Page 2265 of 2339

The supplemental cabin heater only operates when
the engine is running, the mileage exceeds 8 kilome-
ter (5 mph) and the fuel tank volume exceeds 1/8 of a
tank. The supplemental heater control module moni-
tors blower speed and combustion during its start-up.
The cabin heater should operate if the coolant tem-
perature is below 40É C (104É F).
AUTOMATIC TEMPERATURE CONTROL
SYSTEM
The automatic temperature control (ATC) system
will activate the supplemental cabin heater based on
engine coolant temperature and interior component
settings. The cabin heater can operate in a full or
partial load range as well as an idle mode all depen-
dent on the engine coolant temperature. The cabin
heater will also turn off if the A/C-heater tempera-
ture control is lowered to less than the lower set
point. The cabin heater can take up to three minutes
to completely shut down when either the heater tem-
perature is set below the lower set point or the vehi-
cle ignition is shut down.
NOTE: Do not apply a strong vacuum source such
as a garage ventilation system directly on the sup-
plemental cabin heater exhaust line. Too strong of a
vacuum can prevent the supplemental cabin heater
from starting. If required, place the vacuum source
at least 75 mm (3 in.) away from the exhaust line.
The supplemental cabin heater only operates when
the engine is running, the mileage exceeds 8 kilome-ter (5 mph) and the fuel tank volume exceeds 1/8 of a
tank. The supplemental heater control module moni-
tors blower speed and combustion during its start-up.
The cabin heater should operate if the coolant tem-
perature is below 40É C (104É F).
WARNING
WARNING: DO NOT OPERATE THE DIESEL SUP-
PLEMENTAL CABIN HEATER IN AN ENCLOSED
AREA SUCH AS A GARAGE THAT DOES NOT HAVE
EXHAUST VENTILATION FACILITIES. ALWAYS VENT
THE CABIN HEATER EXHAUST WHEN OPERATING
THE CABIN HEATER. ALLOW THE DIESEL SUPPLE-
MENTAL CABIN HEATER TO COOL BEFORE PER-
FORMING ANY SERVICE PROCEDURES TO THE
CABIN HEATER. VERIFY THAT ALL DIESEL SUP-
PLEMENTAL CABIN HEATER FUEL LINES ARE
SECURELY FASTENED TO THEIR RESPECTIVE
COMPONENTS BEFORE PERFORMING ANY SER-
VICE PROCEDURES TO THE CABIN HEATER. FAIL-
URE TO FOLLOW THESE INSTRUCTION MAY
RESULT IN PERSONAL INJURY OR DEATH.
DIAGNOSIS AND TESTING
SUPPLEMENTAL CABIN HEATER
Refer to the Symptoms Diagnosis table for basic
checks of the diesel fueled supplemental cabin heater.
SYMPTOMS DIAGNOSIS
Symptom Possible Causes
Smell of diesel fuel. Check cabin heater system integration in vehicle's fuel system. Check
fuel lines for leakage, kinks or obstructions. If OK, Inspect the inlet
muffler, drain as necessary. Re-test the cabin heater and re-inspect.
Inspect the exhaust tube and cabin heater for the presence of external
fuel. If presence of external fuel is observed on the heater unit or in the
exhaust tube or after draining and testing. Remove the cabin heater
from vehicle and repair or replace components as required.
Heater does not achieve full load
operation.Check cabin heater operation with DRBIIITscan tool and replace
components as required.
Continuous white smoke from heater
exhaust during combustion operation.Check cabin heater operation with DRBIIITscan tool and replace
components as required. White smoke is typical in extreme weather
conditions.
Heater can not be switched off. Check cabin heater operation with DRBIIITscan tool and replace
components as required.
Heater does not operate. Diagnosis cabin heater control module using the DRBIIITscan tool and
the procedures listed in Vehicle Performance under Cabin Heater
Diagnosis in Group 18.
