2003 DODGE RAM ECO mode

(1) Recover refrigerant(Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE).
(2) Remove and disassemble the HVAC housing.
(Refer to 24 - HEATING & AIR CONDITIONING/
DISTRIBUTION/HVAC HOUSING - REMOVAL)
(Refer to 24 - HEATING & AIR CONDITIONING/
DISTRIBUTION/HVAC HOUSING - DISASSEMBLY)
(3) Remove the levers from the driver and passen-
ger side blend air doors (Fig. 2).
(4) Gently slide the drivers or passenger side blend
air door toward the out side of the case and tilt and
lift the doors out of the case.
(5) Inspect doors, seals and case for damage or
binding and repair or replace as required.
INSTALLATION
NOTE: Vehicles equiped with single zone HVAC
systems will only have one blend air door, dual
zone systems have two blend air doors.(1) Place the blend door pivot shafts in to the pivot
holes in the bottom of the lower half of the HVAC
housing.
(2) Blend doors are installed by carefully tipping
the doors in and then sliding each door into position.
(3) Install blend door levers to each door, position
levers so that the doors are able to move smoothly
without any binding. Adjust as required to insure
proper operation.
(4) Check all sealing surfaces and reposition or
replace any seals as required.
(5) Assemble the HVAC housing. (Refer to 24 -
HEATING & AIR CONDITIONING/DISTRIBUTION/
HVAC HOUSING - ASSEMBLY)
(6) Install the HVAC housing in the vehicle. (Refer
to 24 - HEATING & AIR CONDITIONING/DISTRI-
BUTION/HVAC HOUSING - INSTALLATION)
(7) Run calibration test.
BLOWER MOTOR
DESCRIPTION
The blower motor and blower wheel are located in
the passenger side end of the HVAC housing, below
the glove box. The blower motor controls the velocity
of air flowing through the HVAC housing by spinning
a squirrel cage-type blower wheel within the housing
at the selected speed. The blower motor and wheel
can be removed from the housing inside the vehicle
without removing the dash or HVAC housing assem-
bly.
OPERATION
The blower motor will only operate when the igni-
tion switch is in the On position, and the A/C Heater
mode control switch knob is in any position, except
Off. The blower motor receives a fused battery feed
through the blower motor relay whenever the igni-
tion switch is in the On position. The blower motor
battery feed circuit is protected by a fuse in the
Power Distribution Center (PDC). Blower motor
speed is controlled by regulating the ground path
through the A/C Heater control blower motor switch
and the blower motor resistor.
The blower motor and blower motor wheel cannot
be repaired and, if faulty or damaged, they must be
replaced. The blower motor and blower wheel are ser-
viced only as a unit.
Fig. 2 Dual Zone HVAC Housing- (typical single
zone)
1 - Passenger Side Blend Door Lever (if equipped)
2 - Passenger Side Blend Door (if equipped)
3 - Fin Sensor Wire
4 - Lower Blower Motor Mounting Housing
5 - HVAC Evaporator
6 - Fin Sensor
7 - Driver Side Blend Door
8 - Driver Side Blend Door Lever
DRDISTRIBUTION 24 - 25
BLEND DOOR (Continued)

(3) Recover the refrigerant from the refrigerant
system. (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT RECOVERY)
(4) Disconnect the liquid line refrigerant line fit-
ting from the evaporator inlet tube (Fig. 4). (Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING
- STANDARD PROCEDURE - A/C LINE COU-
PLERS)
(5) Disconnect the accumulator inlet tube refriger-
ant line fitting from the evaporator outlet tube.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - STANDARD PROCEDURE - A/C LINE
COUPLERS) Install plugs in, or tape over all of the
opened refrigerant line fittings.
(6) Drain the engine cooling system(Refer to 7 -
COOLING - STANDARD PROCEDURE).(7) Disconnect the heater hoses from the heater
core tubes. Install plugs in, or tape over the opened
heater core tubes.
