DESCRIPTION AND OPERATION
Page 51
THERMOSTAT
This is a piston-type thermostat with piston, bulb,
seal and housing in a single assembly. It has
lower pressure drop compared to earlier types.
The thermostat is mounted on the front of the
cylinder head.
ENGINE COOLING FAN
The cooling fan (Figure 40) runs via a viscous
drive through which fan speed is electronically
controlled by the EECU. In earlier designs, fan
speed was controlled by a temperature sensing
bi-metal unit. A bi-metal thermostat gauges only
the air passing over it. With precise EECU
control, fan speed is continuously adjusted in
response to several interrelated influences. This
makes for efficient cooling with low fuel
consumption.
40
Figure 40 — Engine Cooling Fan
Other fan drive options include On/Off Fan
Clutches and Electronically Modulated Fan
Drives. Refer to Engine Cooling Service Manual,
7-002, for a complete description of all available
fan drive systems.
Engine Management System
ENGINE ELECTRONIC CONTROL UNIT
(EECU)
41
Figure 41 — EECU and Cooler
The Engine Electronic Control Unit (EECU) is
located on the left side of the engine just below
the inlet manifold. The EECU is cooled by fuel
circulating through a plate attached to the cover
of the unit. The fuel comes from the tank on its
way to the pump.
Algorithms, called maps, are programmed in the
EECU so that it can translate sensor data into
action. These maps enable the EECU to receive
status information from the sensors and send
functional data to the actuators so they can
simultaneously assume the proper posture for the
safest, most efficient operation of the engine in
any given instant.
Due to the EECU self-learning capability, it is
necessary to reset learned EECU parameters
after servicing some engine-related components.
This allows the EECU to learn the new
component's behavior. After servicing is
complete, perform the “Learned Data Reset”
located in VCADS.
1. Solenoid Valve and
Speed Sensor
2. Connector (to EECU)
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