6828) to
inlet port fitting. Prevent engine from starting by removing fuel
injection pump relay. Relay is located in Power Distribution Center
(PDC) next to left battery. Relay location is notated on PDC lid.
2) Crank engine while observing fuel pressure test gauge.
Fuel pressure should be 5-7 psi (0.35-0.49 kg/cm

). Reinstall fuel
system relay to PDC. Start engine. Fuel pressure should be minimum of
10 psi (0.7 kg/cm

). Because fuel injection pump relay was removed, a
Diagnostic Trouble Code (DTC) may have been set. Use DRB scan tool to
erase DTC. Go to PRESSURE DROP test.
Pressure Drop
Turn engine off. Remove Fuel Pressure Test Gauge (6828) from
inlet port and attach to outlet port. Start engine and note fuel
pressure. Pressure should not be more than 5 psi (0.35 kg/cm

) less
than inlet port pressure in Fuel Transfer Pump Outlet Pressure test.
See FUEL TRANSFER PUMP OUTPUT PRESSURE test. If fuel pressure is not
to specification, replace fuel filter. Go to FUEL SUPPLY RESTRICTION
test.
NOTE: Following test requires use of DRB scan tool and Periphal
Expansion Port (PEP) module. Ensure transfer pump pressure is\
okay before performing following test.
Fuel Supply Restriction
1) Disconnect fuel supply line quick-connect fitting at left
rear side of engine compartment. After disconnecting fuel line,
plastic clip will remain attached to metal fuel line at engine. Remove
clip from metal line. Snap clip into fuel supply hose. Install Rubber
Adapter Hose (6631) into ends of disconnected fuel supply line.
2) Install transducer from PEP module to brass "T" fitting on
rubber adapter hose. Connect DRB scan tool to transducer. Start engine
and record vacuum reading with engine speed at wide open throttle.
3) If vacuum reading is less than 6 in. Hg, check for
restriction in fuel supply line or fuel tank module. Repair fuel
supply line or module for restrictions as necessary. Also check fuel
pump inlet filter at bottom of module for obstructions. Go to AIR LEAK
IN FUEL SUPPLY LINE test.
NOTE: Following test requires use of a 3-foot section of 1/4" I.D.
clear tubing and 1/8" fitting.
Air Leak In Fuel Supply Line
1) Locate 2 test port plug fittings at top of fuel filter
housing. Clean fitting area. Remove test port fitting at fuel inlet
side of housing toward rear of filter housing. Install 1/8" fitting
with 1/4" O.D. nipple in place of test port. Clamp clear tubing to
fitting nipple. Place other end of hose into clear container.
2) To put fuel transfer pump into a 25 second run mode, turn
ignition switch to CRANK position, then release back to RUN position
without starting engine. Wait for air to purge from empty hose before
checking whether air bubbles are present. If bubbles are present,
check for leaks in supply line to fuel tank. If supply line is not
leaking, remove fuel tank module. Remove filter at bottom of module.
Check for leaks between supply nipple at top of module and filter
opening at bottom of module. Replace module as necessary.
Overflow Valve
1) Clean area around overflow valve and fuel return line at
injection pump. Remove overflow valve from pump and banjo fitting.

NOTE: A leaking fuel injector or high-pressure fuel line may cause
a rough idle, Black smoke, poor engine performance, poor fuel
economy and fuel knock. Following procedure is for
determining if fuel injector is defective.
WARNING: DO NOT allow diesel fuel to contact hot engine when checking
fuel injector, as high exhaust temperatures could cause a
fire. Use care when working around high-pressure fuel lines,
as fuel is under extreme pressure and could penetrate skin,
causing personal injury. Wear safety goggles and protective
clothing when checking fuel injectors.
Fuel Injector
1) Since a leaking high-pressure fuel line may cause the same
symptoms, check for leaking high-pressure fuel line before checking
fuel injector. To check for a leaking high-pressure fuel line, start
engine and allow engine to idle.
2) Inspect high-pressure fuel lines and connections for signs
of fuel leakage by placing cardboard over high-pressure fuel line and
connection. Note if leak is being detected by fuel being sprayed onto
cardboard. If leak exists, repair leak by tightening high-pressure
fuel line nut to 18 ft. lbs. (24 N.m) or replacing high-pressure fuel
line as necessary. If high-pressure fuel line is replaced, bleed air
from fuel system. See FUEL LINE BLEEDING under FUEL SYSTEM in REMOVAL,
OVERHAUL & INSTALLATION article.
3) To check for defective fuel injector, start and idle
engine. Loosen high-pressure fuel line nut at fuel injector and listen
for a decrease in engine speed. Tighten high-pressure fuel line nut to
18 ft. lbs. (24 N.m).
4) If fuel injector is operating properly, engine idle speed
should decrease when high-pressure fuel line nut is loosened. Repeat
procedure on each fuel injector.
5) If engine idle speed does not decrease, fuel injector is
defective and should be removed and tested with a diesel fuel injector
tester. Replace fuel injector if fuel injector opening (pop) pressure
is not about 4500 psi (316 kg/cm