24 - 114 CABIN HEATERRS
CABIN HEATER (Continued)
Page 2266 of 2339

Symptom Possible Causes
Loss of coolant (Leakage) or heater
develops smoke during combustion
operation and exhaust has an
extremely sweet smell.Inspect coolant hoses for leakage, kinks or loose hose connection.
Inspect the exhaust tube assembly for continuous flow, if OK there is an
internal heater leak and cabin heater should be inspected and
components should be replaced as required.
Loss of fuel (dripping). Check cabin heater system integration in vehicles fuel system. Check
fuel line connection for leakage. If OK there is an internal leak and
cabin heater should be inspected and replaced as required.
AIR INTAKE PIPE
REMOVAL
NOTE: The air intake tube for the supplemental
cabin heater is part of an assembly that includes
the heater cooling intake and return pipes. If the
cabin heater air intake tube requires removal or
replacement the entire cabin heater assembly will
require removal or replacement.
(1) Drain the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(2) Remove clamps from the cabin heater tubes at
the lower heater port and the lower EGR connector
which are located under the hood.
(3) Remove the retaining clamp at the cabin
heater air intake muffler connection (Refer to 24 -
HEATING & AIR CONDITIONING/CABIN HEAT-
ER/INLET MUFFLER - REMOVAL).
(4) Remove the clamp at the flexible tube to steel
tube connection (Fig. 1).(5) Remove the two retaining screws and remove
pipe assembly (Fig. 2).
INSTALLATION
(1) Install the air intake pipe assembly and install
the two retaining screws. Tighten the screws to 7
N´m (62 in. lbs.).
(2) Attach the steel tube to the flexible tube and
position and then tighten the retaining clamp
securely.
(3) Install the flexible tube to the cabin heater air
intake muffler and install and tighten the retaining
clamp securely.
(4) Install the cabin heater tubes to the lower
heater connection and the lower EGR cooler connec-
tion and tighten the retaining clamps.
(5) Lower the vehicle.
Fig. 1 Flexible Air Intake Line
1 - CABIN HEATER AND SPLASH SHIELD
2 - DOSING PUMP
3 - DOSING PUMP FUEL LINE
4 - FLEXIBLE AIR INTAKE LINE
5 - CLAMP
6 - STEEL INTAKE PIPE
Fig. 2 Cabin Heater Air Intake And Heater Pipe
Assembly
1 - INTAKE TUBE AIR INTAKE
2 - INTAKE PIPE
3 - RETAINING SCREWS
4 - INTAKE HEATER LINE
5 - RETURN HEATER LINE
RSCABIN HEATER24 - 115
CABIN HEATER (Continued)
Page 2267 of 2339

(6) Refill the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(7) Verify function of the cabin heater.
EXHAUST TUBE
REMOVAL
WARNING: THERE IS A POTENTIAL DANGER OF
SKIN BURNS AS THE SUPPLEMENTAL CABIN
HEATER AND ITS COMPONENTS MAY BE VERY
HOT. MAKE SURE THE CABIN HEATER IS
ALLOWED TO COOL DOWN BEFORE ANY SERVICE
WORK ON THE CABIN HEATER SYSTEM IS
ATTEMPTED.
(1) Raise and support the vehicle. Take note of the
location of the flexible section of the cabin heater
exhaust tube.
(2) Remove the exhaust clamp at the flexible pipe
and steel pipe connection (Fig. 3).
(3) Remove the clamp at the flexible pipe connec-
tion and the cabin heater housing (if required).
(4) Remove the three screws holding the exhaust
pipe to the body.(5) Remove the steel exhaust pipe from the vehi-
cle.
(6) Remove the flexible exhaust pipe from the
vehicle (if required).
INSTALLATION
(1) Install the flexible exhaust pipe to the cabin
heater. Tighten the mounting clamp securely.
(2) Position the steel exhaust pipe to the flexible
exhaust. Tighten the mounting clamp securely.
(3) Loosely install the three exhaust pipe screws
and adjust pipe placement as required. Tighten the
screws securely.
(4) Install the clamp that secures the steel exhaust
pipe to the flexible exhaust pipe. Tighten the clamp
securely.