(8) Unplug all electrical connectors from the actua-
tors and blower motor.
(9) Remove the nuts from the HVAC housing
mounting studs.
(10) Remove the HVAC housing from inside the
vehicle taking care not to allow any remaining cool-
ant to drain on the vehicles interior.
DISASSEMBLY
(1) Remove the HVAC housing from the vehicle
and place it on the workbench. (Refer to 24 - HEAT-
ING & AIR CONDITIONING/DISTRIBUTION/HVAC
HOUSING - REMOVAL)
(2) Unplug the electrical connectors from each
actuator.
(3) Remove the HVAC assembly wiring harness
from the HVAC case.
(4) Remove the blower motor and blower wheel
unit from the HVAC housing. (Refer to 24 - HEAT-
ING & AIR CONDITIONING/DISTRIBUTION/
BLOWER MOTOR - REMOVAL)
(5) Remove the heater core mounting screws and
carefully remove the heater core assembly(Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING/
HEATER CORE - REMOVAL).
(6) Carefully remove the foam seals from the
heater core and evaporator coil tube mounting flange
of the HVAC housing. If the either seal is deformed
or damaged it must be replaced.
(7) Use a screwdriver to pry off the four snap clips
that help secure the upper and lower HVAC housing
halves together.
(8) Remove the screws that secure the upper and
lower HVAC housing halves together.
(9) Carefully separate the upper HVAC housing
from the lower half.
ASSEMBLY
(1) Assemble the upper HVAC housing half to the
lower half. During assembly, be certain of the follow-
ing.
(a) That each of the mode door pivot shaft ends
and the temperature blend door shafts are properly
engaged in there pivot holes.
(b) That the blower motor is properly indexed
and installed.
(c) If the unit is equipped with air conditioning,
that the evaporator coil tube rubber seal is prop-
erly positioned in the grooves in both the upper
and lower HVAC housing halves.
(d) That the evaporator drain opening is clean.
(e) That the evaporator drain shield is installed
correctly.
Fig. 4 HVAC Housing - Dual Zone Shown (Typical -
Single Zone)
1 - Mounting Nut
2 - Passenger Blend Door Actuator (dual zone)
3 - Mounting Nut
4 - Air Intake Spacer
5 - Recirculation Door Actuator
6 - Recirculation Door Assembly
7 - Driver Side Blend Door Actuator
8 - HVAC Housing
9 - Mounting Screw
10 - Defroster Door Actuator
11 - Panel Actuator
24 - 28 DISTRIBUTIONDR
HVAC HOUSING (Continued)

erant system. Refer to the operating instructions sup-
plied by the equipment manufacturer for the proper
care and use of this equipment.
STANDARD PROCEDURE - REFRIGERANT
SYSTEM EVACUATE
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
If the refrigerant system has been open to the
atmosphere, it must be evacuated before the system
can be charged. If moisture and air enters the system
and becomes mixed with the refrigerant, the com-
pressor head pressure will rise above acceptable
operating levels. This will reduce the performance of
the air conditioner and damage the compressor.
Evacuating the refrigerant system will remove the
air and boil the moisture out of the system at near
room temperature. To evacuate the refrigerant sys-
tem, use the following procedure:
(1) Connect a R-134a refrigerant recovery/recy-
cling/charging station that meets SAE Standard
J2210 and a manifold gauge set to the refrigerant
system of the vehicle.
(2) Recover the refrigerant(Refer to 24 - HEATING
& AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE).
(3) Open the low and high side valves and start
the charging station vacuum pump. When the suc-
tion gauge reads 88 kPa (26 in. Hg.) vacuum or
greater, close all of the valves and turn off the vac-
uum pump.