).
EMISSION SYSTEMS & SUB-SYSTEMS
INTAKE MANIFOLD AIR HEATER SYSTEM
Intake Manifold Air Heater Preheat/Postheat Cycle
For testing information on intake manifold air heater system,
see DTC P0380: INTAKE AIR HEATER RELAY NO. 1 CONTROL CIRCUIT and DTC
P0382: INTAKE AIR HEATER RELAY NO. 2 CONTROL CIRCUIT tests in SELF-
DIAGNOSTICS - JEEP, TRUCKS & RWD VANS article.
MISCELLANEOUS CONTROLS
NOTE: Although some controlled devices listed here are not
technically engine performance components, they can affect
driveability if they malfunction.
TRANSMISSION
Park/Neutral Switch (A/T Models)
Park/neutral switch is mounted on transmission case, near
shift lever and contains a 3-pin connector. If problem exists in
park/neutral switch or wiring circuit, a Diagnostic Trouble Code (DTC)\
will be stored in Powertrain Control Module (PCM). See DTC P1899: P/N
SWITCH STUCK IN PARK OR IN GEAR test in SELF-DIAGNOSTICS - JEEP,

converter lock-up. ECM uses various input signals such as transmission
temperature, output shaft speed, central module timer, engine speed,
APPS and brake switch position to determine operation of transmission
torque converter clutch solenoid. Transmission torque converter clutch
solenoid is located on transmission valve body.
FUEL SYSTEM
FUEL DELIVERY
Fuel Injection Pump
A camshaft-driven Bosch VP44 in-line fuel injection pump is
used to supply high pressure fuel to each fuel injector in precise
metered amounts at the correct time. See Fig. 2. The pump is timed to
camshaft gear. Pump output is controlled by integral Fuel Pump Control
Module (FPCM). Because of electronic control, idle speeds and pump
timing are not adjustable. See ON-VEHICLE ADJUSTMENTS - TRUCKS -
DIESEL article. FPCM can operate engine if crankshaft position sensor
signal does not exist. Fuel injection occurs near completion of
compression stroke for each cylinder.
Fuel injection pump contains an overflow valve which allows
excess fuel to return to the fuel tank. Overflow valve is located on
side of fuel injection pump and is used to attach the fuel return line
to the fuel injection pump.
Fuel Transfer Pump
Fuel transfer pump is located on driver's side of cylinder
block, above starter. See Fig. 2. A 12 volt, 12-amp electric vane-type
pump supplies low fuel pressure from fuel tank, through fuel
heater/fuel filter/water separator to fuel injection pump. Fuel
transfer pump contains internal check valves to prevent fuel from
bleeding back into fuel tank during engine shutdown. Pump will self
prime with ignition on for 2 seconds. Pump has 2 modes, 100 percent
duty cycle (10 psi) when engine is running and 25 percent duty cycle
(7 psi) when engine is cranking.
Fuel Filter/Water Separator
Fuel filter/water separator, located on left side of engine,
protects injection pump by removing water and contaminants from fuel.
See Fig. 2 . Assembly also includes fuel heater and Water-In-Fuel (WIF)
sensor.
In-Tank Fuel Filter
A separate in-tank fuel filter is attached to bottom of fuel
tank module. In-tank fuel filter does not require service under normal
conditions.
FUEL CONTROL
Fuel Injector
Fuel injector delivers atomized fuel into the cylinder.
During fuel injection, fuel pressure from fuel injection pump
increases to fuel injector opening pressure or pop pressure of 4500
psi (316 kg/cm

