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HVAC - SERVICE INFORMATION
DESCRIPTION ............................... 209
OPERATION ................................. 209
DIAGNOSIS AND TESTING
HEATING-A/C SYSTEM DIAGNOSTICS ...... 211
A/C PERFORMANCE ....................... 212
HEATER PERFORMANCE .................. 215
SPECIFICATIONS
A/C SYSTEM .............................. 216TORQUE .................................. 216
SPECIAL TOOLS
A/C SYSTEM .............................. 218
CONTROLS............................219
DISTRIBUTION.........................253
PLUMBING............................284
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HVAC - SERVICE INFORMATION
DESCRIPTION
A manually controlled single zone type heating-air conditioning system or a manually controlleddualzonetypeheat-
ing-air conditioning system is available on this model.
To maintain the performance level of the heating, ventilation and air conditioning (HVAC) system, the engine cooling
system must be properly maintained. The use of a bug screen is not recommended. Any obstructions in front of the
radiator or A/C condenser will reduce the performance of the A/C and enginecooling systems.
The engine cooling system includes the radiator, thermostat, radiator hoses and the engine coolant pump. Refer to
7 - Cooling for more information before opening or attempting any service to the engine cooling system.
All vehicles are equipped with a common heater, ven-
tilation and air conditioning (HVAC) housing (1). The
system combines air conditioning, heating, and venti-
lating capabilities in a single unit housing mounted
within the passenger compartment under the instru-
ment panel. The HVAC housing includes:
Blend-air door(s) and actuator(s) (2)
Recirculation-air door and actuator (3)
A/C evaporator (4)
Blower motor (5)
Blower motor resistor (6)
Evaporator temperature sensor (7)
Heater core (8)
Mode-air doors and actuators (9)
Based upon the system and mode selected, conditioned air can exit the HVAC housing through one or a combi-
nation of the three main housing outlets: defrost, panel or floor. The defrost and the panel outlets are located on the
top of the housing and, the floor outlet is located on the bottom of the housing. Once the conditioned air exits the
HVAC housing, it is further directed through molded plastic ducts to the various outlets within the vehicle interior.
These outlets and their locations are as follows:
Defroster Outlet- A single large defroster outlet is located in the center of the instrumentpanel top cover,
near the base of the windshield.
Side Window Demister Outlets- There are two side window demister outlets, one is located at each out-
board end of the instrument panel top cover, near the belt line at the A-pillars.
Panel Outlets- There are four panel outlets in the instrument panel, one located near each outboard end of
the instrument panel facing the rear of the vehicle and two located near thetop of the instrument panel center
bezel.
Front Floor Outlets- There are two front floor outlets, one located above each side of the floorpanel center
tunnel near the dash panel.
Rear Outlets- On Mega Cab models there are two outlets located at the rear of the center front seat.
OPERATION
Both the manual temperature control (MTC) single zone and dual zone heating-A/C system are blend-air type sys-
tems. In a blend-air heating-A/C, a blend-air door controls the amount of conditioned air that is allowed to flow
through, or around, the heater core.In the available dual zone system, twoblend-air doors are used to provide
completely independent side-to-side temperature control of the discharge air. The temperature control(s) determines
the discharge air temperature(s) by operating the blend door actuator(s), which move the blend-air door(s). This
design allows almost immediate control of output air temperature(s).
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The heating-A/C systems pulls outside (ambient) air
through the cowl opening at the base of the wind-
shield, then into the air inlet housing above the heat-
ing, ventilation and air conditioning (HVAC) housing.
On models equipped with A/C, the air passes through
the A/C evaporator (3). Air flow can be directed either
through or around the heater core (1). This is done by
adjusting the blend-air door(s) (2) with the temperature
control(s) located on the A/C-heater control in the
instrument panel. The air flow can then be directed
from the panel, floor and defrost outlets in various
combinations using the mode control located on the A/C-heater control. Air flow velocity can be adjusted with the
blower speed control located on the A/C-heater control.
On all models, the outside air intake can be shut off by selecting the Recirculation Mode with the mode control. This
will operate a electrically actuated recirculation-air door (4) that closes off the fresh air intake and recirculates the air
that is already inside the vehicle.
On models with A/C, the A/C compressor can be engaged in any mode by pressingthe snowflake, A/C on/off but-
ton. It can also be engaged by placing the mode control in the mix to defrost positions. This will remove heat and
humidity from the air before it is directed through or around the heater core. The mode control on the A/C-heater
control is used to also direct the conditioned air to the selected system outlets. The mode control uses electric
actuators to control the mode-air doors (5 and 6).