(a) If the refrigerant system fails to reach the
specified vacuum, the system has a leak that must
be corrected. (Refer to 24 - HEATING & AIR CON-
DITIONING/PLUMBING - DIAGNOSIS AND
TESTING - REFRIGERANT SYSTEM LEAKS)
(b) If the refrigerant system maintains the spec-
ified vacuum for five minutes, restart the vacuum
pump, open the suction and discharge valves and
evacuate the system for an additional ten minutes.
(4) Close all of the valves, and turn off the charg-
ing station vacuum pump.
(5) The refrigerant system is now ready to be
charged with R-134a refrigerant. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
STANDARD PROCEDURE - REFRIGERANT
SYSTEM CHARGE
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
After the refrigerant system has been tested for
leaks and evacuated, a refrigerant charge can be
injected into the system. (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - SPECIFICA-
TIONS - CHARGE CAPACITY)
A R-134a refrigerant recovery/recycling/charging
station that meets SAE Standard J2210 must be
used to charge the refrigerant system with R-134a
refrigerant. Refer to the operating instructions sup-
plied by the equipment manufacturer for proper care
and use of this equipment.
The R-134a refrigerant charge capacity for this
vehicle is 0.7371 Kg (26 oz.).
NOTE: Always refer to the HVAC underhood sticker
for current refrigerant charge level and refrigerant
oil specifications.
SPECIFICATIONS - CHARGE CAPACITY
The R-134a refrigerant system charge capacity for
this vehicle is: 0.7371 Kg. (26 oz.).
A/C COMPRESSOR
DESCRIPTION
DESCRIPTION
The air conditioning system uses a Sanden SD-7
reciprocating swash plate-type compressor on all
models. This compressor has a fixed displacement of
165 cubic centimeter and has both the suction and
discharge ports located on the cylinder head. A label
identifying the use of R-134a refrigerant is located on
the compressor.
DESCRIPTION - HIGH PRESSURE RELIEF
VALVE
A high pressure relief valve is located on the com-
pressor cylinder head, which is on the rear of the
compressor. This mechanical valve is designed to
vent refrigerant from the system to protect against
damage to the compressor and other system compo-
DRPLUMBING 24 - 35
PLUMBING (Continued)

(5) Disconnect the condenser cooling fan electric
connector.
(6) Remove the two nuts that secure the condenser
studs to the upper cross brace. (Fig. 5).
(7) Remove the condenser and fan assembly from
the vehicle.
REMOVAL - 5.9L DIESEL ENGINE
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
(1) Disconnect and isolate the battery negative
cable.
(2) Recover the refrigerant from the refrigerant
system. (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT RECOVERY)
(3) Remove the nut that secures the block fitting
to the stud on the condenser inlet, and disconnect the
discharge line from the condenser. Install plugs in, or
tape over all of the opened refrigerant line fittings.
(4) Disconnect the refrigerant line fitting that
secures the liquid line to the condenser outlet. (Refer
to 24 - HEATING & AIR CONDITIONING/PLUMB-
ING - STANDARD PROCEDURE - A/C LINE COU-PLER) Install plugs in, or tape over all of the opened
refrigerant line fittings.
(5) On diesel engine models:
(a) Remove the two screws that secure the
brackets on the passenger side end of the con-
denser to the charge air cooler (Fig. 6).
(b) Remove the two nuts that secure the driver
side end of the condenser to the studs on the
charge air cooler.
(c) Remove the condenser from the vehicle.
REMOVAL - 8.0L Engine
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN TEH FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION(Refer
to 24 - HEATING & AIR CONDITIONING/PLUMBING -
WARNING) AND (Refer to 24 - HEATING & AIR CON-
DITIONING/PLUMBING - CAUTION).
(1) Remove battery negative cable.
(2) Recover refrigerant from a/c system(Refer to 24
- HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE).