(5) Check exhaust end placement of the exhaust
pipe and make any final adjustments.
(6) Lower the vehicle.
Fig. 3 Cabin Heater Exhaust System
1 - MOUNTING SCREWS (3)
2 - STEEL HEATER EXHAUST PIPE
3 - EXHAUST CLAMP (2)4 - FLEXIBLE HEATER EXHAUST PIPE
5 - CABIN HEATER AND SHIELD
6 - EXHAUST PIPE MOUNTING CLIPS (3) (IF EQUIPPED)
24 - 116 CABIN HEATERRS
AIR INTAKE PIPE (Continued)
Page 2268 of 2339

FUEL DOSING PUMP
DESCRIPTION
The dosing pump is a combined delivery, dosing
and shut-off system for the fuel supply to the supple-
mental cabin heater from the vehicle fuel tank.
OPERATION
The dosing pump is an electrically operated pump
that receives its operation instructions from the sup-
plemental cabin heater control module. The pump
supplies diesel fuel from the vehicle fuel tank to the
cabin heater.
REMOVAL
NOTE: The dosing pump is serviceable without
removing the supplemental cabin heater from the
vehicle.
(1) Disconnect and isolate the negative battery
cable.
CAUTION: Make sure that the hoist is properly posi-
tioned under the vehicle to prevent damage to the
flexible section of the cabin heater exhaust tube.
(2) Raise and support the vehicle.
(3) Disconnect the wiring harness connector to the
dosing pump by depressing the integral spring and
pulling the connector away from the pump.
NOTE: Utilize an approved fuel storage container to
catch any residual fuel that may drain from the
heater fuel hose or the dosing pump.
(4) Remove the clamp that secures the heater fuel
hose to the dosing pump (Fig. 4).
(5) Disconnect the heater fuel hose from the dosing
pump.
NOTE: Position and retain the heater fuel line to
prevent fuel leakage from the cabin heater unit
while servicing the dosing pump.
(6) Disconnect the fuel line between the dosing
pump and the cabin heater unit.
NOTE: Have an approved fuel storage container
ready to catch any residual fuel that may drain from
the fuel line or the cabin heater unit.(7) Remove the dosing pump from the rubber iso-
lator and the vehicle.
INSTALLATION
(1) Position the dosing pump to the vehicle and
onto the rubber isolator.
(2) Connect the fuel line between the dosing pump
and the cabin heater unit.
NOTE: The connectors should point towards the
cabin heater fuel line.
(3) Connect the heater fuel hose to the dosing
pump.
(4) Install the clamp that secures the heater fuel
hose to the dosing pump. Tighten the clamp securely.
(5) Connect the wire harness connector to the dos-
ing pump by depressing the integral spring and
pushing the connector toward the pump. Verify con-
nector installation.
(6) Lower the vehicle
(7) Reconnect the negative battery cable.
(8) Verify function of the supplemental cabin
heater.
Fig. 4 Dosing Pump Fuel Line
1 - HEATER FUEL LINE
2 - HEATER FUEL HOSE
3 - HEATER AIR INTAKE PIPE
4 - RETAINING CLAMP (2)
5 - DOSING PUMP
RSCABIN HEATER24 - 117
Page 2269 of 2339

FUEL LINE
STANDARD PROCEDURE
CLEANING
(1) Remove the cabin heater fuel line (Refer to 24 -
HEATING & AIR CONDITIONING/CABIN HEAT-
ER/FUEL LINE - REMOVAL).
(2) With the cabin heater fuel line removed from
the vehicle, place a shop cloth on the fuel tank end of
the fuel line to catch any residue, then apply a small
amount of air pressure to the other end of the fuel
line.
(3) Check to see if air pressure is coming from the
tank end of the line. If pressure is flowing unre-
stricted the line is clean.
(4) If the fuel line shows any signs of being
restricted after air pressure is applied, the fuel line
should be replaced.