The defroster outlet receives airflow from the HVAC housing through the molded plastic defroster duct, which con-
nects to the HVAC housing defroster outlet. The airflow from the defrosteroutlets is directed by fixed vanes in the
defroster outlet grilles and cannot be adjusted. The defroster outlet grilles are integral to the instrument panel top
cover.
The side window demister outlets receive airflow from the HVAC housing through the molded plastic defroster duct
and two molded plastic demister ducts. The airflow from the side window demister outlets is directed by fixed vanes
in the demister outlet grilles and cannot be adjusted. The side window demister outlet grilles are integral to the
instrument panel. The demisters direct air from the HVAC housing through the outlets located on the top corners of
the instrument panel. The demisters operate when the mode control knob is positioned in the floor-defrost and
defrost-only settings. Some air may be noticeable from the demister outlets when the mode control is in the bi-level
to floor positions.
The panel outlets receive airflow from the HVAC housing through a molded plastic main panel duct, center panel
duct and two end panel ducts. The two end panel ducts direct airflow to the left and right instrument panel outlets,
while the center panel duct directs airflow to the two center panel outlets. Each of these outlets can be individually
adjusted to direct the flow of air.
The floor outlets receive airflow from the HVAC housing through the floor distribution duct. The front floor outlets are
integral to the molded plastic floor distribution duct, which is secured to the bottom of the housing. The floor outlets
cannot be adjusted.
NOTE: It is important to keep the air intake opening clear of debris. Leaf particles and other debris that is
small enough to pass through the cowl opening screen can accumulate withinthe HVAC housing. The
closed, warm, damp and dark environment created within the housing is ideal for the growth of certain
molds, mildews and other fungi. Any accumulation of decaying plant matterprovides an additional food
source for fungal spores, which enter the housing with the fresh intake-air. Excess debris, as well as objec-
tionable odors created by decaying plant matter and growing fungi can be discharged into the passenger
compartment during heater-A/C operation if the air intake opening is not kept clear of debris.
The A/C system on models so equipped is designed for the use of non-CFC, R-134a refrigerant and uses an A/C
fixedorificetubelocatedintheliquidlinetometertheflowofrefrigerant to the A/C evaporator. The A/C evaporator
cools and dehumidifies the incoming air prior to blending it with the heated air. To maintain minimum evaporator
temperature and prevent evaporator freezing, an evaporator temperaturesensor is used to supply evaporator tem-
perature input to the A/C-heater control. The powertrain control module (PCM) cycles the A/C compressor clutch off
and on as necessary to protect the A/C system from evaporator freezing and optimize A/C system performance.
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DIAGNOSIS AND TESTING
HEATING-A/C SYSTEM DIAGNOSTICS
CAUTION: Do not exchange A/C Heater Controls from vehicle to vehicle. Software versions differ between
models and model years. Installing an A/C Heater Control with software that is incompatible for a given
vehicle can result in either improper or failed HVAC system operation.
ON-BOARD DIAGNOSTICS
The A/C-heater control communicates on the controller area network (CAN)B bus and is fully addressable with a
scan tool.
The A/C-heater control’s primary means of fault detection is through active and stored diagnostic trouble codes
(DTCs). Active DTCs are those which currently exist in the system. The condition causing the fault must be repaired
in order to clear this type of DTC. Stored DTCs are those which occurred in the system since the A/C-heater control
received the last clear diagnostic info message. DTCs must be read with a scan tool. Refer to 24 - HVAC - Elec-
trical Diagnostics for HVAC DTC diagnostic test procedures.
The A/C-heater control’s secondary means of fault detection is through system tests. These tests include the HVAC
System Test, the A/C Cooldown Test, Actuator Calibration, and Actuator DTC Detection. Refer to System Tests in
this Section for a detailed description of each test.
SYSTEM TESTS
HVAC System Test
The HVAC System Test, found in 24 - HVAC - Electrical Diagnostics, providesa starting point in the diagnostic
process by identifying the appropriate diagnostic procedure or system test to perform when diagnosing a given
symptom, condition, or DTC. It also provides a means for testing the entireHVAC system by utilizing the A/C-heater
control’s On-Board System Tests. The On-Board System Tests can also assistindiagnosingstoredDTCs.