Fig. 5 Condenser Module
1 - Condensor Module Mounting Screw
2 - Front Cross Member
3 - Lower Module Mounting Flang
4 - Fan Assembly Mounting Screw
5 - Fan Assembly Mounting Screw
6 - Condensor Mounting Tabs
7 - Condensor Fan Assembly
8 - Fan Power Connector
9 - Condensor Module Mounting Screw
Fig. 6 CONDENSER - DIESEL ENGINE
1 - Discharge line to condenser
2 - Condensor mounting bolt
3 - Liquid Line
4 - Condenser mounting bolt
5 - A/C condenser
6 - Condenser mounting bolt
7 - Condenser mounting bolt
24 - 40 PLUMBINGDR
A/C CONDENSER (Continued)

AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE - A/C LINE COUPLERS)
(4) Remove the tape or plugs from the refrigerant
line fittings on the condenser inlet and the discharge
line. Connect the discharge line to the condenser
inlet. (Refer to 24 - HEATING & AIR CONDITION-
ING/PLUMBING - STANDARD PROCEDURE - A/C
LINE COUPLERS)
(5) Connect the battery negative cable.
(6) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(7) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
NOTE: If the condenser is replaced, add 30 millili-
ters (1 fluid ounce) of refrigerant oil to the refriger-
ant system. Use only refrigerant oil of the type
recommended for the compressor in the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT OIL - DESCRIPTION)
INSTALLATION - 5.9L DIESEL ENGINE
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)(Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING -
CAUTION - REFRIGERANT HOSES/LINES/TUBES
PRECAUTIONS)
(1) On diesel engine models:
(a) Install the driver side condenser mounting
brackets over the two studs on the charge air
cooler.
(b) Install the two screws that secure the brack-
ets on the passenger side end of the condenser to
the charge air cooler. Tighten the mounting screws
to 10.5 N´m (95 in. lbs.).
(c) Install the two nuts that secure the driver
side end of the condenser to the studs on the
charge air cooler. Tighten the mounting nuts to
10.5 N´m (95 in. lbs.).
(2) Remove the plugs or tape from the refrigerant
line fittings on the liquid line and the condenser out-
let. Connect the liquid line to the condenser outlet.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - STANDARD PROCEDURE - A/C LINE
COUPLERS)(3) Install a new gasket and the discharge line
block fitting over the stud on the condenser inlet.
Tighten the mounting nut to 20 N´m (180 in. lbs.).
(4) Check that all of the condenser and radiator
air seals are in their proper locations.
(5) Connect the battery negative cable.
(6) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(7) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
NOTE: If the condenser is replaced, add 30 millili-
ters (1 fluid ounce) of refrigerant oil to the refriger-
ant system. Use only refrigerant oil of the type
recommended for the compressor in the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT OIL - DESCRIPTION)
INSTALLATION - 8.0L Engine
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION(Refer
to 24 - HEATING & AIR CONDITIONING/PLUMBING -
WARNING) AND (Refer to 24 - HEATING & AIR CON-
DITIONING/PLUMBING - CAUTION).
(1) If the condenser was removed from the shroud,
install it and tighten the mounting screws.
(2) Install the condenser and shroud in the vehicle.
Make sure the lower mounting flanges are positioned
correctly before installing the two mounting screws
to the radiator brace. Tighten the screws to spec.
(3) Remove and plugs or tape installed over the
condenser connections and the a/c lines.
(4) Install the lines to the condenser(Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
DISCHARGE LINE - INSTALLATION) and (Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING/
SUCTION LINE - INSTALLATION).
(5) Install the hood latch assembly(Refer to 23 -
BODY/HOOD/LATCH - INSTALLATION).
(6) Install the front bumper assembly(Refer to 13 -
FRAME & BUMPERS/BUMPERS/FRONT BUMPER
- INSTALLATION).
(7) Evacuate the a/c system(Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - STAN-
DARD PROCEDURE).
24 - 42 PLUMBINGDR
A/C CONDENSER (Continued)

small amount of R-12 added to an R-134a refrigerant
system will cause compressor failure, refrigerant oil
sludge or poor air conditioning system performance.