). This is the pressure required to lift fuel injector
needle valve from its seat, allowing fuel to be injected into the
cylinder. Once fuel pressure decreases to less then the opening
pressure, a spring forces needle valve closed and stops fuel injection
into the cylinders. Each fuel injector is connected to injection pump
by a high pressure (as much as 17,405 psi) line.
Fuel Injection Timing
Pump output is controlled by integral Fuel Pump Control


E - T H EO RY/O PER ATIO N - R W D - G ASO LIN E

1999 D odge P ic ku p R 1500
1999 ENGINE PERFORMANCE
CHRY - Theory & Operation - Trucks & RWD Vans - Gasoline
Dakota, Durango, Ram Pickup, Ram Van, Ram Wagon
INTRODUCTION
This article covers the basic description and operation of
engine performance related systems and components. Read this article
before working on unfamiliar systems.
COMPUTERIZED ENGINE CONTROLS
POWERTRAIN CONTROL MODULE (PCM)
The PCM is a digital computer that controls ignition timing,
air/fuel ratio, fuel injector pulse width, ignition coil(s), spark
advance, emission control devices, cooling fan, charging system, idle
speed, cruise control (if equipped), fuel pump and tachometer. For PCM\
location, see PCM LOCATION. PCM uses data from various input sources
to control output devices in order to achieve optimum engine
performance for all operating conditions.
PCM has voltage converters that convert battery voltage to
regulated 5-volt output. The 5-volt output powers battery temperature
sensor, Camshaft Position (CMP) sensor on models equipped with
Distributorless Ignition System (DIS) or distributor on models without\
DIS, Crankshaft Position (CKP) sensor, Engine Coolant Temperature
(ECT) sensor, Intake Air Temperature (IAT) sensor, logic circuits,
Manifold Absolute Pressure (MAP) sensor, Throttle Position (TP) sens\
or
and Vehicle Speed Sensor (VSS) on some models.
PCM LOCATION









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Application Location
Dakota & Durango ................. Right Front Fender, Near Firewall
Ram Pickup, Ram Van & Ram Wagon .... On Firewall, Near Wiper Motor









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NOTE: Components are grouped into 2 categories. The first category,
INPUT DEVICES, includes components that control or produce
voltage signals monitored by the PCM. The second category,
OUTPUT SIGNALS, includes components controlled by the PCM
(this is accomplished by the PCM grounding individual
circuits).
INPUT DEVICES
Vehicles are equipped with different combinations of input
devices. Not all devices are used on all models. To determine
component location and input usage on a specific model, see
appropriate wiring diagram in WIRING DIAGRAMS article. Available input
signals include:
A/C Switch
Switch signals PCM that A/C has been selected. PCM then
activates A/C compressor clutch relay and maintains idle speed at a
preprogrammed RPM. This is done through control of Idle Air Control

operating. When ground is supplied to injector by PCM, armature and
pintle inside injector move a short distance against spring and open a
small orifice. Since fuel is under high pressure, a fine spray is
developed.
Modes Of Operation
As input signals to PCM change, PCM adjusts its response to
output devices. Modes of operation come in 2 types, open loop and
closed loop. In open loop mode, PCM is not using input from HO2S and
is responding to preset programming to determine injector pulse width
and ignition timing. In closed loop mode, PCM adjusts ignition timing
and uses input from HO2S to fine tune injector pulse width.
The following inputs may be used to determine PCM mode:
* A/C Control Positions
* A/C Switch
* Battery Voltage
* Brake Switch
* Camshaft Position (CMP) Sensor
* Crankshaft Position (CKP) Sensor
* Engine Coolant Temperature (ECT) Sensor
* Engine Speed (RPM)
* Heated Oxygen Sensor (HO2S)
* Intake Air Temperature (IAT) Sensor
* Manifold Absolute Pressure (MAP) Sensor
* Park/Neutral (P/N) Switch
* Starter Relay
* Throttle Position (TP) Sensor
* Vehicle Speed Sensor (VSS)
From these inputs, PCM determines which mode vehicle is in
and responds appropriately. Not all inputs are used in all modes or by
all models. Modes of operation are:
* Ignition Switch On (Engine Not Running) - This is an open
loop mode. PCM pre-positions IAC motor based on ECT sensor
input. PCM determines atmospheric pressure from MAP sensor
and determines basic fuel strategy. PCM modifies fuel
strategy according to IAT sensor, ECT sensor and TP sensor
inputs. PCM activates ASD relay, which in turn activates fuel
pump for only 2 seconds unless engine is cranked. PCM also
energizes HO2S heater element for approximately 2 seconds
unless engine is cranked.
* Engine Start-Up - This is an open loop mode. When starter is
engaged, PCM receives input from battery voltage, ignition
switch, CKP sensor, CMP sensor, ECT sensor, IAT sensor, MAP
sensor and TP sensor. Based on these inputs, voltage is
applied to fuel injectors with PCM controlling injection
sequence, rate, and pulse width. PCM provides ground for
injectors to fire in proper order.
PCM determines proper ignition timing according to input
received from CKP sensor. If PCM does not receive CKP sensor signal
within 3 seconds after engine begins cranking, fuel injection system
is shut down and a Diagnostic Trouble Code (FTC) is set in PCM memory.\
* Engine Warm-Up - This is an open loop mode. PCM determines
injector pulse width using input information from battery
voltage, CKP sensor, CMP sensor, ECT sensor, IAT sensor, MAP
sensor and TP sensor. PCM also monitors A/C request and P/N
switch (A/T only) for fuel calculation. PCM controls engine
idle speed through IAC motor. PCM controls ignition timing
based on CKP sensor input.