A/CCOOLDOWNTEST
The A/C Cooldown Test:
is actuated with a scan tool.
tests A/C system performance based on evaporator temperature sensor input.
will fail if evaporator temperature isbelow 13°C (55°F) when initiating the test.
will pass if the evaporator temperature drops 11°C (20°F).
indicates an outcome by displaying one or more test status messages on the scan tool. These test status
messages will clear after paging back out of this test function. Therefore, is it important to note all of the mes-
sages before doing so.
will cause the A/C status indicator to flash while the test is running.
ACTUATOR CALIBRATION FUNCTION
The Actuator Calibration function:
is actuated with a scan tool.
clears all actuator related DTCs when the test is actuated.
homes and repositions door actuators.
monitors for door span faults. Door span faults (XXX Door Travel Range Too Large or XXX Door Travel Range
Too Small) will only display after calibration.
will cause the electric backlight (EBL) status indicator (if equipped) toflash while the test is running.
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ACTUATOR DTC DETECTION TEST — DUAL-ZONE
The Actuator DTC Detection Test:
is actuated with a scan tool.
clears all actuator related DTCs when the test is actuated.
supplements the continuous diagnostics on the actuator drive system.
monitors for shorted actuator circuits allowing service to easily diagnose and troubleshoot up to three simul-
taneous shorts. Shorted actuator circuit faults (XXX Control Circuit High or XXX Control Circuit Low) will only
display after running the Actuator DTC Detection Test.
After repairing each DTC, cycle the ignition switch, and then run the Actuator DTC Detection Test again to ensure
that no new DTCs exist. If multiple DTCs are present, beginning with the passenger blend door, diagnose and repair
all short high faults and then short low faults. When the test returns passed, clear all faults and run the Actuator
Calibration function as a final check of system health.
ACTUATOR DTC DETECTION TEST — SINGLE-ZONE
The Actuator DTC Detection Test:
is actuated with a scan tool.
clears all actuator related DTCs when the test is actuated.
supplements the continuous diagnostics on the actuator drive system.
monitors for shorted actuator circuits allowing service to easily diagnose and troubleshoot up to three simul-
taneous shorts. Shorted actuator circuit faults (XXX Control Circuit High or XXX Control Circuit Low) will only
display after running the Actuator DTC Detection Test.
After repairing each DTC, cycle the ignition switch, and then run the Actuator DTC Detection Test again to ensure
that no new DTCs exist. If multiple DTCs are present, beginning with the common circuit, diagnose and repair all
short high faults and then short low faults. When the test returns passed, clear all faults and run the Actuator Cal-
ibration function as a final check of system health.
A/C PERFORMANCE
The A/C system is designed to provide the passenger compartment with low temperature and low humidity air. The
A/C evaporator, located in the HVAC housing is cooled to temperatures nearthe freezing point. As warm damp air
passes over the fins of the A/C evaporator, the air transfers its heat to therefrigerant in the evaporator coils and the
moisture in the air condenses on the evaporator fins. During periods of high heat and humidity, an A/C system will
be more effective in the Recirculation mode (max-A/C). With the system in the Recirculation mode, only air from the
passenger compartment passes through the A/C evaporator. As the passenger compartment air dehumidifies, the
A/C system performance levels rise.
Humidity has an important bearing on the temperature of the air delivered to the interior of the vehicle. It is impor-
tant to understand the effect that humidity has on the performance of the A/C system. When humidity is high, the
A/C evaporator has to perform a double duty. It must lower the air temperature, and it must lower the temperature
of the moisture in the air that condenses on the evaporator fins. Condensing the moisture in the air transfers heat
energy into the evaporator fins and coils. This reduces the amount of heat the A/C evaporator can absorb from the
air. High humidity greatly reduces the ability of the A/C evaporator to lower the temperature of the air.
However, evaporator capacity used to reduce the amount of moisture in the air is not wasted. Wringing some of the
moisture out of the air entering the vehicle adds to the comfort of the passengers. Although, an owner may expect
too much from their A/C system on humid days. A performance test is the best way to determine whether the sys-
tem is performing up to design standards. This test also provides valuableclues as to the possible cause of trouble
with the A/C system. The ambient air temperature in the location where the vehicle will be tested must be a mini-
mum of 21° C (70° F) for this test.
A/C PERFORMANCE TEST
WARNING: Refer to the applicable warnings and cautions for this system before performing the following
operation (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - WARNINGS) and (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - CAUTIONS). Failure to follow the warnings and cautions could result
in possible personal injury or death.
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NOTE: When connecting the service equipment coupling to the line fitting,verify that the valve of the cou-
pling is fully closed. This will reduce the amount of effort required to make the connection.
NOTE: The work area ambient temperature must be above 21° C (70° F) and the evaporator temperature
must be above 13° C (55° F) prior to conducting the A/C Performance Test.