In addition, the PolyAlkylene Glycol (PAG) synthetic
refrigerant oils used in an R-134a refrigerant system
are not compatible with the mineral-based refriger-
ant oils used in an R-12 refrigerant system.
R-134a refrigerant system service ports, service
tool couplers and refrigerant dispensing bottles have
all been designed with unique fittings to ensure that
an R-134a system is not accidentally contaminated
with the wrong refrigerant (R-12). There are also
labels posted in the engine compartment of the vehi-
cle and on the compressor identifying to service tech-
nicians that the air conditioning system is equipped
with R-134a.
DIAGNOSIS AND TESTING- REFRIGERANT
SYSTEM LEAKS
WARNING: (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - WARNING) and (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING - CAU-
TION).
If the air conditioning system does not cool prop-
erly, the A/C system performance should be tested.
See A/C Performance in the Diagnosis and Testing
section of this group for the procedures. If the A/C
system refrigerant fill is found to be low or if the sys-
tem is empty; a leak at a refrigerant line, connector
fitting, component, or component seal is likely.
An electronic leak detector designed for R-134a
refrigerant, or a fluorescent R-134a leak detection
dye and a black light are recommended for locating
and confirming refrigerant system leaks. Refer to the
operating instructions supplied by the equipment
manufacturer for the proper care and use of this
equipment.
An oily residue on or near refrigerant system lines,
connector fittings, components, or component seals
can indicate the general location of a possible refrig-
erant leak. However, the exact leak location should
be confirmed with an electronic leak detector prior to
component repair or replacement.
To detect a leak in the refrigerant system with an
electronic leak detector, perform one of the following
procedures:
SYSTEM EMPTY
(1) Evacuate the refrigerant system (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/RE-
FRIGERANT - STANDARD PROCEDURE).
(2) Connect and dispense 0.283 kilograms (0.625
pounds or 10 ounces) of R-134a refrigerant into the
evacuated refrigerant system (Refer to 24 - HEAT-ING & AIR CONDITIONING/PLUMBING/REFRIG-
ERANT - STANDARD PROCEDURE).
(3) Position the vehicle in a wind-free work area.
This will aid in detecting small leaks.
(4) With the engine not running, use a electronic
R-134a leak detector and search for leaks. Because
R-134a refrigerant is heavier than air, the leak detec-
tor probe should be moved slowly along the bottom
side of all refrigerant lines, connector fittings and
components.
(5) To inspect the evaporator coil for leaks, insert
the electronic leak detector probe into the center
instrument panel outlet and the floor duct outlet. Set
the blower motor switch to the lowest speed position,
and the mode control switch in the recirculation
mode (Max-A/C).
SYSTEM LOW
(1) Position the vehicle in a wind-free work area.
This will aid in detecting small leaks.
(2) Bring the refrigerant system up to operating
temperature and pressure. This is done by allowing
the engine to run with the air conditioning system
turned on for five minutes.
(3) With the engine not running, use a electronic
R-134a leak detector and search for leaks. Because
R-134a refrigerant is heavier than air, the leak detec-
tor probe should be moved slowly along the bottom
side of all refrigerant lines, connector fittings and
components.
(4) To inspect the evaporator coil for leaks, insert
the electronic leak detector probe into the center
instrument panel outlet and the floor duct outlet. Set
the blower motor switch to the lowest speed position,
and the mode control switch in the recirculation
mode (Max-A/C).
STANDARD PROCEDURE
STANDARD PROCEDURE - REFRIGERANT
SYSTEM EVACUATE
WARNING: (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - WARNING) AND (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING - CAU-
TION) BEFORE PERFORMING THE FOLLOWING
OPERATION.
If the refrigerant system has been open to the
atmosphere, it must be evacuated before the system
can be charged. If moisture and air enters the system
and becomes mixed with the refrigerant, the com-
pressor head pressure will rise above acceptable
operating levels. This will reduce the performance of
the air conditioner and could damage the compressor.