(5) Install the cabin heater fuel line (Refer to 24 -
HEATING & AIR CONDITIONING/CABIN HEAT-
ER/FUEL LINE - INSTALLATION).
(6) Verify function of the cabin heater.
REMOVAL
CAUTION: Make sure that the hoist is properly posi-
tioned under the vehicle to prevent damage to the
flexible section of the cabin heater exhaust tube.
(1) Raise and support the vehicle.
NOTE: Utilize an approved fuel storage container to
catch any residual fuel that may drain from the
heater fuel hose or the dosing pump.
(2) Remove the two clamps that secure the heater
fuel hose to the dosing pump and the heater fuel line
(Fig. 5).
(3) Disconnect the heater fuel hose from the dosing
pump and the heater fuel line.
(4) Remove the clamp that secures the heater fuel
line to the fuel tank.
(5) Disconnect the heater fuel line from the fuel
tank.
(6) Disconnect the fuel line from the body retain-
ing clips and remove the fuel line from vehicle.
INSTALLATION
WARNING: DO NOT OPERATE THE DIESEL SUP-
PLEMENTAL CABIN HEATER IN AN ENCLOSED
AREA SUCH AS A GARAGE THAT DOES NOT HAVE
EXHAUST VENTILATION FACILITIES. ALWAYS VENT
THE CABIN HEATER EXHAUST WHEN OPERATING
THE CABIN HEATER. ALLOW THE DIESEL SUPPLE-
MENTAL CABIN HEATER TO COOL BEFORE PER-
FORMING ANY SERVICE PROCEDURES TO THE
CABIN HEATER. VERIFY THAT ALL DIESEL SUP-
PLEMENTAL CABIN HEATER FUEL LINES ARE
SECURELY FASTENED TO THEIR RESPECTIVE
COMPONENTS BEFORE PERFORMING ANY SER-
VICE PROCEDURES TO THE CABIN HEATER. FAIL-
URE TO FOLLOW THESE INSTRUCTIONS MAY
RESULT IN PERSONAL INJURY OR DEATH.
(1) Position the cabin heater fuel line to the vehi-
cle and connect the body retaining clips.
(2) Connect the heater fuel line to the fuel tank.
(3) Install the clamp that secure the heater fuel
line to the fuel tank. Tighten the clamp securely.
(4) Connect the heater fuel hose to the dosing
pump and the heater fuel line.
(5) Install the clamps that secure the heater fuel
hose to the dosing pump and the heater fuel line.
Tighten the clamps securely.
(6) Lower the vehicle.
Fig. 5 Dosing Pump Fuel Line
1 - HEATER FUEL LINE
2 - HEATER FUEL HOSE
3 - HEATER AIR INTAKE PIPE
4 - RETAINING CLAMP (2)
5 - DOSING PUMP
24 - 118 CABIN HEATERRS
Page 2270 of 2339

NOTE: Verify that there is more than 1/8 of a tank of
fuel in the vehicle's fuel tank before performing this
procedure. Add fuel, if necessary.
NOTE: Failure to prime the dosing pump after drain-
ing the supplemental cabin fuel line will prevent
cabin heater activation during the first attempt to
start the cabin heater. This will also set a diagnostic
trouble code (DTC) in the cabin heater control's
memory. Do not perform the Dosing Pump Priming
procedure if an attempt was made to start the cabin
heater without priming the dosing pump first. This
will put excess fuel in the cabin heater and cause
smoke to emit from the cabin heater exhaust pipe
when cabin heater activation occurs.
(7) Connect the DRBIIItscan tool to the diagnos-
tic link connector.
(8) Turn the ignition to the ON position.
NOTE: Do not activate the dosing pump prime more
than one time. This will put excess fuel in the sup-
plemental cabin heater and cause smoke to emit
from the cabin heater exhaust pipe when cabin
heater activation occurs.
NOTE: A clicking noise heard coming from the dos-
ing pump indicates that the pump is operational.