PCM also operates A/C compressor clutch (if A/C is requested)\
through A/C clutch relay. When engine reaches operating temperature,
vehicle will go into idle mode and PCM will begin monitoring HO2S
input and go into closed loop operation.
* Idle - When engine is at operating temperature, this is a
closed loop mode. In idle mode, PCM now adds HO2S signal to
array of inputs used in ENGINE WARM-UP mode. PCM maintains
correct air/fuel ratio by adjusting injector pulse width and
ignition timing. PCM also controls A/C clutch operation (if
A/C is requested).
* Cruise - When engine is at operating temperature, this is a
closed loop mode. Using information from A/C switch, battery
voltage, CKP sensor, ECT sensor, IAT sensor, MAP sensor and
CMP sensor. PCM also monitors A/C request and P/N switch (A/T
only), TP sensor and VSS signals for fuel calculation. PCM
monitors HO2S and adjusts air/fuel ratio as needed. PCM
controls engine idle speed through IAC motor. PCM controls
spark advance as necessary.
* Acceleration - This is an open loop mode. When PCM
recognizes an abrupt increase in throttle position or
manifold pressure as a demand for increased engine output, it
increases injector pulse width in response to increased fuel
demand. HO2S signals are ignored.
* Deceleration - This is an open loop mode when engine is at
operating temperature and under deceleration. When PCM
receives inputs signaling a closed throttle and an abrupt
decrease in manifold pressure, it reduces injector pulse
width to lean air/fuel mixture. Under certain RPM and closed
throttle position conditions, HO2S signals are ignored and
PCM cuts off fuel injection until idle speed is reached. PCM
also drives IAC motor for smooth transition to idle mode.
* Wide Open Throttle - This is an open loop mode. When PCM
senses wide open throttle, it grounds fuel injectors in
sequence, it ignores HO2S input and it controls pulse width
to supply a pre-determined amount of additional fuel. PCM
also adjusts spark advance and disengages A/C clutch for
approximately 15 seconds.
* Ignition Switch Off - This is an open loop mode. PCM drives
IAC motor into position in anticipation of next start-up. All
outputs are turned off, no inputs are monitored and PCM shuts
down.
Sequential Fuel Injection (SFI)
Individual, electrically pulsed injectors (one per cylinder)
are located in intake manifold runners. These injectors are next to
intake valves in intake manifold. PCM controls injection timing based
on crankshaft position signal input. PCM regulates air/fuel mixture by
length of time injector stays open (pulse width) based on inputs from
HO2S, ECT sensor, MAP and other sensors.
IDLE SPEED
NOTE: DO NOT attempt to correct a high idle speed condition by
turning factory sealed throttle body throttle plate set
screw. This will not change idle speed of warm engine, but
may cause cold start problems due to restricted airflow.
Idle Air Control (IAC) Motor
IAC motor adjusts idle speed to compensate for engine load
and ambient temperature by adjusting amount of air flowing through by-
pass in back of throttle body. PCM uses ECT sensor, VSS, TP sensor and

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