1. Conduct the A/C System Performance Test (Cooldown Test) found within the HVAC System Test (refer to 24 -
HVAC Electrical Diagnostics). If no diagnostic trouble codes (DTCs) are found in the A/C-heater control, power-
train control module (PCM) or engine control module (ECM) (depending on engine application), gateway module
or the totally integrated power module (TIPM), go to Step 2. If any DTCs are found, repair as required, then
proceedtoStep2.
2. Connect a tachometer and a manifold gauge set or an A/C recycling/charging station.
3. Operate the heating-A/C system under the following conditions.
Engine at 1,000 rpm at operating temperature
Door or windows open
Transmission in Park or Neutral with parking brake set (depending on application)
A/C-heater controls set to Recirculation mode (max-A/C), full cool, panel mode, high blower and with A/C com-
pressor engaged. If the A/C compressor does not engage, see the A/C System Diagnosis chart.
4. Insert a thermometer in the driver side center panel air outlet and operate the A/C system until the thermometer
temperature stabilizes.
5. With the A/C compressor clutch engaged, compare the air temperature at the center panel outlet and the A/C
compressor discharge pressure (high side) to the A/C Performance Temperature and Pressure chart. The com-
pressor clutch may cycle, depending upon the ambient temperature and humidity. If the clutch cycles, use the
readings obtained before the clutch disengaged.
A/C PERFORMANCE TEMPERATURE AND PRESSURE
Ambient Air
Temperature21° C
(70° F)27° C
(80° F)32° C
(90° F)38° C
(100° F)43° C
(110° F)
Air Temperature at
Center Panel Outlet7° C
(45° F)7° C
(45° F)13° C
(55° F)13° C
(55° F)18° C
(64° F)
Compressor Inlet
Pressure at Service
Port (low Side)138 to 207 kPa
(20to30psi)172to241kPa
(25to35psi)207 to 276
kPa
(30to40psi)241 to 310
kPa
(35to45psi)276to345kPa
(40to50psi)
Compressor
Discharge Pressure at
Service Port (High
Side)1034 to 1724
kPa
(150 to 250
psi)1379to2068
kPa
(200 to 300
psi)1724to2413
kPa
(250 to 350
psi)1999 to 2689
kPa
(290 to 390
psi)2413to2965
kPa
(350 to 430 psi)
6. If the air outlet temperature fails to meet the specifications in the A/CPerformance Temperature and Pressure
chart, or if the A/C compressor discharge pressure is high, refer to the A/CSystem Diagnosis chart.
A/C SYSTEM DIAGNOSIS
Condition Possible Causes Correction
Constant compressor
engagement and warm air
from passenger vents.1. Low refrigerant system
charge.1. See Refrigerant System Leaks in this group.
Test the refrigerant system for leaks. Repair,
evacuate and charge the refrigerant system, if
required.
Equal pressures, but the
compressor clutch does not
engage.1. No refrigerant in the
refrigerant system.1. See Refrigerant System Leaks in this group.
Test the refrigerant system for leaks. Repair,
evacuate and charge the refrigerant system, if
required.
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Condition Possible Causes Correction
2. Faulty fuse.2. Check the fuse in the junction block. Repair the
shorted circuit or component and replace the fuse,
if required.
3. Faulty A/C compressor
clutch field coil.3. See A/C Compressor Clutch Field Coil in this
group. Test the compressor clutch field coil and
replace, if required.
4. Improperly installed or
faulty Evaporator
Temperature Sensor.4. See Evaporator Temperature Sensor in this
group. Correctly install or replace the sensor as
required.
5. Faulty A/C pressure
transducer.5. See A/C pressure transducer in this group. Test
the transducer and replace, if required.
6. Faulty A/C-heater control,
totally integrated power
module (TIPM), gateway
module or PCM/ECM.6. Refer to the appropriate Electrical Diagnostic
Procedures for testing of the A/C-heater control,
TIPM, gateway module or PCM/ECM. Test the
module and replace, if required.
Normal pressures, but A/C
Performance Test air
temperatures at center panel
outlet are too high.1. Excessive refrigerant oil in
system.1. See Refrigerant Oil Level in this group. Recover
the refrigerant from the refrigerant system and
inspect the refrigerant oil content. Restore the
refrigerant oil to the proper level, if required.
2. Blend door inoperative or
sealing improperly.2. See Blend Door in this group. Inspect the blend
door for proper operation and sealing and correct,
if required.