(9) With the DRBIIItscan tool in Cabin Heater,
select System Tests and Dosing Pump Prime. Allow
the dosing pump to run for the full 45 second cycle
time. When the 45 second cycle is complete, press
Page Back on the DRBIIItscan tool key pad to exit
the Dosing Pump Prime. The Dosing Pump Priming
procedure is now complete.
HEATER HOSES
REMOVAL
(1) Raise and support the vehicle. Take note of the
location of the flexible section of the cabin heater
exhaust tube.
(2) Drain the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
NOTE: Complete removal of the supplemental cabin
heater from vehicle is not required, lowering the
cabin heater allows easier access to coolant line
clamps.(3) Lower the supplemental cabin heater from the
vehicle (Refer to 24 - HEATING & AIR CONDITION-
ING/CABIN HEATER/HEATER UNIT - REMOVAL).
(4) Remove the clamps from both flexible coolant
line ends.
NOTE: It is recommended that both flexible cabin
heater coolant lines be replaced if either cabin
heater coolant line is damaged.
(5) Remove both coolant lines from vehicle.
INSTALLATION
(1) Install both flexible coolant lines to the supple-
mental cabin heater and install the clamps.
(2) Install the flexible coolant lines to the coolant
pipes and install the clamps.
(3) Install the supplemental cabin heater into the
vehicle (Refer to 24 - HEATING & AIR CONDITION-
ING/CABIN HEATER/HEATER UNIT - INSTALLA-
TION).
(4) Lower the vehicle.
(5) Fill the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(6) Verify operation of the supplemental cabin
heater.
HEATER PIPES
REMOVAL
WARNING: ALLOW THE ENGINE COOLING SYSTEM
TO COOL COMPLETELY BEFORE REMOVING RADI-
ATOR CAP OR DRAINING THE ENGINE COOLING
SYSTEM. PERSONAL INJURY MAY RESULT IF THE
ENGINE COOLING SYSTEM IS OPENED WHILE
ENGINE COOLANT IS HOT AND UNDER PRES-
SURE.
NOTE: Steel heater lines from engine compartment
to the supplemental cabin heater are part of an
assembly that includes the air intake pipe. If the
cabin heater lines or air intake pipe require removal
or replacement the entire cabin heater assembly
will require removal or replacement.
(1) Drain the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(2) Remove clamps from both the EGR cooler and
the lower heater port. Separate hoses from the mat-
ing plumbing port (Fig. 6).
RSCABIN HEATER24 - 119
FUEL LINE (Continued)
Page 2271 of 2339

(3) Remove retaining nut from heater line under
hood bracket.
(4) Raise and support the vehicle. Take note of the
location of the flexible section of the cabin heater
exhaust tube.
(5) Remove the clamps from cabin heater lines to
the rubber connection nearest the tubes. Separate
the hoses from the tube assembly leaving the rubber
hose attached to the cabin heater.
(6) Remove the cabin heater intake pipe from the
heater unit (Refer to 24 - HEATING & AIR CONDI-
TIONING/CABIN HEATER/INLET HOSE -
REMOVAL) (Fig. 7).
(7) Remove heater pipe assembly retaining screws
and remove assembly from vehicle.INSTALLATION
(1) Position the heater pipe assembly and install
the retaining screws.
(2) Install the heater unit intake pipe to the
heater unit (Refer to 24 - HEATING & AIR CONDI-
TIONING/CABIN HEATER/INLET HOSE - INSTAL-
LATION).
(3) Connect heater hoses to the heater unit and
tighten the clamps.
(4) Install heater unit intake pipe to heater unit
(Refer to 24 - HEATING & AIR CONDITIONING/
CABIN HEATER/INLET HOSE - INSTALLATION).
(5) Lower the vehicle.
(6) Install and tighten the retaining nut to the
heater line under the hood bracket.