Evacuating the refrigerant system will remove the
DRPLUMBING 24 - 51
REFRIGERANT (Continued)

EMISSIONS CONTROL
TABLE OF CONTENTS
page page
EMISSIONS CONTROL
DESCRIPTION
DESCRIPTION - STATE DISPLAY TEST
MODE...............................1
DESCRIPTION - CIRCUIT ACTUATION TEST
MODE...............................1
DESCRIPTION - DIAGNOSTIC TROUBLE
CODES..............................1
DESCRIPTION - TASK MANAGER..........1DESCRIPTION - MONITORED SYSTEMS....1
DESCRIPTION - TRIP DEFINITION.........4
DESCRIPTION - COMPONENT MONITORS . . 4
OPERATION
OPERATION..........................4
OPERATION - TASK MANAGER...........5
OPERATION - NON-MONITORED CIRCUITS . . 8
EVAPORATIVE EMISSIONS................10
EMISSIONS CONTROL
DESCRIPTION
DESCRIPTION - STATE DISPLAY TEST MODE
The switch inputs to the Powertrain Control Mod-
ule (PCM) have two recognized states; HIGH and
LOW. For this reason, the PCM cannot recognize the
difference between a selected switch position versus
an open circuit, a short circuit, or a defective switch.
If the State Display screen shows the change from
HIGH to LOW or LOW to HIGH, assume the entire
switch circuit to the PCM functions properly. Connect
the DRB scan tool to the data link connector and
access the state display screen. Then access either
State Display Inputs and Outputs or State Display
Sensors.
DESCRIPTION - CIRCUIT ACTUATION TEST
MODE
The Circuit Actuation Test Mode checks for proper
operation of output circuits or devices the Powertrain
Control Module (PCM) may not internally recognize.
The PCM attempts to activate these outputs and
allow an observer to verify proper operation. Most of
the tests provide an audible or visual indication of
device operation (click of relay contacts, fuel spray,
etc.). Except for intermittent conditions, if a device
functions properly during testing, assume the device,
its associated wiring, and driver circuit work cor-
rectly. Connect the DRB scan tool to the data link
connector and access the Actuators screen.
DESCRIPTION - DIAGNOSTIC TROUBLE CODES
A Diagnostic Trouble Code (DTC) indicates the
PCM has recognized an abnormal condition in the
system.Remember that DTC's are the results of a sys-
tem or circuit failure, but do not directly iden-
tify the failed component or components.
BULB CHECK
Each time the ignition key is turned to the ON
position, the malfunction indicator (check engine)
lamp on the instrument panel should illuminate for
approximately 2 seconds then go out. This is done for
a bulb check.
OBTAINING DTC'S USING DRB SCAN TOOL
(1) Obtain the applicable Powertrain Diagnostic
Manual.
(2) Obtain the DRB Scan Tool.
(3) Connect the DRB Scan Tool to the data link
(diagnostic) connector. This connector is located in
the passenger compartment; at the lower edge of
instrument panel; near the steering column.
(4) Turn the ignition switch on and access the
ªRead Faultº screen.
(5) Record all the DTC's and ªfreeze frameº infor-
mation shown on the DRB scan tool.
(6) To erase DTC's, use the ªErase Trouble Codeº
data screen on the DRB scan tool.Do not erase any
DTC's until problems have been investigated
and repairs have been performed.
DESCRIPTION - TASK MANAGER
The PCM is responsible for efficiently coordinating
the operation of all the emissions-related compo-
nents. The PCM is also responsible for determining if
the diagnostic systems are operating properly. The
software designed to carry out these responsibilities
is call the 'Task Manager'.