3. Blend door actuator faulty
or inoperative.3. Perform blend door actuator diagnosis, replace
if faulty.
The low side pressure is
normal or slightly low, and
the high side pressure is too
low.1. Low refrigerant system
charge.1. See Refrigerant System Leaks in this group.
Test the refrigerant system for leaks. Repair,
evacuate and charge the refrigerant system, if
required.
2. Refrigerant flow through
the accumulator is restricted.2. See Accumulator in this group. Replace the
restricted accumulator, if required.
3. Refrigerant flow through
the evaporator coil is
restricted.3. See A/C Evaporator in this group. Replace the
restricted evaporator coil, if required.
4. Faulty compressor.4. See A/C Compressor in this group. Replace the
compressor, if required.
The low side pressure is
normal or slightly high, and
the high side pressure is too
high.1. Condenser air flow
restricted.1. Check the A/C condenser for damaged fins,
foreign objects obstructing air flow through the
condenser fins, and missing or improperly
installed air seals. Refer to Cooling for more
information on air seals. Clean, repair, or replace
components as required.
2. Inoperative cooling fan.2. Refer to Cooling for more information. Test the
cooling fan and replace, if required.
3. Refrigerant system
overcharged.3. See Refrigerant System Charge in this group.
Recover the refrigerant from the refrigerant
system. Charge the refrigerant system to the
proper level, if required.
4. Air in the refrigerant
system.4. See Refrigerant System Leaks in this group.
Test the refrigerant system for leaks. Repair,
evacuate and charge the refrigerant system, if
required.
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Condition Possible Causes Correction
5. Engine overheating.5. Refer to Cooling for more information. Test the
cooling system and repair, if required.
The low side pressure is too
high, and the high side
pressure is too low.1. Accessory drive belt
slipping.1. Refer to Cooling for more information. Inspect
the accessory drive belt condition and tension.
Tighten or replace the accessory drive belt, if
required.
2. Fixed orifice tube not
installed.2. See A/C Orifice Tube in this group. Replace the
liquid line, if required.
3. Faulty A/C compressor.3. See A/C Compressor in this group. Replace the
compressor, if required.
The low side pressure is too
low, and the high side
pressure is too high.1. Restricted refrigerant flow
through the refrigerant lines.1. See Liquid, Suction, and Discharge Line in this
group. Inspect the refrigerant lines for kinks, tight
bends or improper routing. Correct the routing or
replace the refrigerant line, if required.
2. Restricted refrigerant flow
through the fixed orifice
tube.2. See A/C Orifice Tube in this group. Replace the
liquid line, if required.
3. Restricted refrigerant flow
through the condenser.3. See A/C Condenser in this group. Replace the
restricted condenser, if required.
HEATER PERFORMANCE
Before performing the following tests, refer to Group 7 - Cooling for the procedures to check the engine coolant
level and flow, engine coolant reserve/recovery system operation, accessory drive belt condition and tension, radi-
ator air flow and the fan drive operation. Perform the HVAC System Test (refer to 24 - HVAC Electrical Diagnostics).
If any diagnostic trouble codes (DTCs) are found in the A/C-heater control, powertrain control module (PCM) or
engine control module (ECM) (depending on engine application), gateway module or totally integrated power module
(TIPM), repair as necessary.
MAXIMUM HEATER OUTPUT: TEST AND ACTION
Engine coolant is provided to the heater system through two heater hoses. With the engine idling at normal oper-
ating temperature, set the temperature control to maximum heat position,the mode control to the floor position, and
the blower motor control to the highest speed position. Using a test thermometer, check the temperature of the air
being discharged from the floor outlets. Compare the test thermometer reading to the Heater Temperature Refer-
ence chart.
HEATER TEMPERATURE REFERENCE
Ambient Air Temperature16° C
(60° F)21° C
(70° F)26° C
(80° F)32° C
(90° F)
Minimum Air Temperature at
Floor Outlet62° C
(144° F)64° C
(147° F)65° C
(150° F)67° C
(153° F)
If the heater outlet air temperature is below the minimum specification, refer to Group 7 - Cooling. Both of the heater
hoses should be hot to the touch. The coolant return heater hose should be slightly cooler than the coolant supply
heater hose. If the return hose is much cooler than the supply hose, locate and repair the engine coolant flow
obstruction in the cooling system. RefertoGroup7-Coolingformoreinformation.
OBSTRUCTED COOLANT FLOW
Possible locations or causes of obstructed coolant flow are as follows:
Faulty water pump.
Faulty thermostat.
Pinched or kinked heater hoses.