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15-38
Relay box
A/C
compressorHFM (intake air
temperature)Cooling fan
module
MB 5 A/T (ATF
temperature)Coolant
temperature
sensor
(12) Cooling fan control
A. Overview of cooling fan and A/C compressor
The cooling system maintains the engine temperature at an efficient level during all engine operating
conditions. The water pump draws the coolant from the radiator. The coolant then circulates through
water jackets in the engine block, the intake manifold, and the cylinder head. When the coolant
reaches the operating temperature of the thermostat, the thermostat opens. The coolant then goes
back to the radiator where it cools. The heat from automatic transmission is also cooled down through
the radiator by circulating the oil through the oil pump. ECU controls the electric cooling fans with three
cooling fan relays to improve the engine torque and air conditioning performance.
For detailed information, refer to Chapter "Air Conditioning System".
B. Components
D20DTR ECU
Refrigerant
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15-490000-00
E. Cautions
Use only specified Engine Oil (approved by MB Sheet 229.51) for CDPF. -
Use only specified engine oil (Low Ash Oil) ▶
The vehicle equipped with CDPF should use specific engine oil to improve the engine
performance and fuel economy, and ensure the service life of CDPF. -
Issue with normal engine oil ▶
Sulfur, one of the contents of engine oil is burned and generates soot that is not regenerated by
the DPF. This remains on the filter as ashes and keeps accumulating. Eventually, this ashes will
block the filter. -
Benefit for specified engine oil ▶
Minimized the sulfur content of engine oil which reduces the service life.
Improved fuel economy and emission level of CO2 with high performance and low viscosity.
Increased service life of engine oil with high resistance to temperature. -
-
-
Problems when using unspecified engine oil ▶
The service life of filter may be reduced by 30% or more by the ashes accumulated on the filter.
The fuel economy may be reduced because of engine rolling resistance, frequent regeneration of
DPF. -
-
These problems are also caused by oil with high sulfur content, such as tax exemption oil and
heating oil, etc. *
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01-70000-00
2. DESCRIPTION AND OPERATION
1) Cleanliness and Care
An automobile engine is a combination of many machined, honed, polished and lapped surfaces with
tolerances that are measured in the ten-thousandths of an inch. When any internal engine parts are
serviced, care and cleanliness are important. A liberal coating of engine oil should be applied to friction
areas during assembly, to protect and lubricate the surfaces on initial operation.
Proper cleaning and protection of machined surfaces and friction areas is part of the repair procedure.
This is considered standard shop practice even if not specifically stated.
Whenever valve train components are removed for service, they should be kept in order.
They should be installed in the same locations, and with the same mating surfaces, as when they were
removed. Battery cables should be disconnected before any major work is performed on the engine.
Failure to disconnect cables may result in damage to wire harness or other electrical parts.
2) On-Engine Service
Disconnect the negative battery cable before removing or installing any electrical unit, or when a
tool or equipment could easily come in contact with exposed electrical terminals.
Disconnecting this cable will help prevent personal injury and damage to the vehicle.
The ignition must also be in LOCK unless otherwise noted.
Notice Any time the air cleaner is removed, the intake opening -
Any time the air cleaner is removed, the intake opening should be covered. This will protect
against accidental entrance of foreign material, which could follow the intake passage into the
cylinder and cause extensive damage when the engine is started. -
Page 398 of 796

07-6
1. GENERAL DESCRIPTION
The cooling system maintains the engine temperature at an efficient level during all engine operating
conditions. When the engine is cold, the cooling system cools the engine slowly or not at all. This slo
w
cooling of the engine allows the engine to warm up quickly. The cooling system includes a radiator and
recovery subsystem, cooling fans, a thermostat and housing, a water pump, and a water pump drive
belt. The timing belt drives the water pump. All components must function properly for the cooling
system to operation. The water pump draws the coolant from the radiator.
The coolant then circulates through water jackets in the engine block, the intake manifold, and the
cylinder head. When the coolant reaches the operating temperature of the thermostat, the thermostat
opens. The coolant then goes back to the radiator where it cools. This system directs some coolant
through the hoses to the heat core. This provides for heating and defrosting. The coolant reservoir is
connected to the radiator to recover the coolant displaced by expansion from the high temperatures.
The coolant reservoir maintains the correct coolant level. The cooling system for this vehicle has no
radiator cap or filler neck. The coolant is added to the cooling system through the coolant reservoir.
Page 417 of 796
01-4
Make sure a connector is connected
securely. Loose connection results in
malfunction. -
When inspecting the airbag system, make
sure to use a diagnostic device, not a circuit
tester.When disconnecting a connector equipped with
a lock, press it down to the direction in the below
figure. -
When checking voltage or continuity of the
connector terminal with a circuit tester,
connect the tester probe to the terminal at the
harness side. For a sealed type connector,
connect the probe to the terminal through the
hole in the rubber cap of the wiring. Take
care not to damage the insulation of the
wires. Insert the probe until it contacts the
terminal completely. -
Page 449 of 796
02-18
This function does not work if the vehicle speed is over 3 km/h.
The system outputs “UNLOCK” for 5 seconds (T2) from 0.5 seconds after the driver’s door
is opened and the door lock switch is changed to “LOCK” (while the ignition key is in ignition
switch).
The system outputs “UNLOCK” for 5 seconds (T2) when the door lock switch is changed to
“LOCK” from “UNLOCK” and the driver’s door is closed within 0.5 seconds (T1) (while the
ignition key is in ignition switch). 1.
2.
3. ▶Key Reminder
Operating conditions for (*1) and (*2) -
(*1): Driver’s door is opened and driver’s door lock switch is turned to LOCK
(*2): Passenger’s door is opened and passenger’s door lock switch is turned to LOCK
Page 450 of 796

02-198710-01
▶All Door Lock Prevention Function when a Door is Opened
When a door is opened, all doors should be unlocked for 5 seconds if inputs LOCK signal. 1.
The LOCK signal means the central door locking (REKES, central door lock switch, knob switch)
except LOCK input by rear door knob.
After unlocking and opening only the driver’s door with remote control key under armed
mode (driver’s door is unlocked but passenger’s and rear doors are locked), only the
driver’s door generates unlock signal when trying to lock the driver’s door with the driver’s
door opened.
Above operations is regardless of key positions and have priority over the ignition key reminder
function. -
-
-
When the door is closed during unlock output for 5 seconds under item 1 condition, the unlock
output stops. 2.
All doors except tailgate and hood output “UNLOCK” for 5 seconds (T1) when the “LOCK”
signal is inputted (while the ignition key is removed and a of door is opened).
When the door is closed during unlock output for 5 seconds, the unlock output stops. -
-
Page 451 of 796
02-20
3) Mark Lamp Left on Warning
The chime buzzer in the ICM box sounds with the interval of 0.8 second when opening the
driver’s door while the tail lamp is turned on and the ignition key is removed.
The buzzer output stops when turning off the tail lamp and closing the driver’s door.
The system outputs “UNLOCK” for 5 seconds when the driver’s and passenger’s door lock
switch is locked (while the tail lamp is turned on and the driver’s door is opened).
This function is not available when the ignition key is in “ON” position. 1.
2.
3.
4.