DESCRIPTION - MONITORED SYSTEMS
There are new electronic circuit monitors that
check fuel, emission, engine and ignition perfor-
DREMISSIONS CONTROL 25 - 1

pump by drawing air into the pump cavity and also
closes the vent seal. During non test conditions the
vent seal is held open by the pump diaphragm
assembly which pushes it open at the full travel posi-
tion. The vent seal will remain closed while the
pump is cycling due to the reed switch triggering of
the three port solenoid that prevents the diaphragm
assembly from reaching full travel. After the brief
initialization period, the solenoid is de-energized
allowing atmospheric pressure to enter the pump
cavity, thus permitting the spring to drive the dia-
phragm which forces air out of the pump cavity and
into the vent system. When the solenoid is energized
and de energized, the cycle is repeated creating flow
in typical diaphragm pump fashion. The pump is con-
trolled in 2 modes:
Pump Mode: The pump is cycled at a fixed rate to
achieve a rapid pressure build in order to shorten the
overall test length.
Test Mode: The solenoid is energized with a fixed
duration pulse. Subsequent fixed pulses occur when
the diaphragm reaches the Switch closure point.
The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5º H20.
The cycle rate of pump strokes is quite rapid as the
system begins to pump up to this pressure. As the
pressure increases, the cycle rate starts to drop off. If
there is no leak in the system, the pump would even-
tually stop pumping at the equalized pressure. If
there is a leak, it will continue to pump at a rate rep-
resentative of the flow characteristic of the size of the
leak. From this information we can determine if the
leak is larger than the required detection limit (cur-
rently set at .040º orifice by CARB). If a leak is
revealed during the leak test portion of the test, the
test is terminated at the end of the test mode and no
further system checks will be performed.
After passing the leak detection phase of the test,
system pressure is maintained by turning on the
LDP's solenoid until the purge system is activated.
Purge activation in effect creates a leak. The cycle
rate is again interrogated and when it increases due
to the flow through the purge system, the leak check
portion of the diagnostic is complete.
The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
Evaporative system functionality will be verified by
using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to
seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a
shift in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test is
passed. If not, it is assumed that the purge system isnot functioning in some respect. The LDP is again
turned off and the test is ended.
MISFIRE MONITOR
Excessive engine misfire results in increased cata-
lyst temperature and causes an increase in HC emis-
sions. Severe misfires could cause catalyst damage.
To prevent catalytic convertor damage, the PCM
monitors engine misfire.
The Powertrain Control Module (PCM) monitors
for misfire during most engine operating conditions
(positive torque) by looking at changes in the crank-
shaft speed. If a misfire occurs the speed of the
crankshaft will vary more than normal.
FUEL SYSTEM MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide. The catalyst works best
when the Air Fuel (A/F) ratio is at or near the opti-
mum of 14.7 to 1.
The PCM is programmed to maintain the optimum
air/fuel ratio of 14.7 to 1. This is done by making
short term corrections in the fuel injector pulse width
based on the O2S sensor output. The programmed
memory acts as a self calibration tool that the engine
controller uses to compensate for variations in engine
specifications, sensor tolerances and engine fatigue
over the life span of the engine. By monitoring the
actual fuel-air ratio with the O2S sensor (short term)
and multiplying that with the program long-term
(adaptive) memory and comparing that to the limit,
it can be determined whether it will pass an emis-
sions test. If a malfunction occurs such that the PCM
cannot maintain the optimum A/F ratio, then the
MIL will be illuminated.
CATALYST MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide.
Normal vehicle miles or engine misfire can cause a
catalyst to decay. This can increase vehicle emissions
and deteriorate engine performance, driveability and
fuel economy.
The catalyst monitor uses dual oxygen sensors
(O2S's) to monitor the efficiency of the converter. The
dual O2S's sensor strategy is based on the fact that
as a catalyst deteriorates, its oxygen storage capacity
and its efficiency are both reduced. By monitoring
the oxygen storage capacity of a catalyst, its effi-
ciency can be indirectly calculated. The upstream
O2S is used to detect the amount of oxygen in the
exhaust gas before the gas enters the catalytic con-
DREMISSIONS CONTROL 25 - 3
EMISSIONS CONTROL (Continued)