Fig. 6 Cabin Heater Pipes
1 - HEATER CORE INTAKE PIPE
2 - HEATER CORE RETURN PIPE
3 - A/C LINES
4 - A/C EXPANSION VALVE5 - A/C EXPANSION VALVE GROUND WIRE
6 - CABIN HEATER RETURN PIPE
7 - CABIN HEATER INTAKE PIPE
8 - CABIN HEATER PIPES RETAINING NUT
24 - 120 CABIN HEATERRS
HEATER PIPES (Continued)
Page 2272 of 2339

(7) Connect the heater lines to the heater hoses at
the heater core and EGR port. Position spring clamps
onto the hoses.
(8) Fill the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
HEATER UNIT
REMOVAL
WARNING: DO NOT OPERATE THE DIESEL SUP-
PLEMENTAL CABIN HEATER IN AN ENCLOSED
AREA SUCH AS A GARAGE THAT DOES NOT HAVE
EXHAUST VENTILATION FACILITIES. ALWAYS VENT
THE CABIN HEATER EXHAUST WHEN OPERATING
THE CABIN HEATER. ALLOW THE DIESEL SUPPLE-
MENTAL CABIN HEATER TO COOL BEFORE PER-
FORMING ANY SERVICE PROCEDURES TO THE
CABIN HEATER. VERIFY THAT ALL DIESEL SUP-
PLEMENTAL CABIN HEATER FUEL LINES ARE
SECURELY FASTENED TO THEIR RESPECTIVE
COMPONENTS BEFORE PERFORMING ANY SER-
VICE PROCEDURES TO THE CABIN HEATER. FAIL-
URE TO FOLLOW THESE INSTRUCTION MAY
RESULT IN PERSONAL INJURY OR DEATH.(1) Raise and support the vehicle. Take note of the
location of the flexible section of the cabin heater
exhaust tube.
(2) Drain the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(3) Carefully open one hose to the underbody tube
assembly and drain the remaining coolant. A salvage
hose is a good idea to control the residual coolant, as
flow will occur from both the cabin heater and the
hose and tube assemblies.
(4) Remove the second hose from the underbody
hose and tube assembly.
(5) Loosen the hose and tube assembly from the
toe-board crossmember at two locations.
(6) Disconnect the electrical connector from the
body harness near the toe-board crossmember and
rail.
(7) Remove the wiring harness from the toe-board
crossmember (Refer to 24 - HEATING & AIR CON-
DITIONING/CABIN HEATER/HEATER UNIT -
REMOVAL).
(8) Open the fuel filler cap. Disconnect the rubber
fuel hose between the body tube assembly and the
fuel pump nipple at the body tube joint. A minimal
amount of fuel may flow from the open port.
NOTE: Utilize an approved fuel storage container to
catch any residual fuel.
(9) Loosen the two fasteners at the rail. Take care
to notice that the exhaust tube bracket tab is on top
of the heater bracket and that there are two spacer
washers installed between the rubber grommets.
(10) Remove the flexible section of the cabin
heater exhaust tube from the exhaust tube by loos-
ening the clamp. Remove the hose from the exhaust
tube. Removal of the rail tube assembly may aid in
this service operation (Refer to 24 - HEATING & AIR
CONDITIONING/CABIN HEATER/EXHAUST TUBE
- REMOVAL).
(11) Remove seat hex nut at the heater mounting
flange to crossmember.
(12) Loosen the remaining fasteners which mount
the exhaust tube assembly to the vehicle.
(a) Install a suitable support device under the
cabin heater and secure the cabin heater to the
support.
(13) Loosen the remaining three fasteners to the
crossmembers.
(14) Remove the loosened fasteners that support
the cabin heater while supporting the weight of the
heater.
(15) Swing the cabin heater mounting bracket
from between the exhaust bracket and rail mounting
location. Drain any residual coolant from the cabin
heater.
Fig. 7 Cabin Heater Air Intake And Heater Pipe
Assembly
1 - INTAKE TUBE AIR INTAKE
2 - INTAKE PIPE
3 - RETAINING SCREWS
4 - INTAKE HEATER LINE
5 - RETURN HEATER LINE
RSCABIN HEATER24 - 121
HEATER PIPES (Continued)