Isuzu KB P190. Service manual — part 816

Engine Management – V6 – General Information

Page 6C1-1–22

4.6

Clutch Pedal Switch Assembly – Manual
Vehicles Only

The cruise control cancel switch (1) is normally closed when
the clutch pedal is at rest, opening when the pedal is
pressed. Activation of this switch removes the signal to the
ECM which will then deactivate the cruise control. For
further information on the cruise control system, refer to
7A1 Clutch – V6.

Figure 6C1-1 – 19

4.7

Engine Control Module

Located at the right front of the engine assembly, the engine
control module (ECM) monitors input signals from the
various sensors and switches connected to the engine
management system. The ECM processes this information,
to control the following:

•

fuel delivery and injection system,

•

throttle actuation system,

•

ignition system,

•

on-board diagnostics,

•

the engine cooling fan, and

•

the air-conditioner compressor clutch (where fitted).

The ECM supplies 5 V to the various sensors through pull-
up resistors to the internal regulated power supplies.

The ECM controls output circuits such as the injectors, etc.
by applying control signal to the ground circuits of the
components through transistors or a device inside the ECM
called a driver. The exception to this is the fuel pump relay
control circuit. The fuel pump relay is the only ECM
controlled circuit where the ECM controls the 12 V sent to
the coil of the relay. The ground side of the fuel pump relay
coil is connected to engine ground.

The ECM communicates directly with the various control
units within the vehicle using the General Motors local area
network (GM LAN) serial data communication protocol.
Refer to 3.9

Serial Data Communication System.

Figure 6C1-1 – 20

Engine Management – V6 – General Information

Page 6C1-1–23

4.8

Engine Coolant Temperature Sensor

The engine coolant temperature (ECT) sensor is a
thermistor, which is a resistor that changes it’s resistance
value based on temperature.

Figure 6C1-1 – 21

The ECT is mounted in the engine coolant stream and as it
is a negative temperature coefficient (NTC) type, low engine
coolant temperature produces a high sensor resistance
while high engine coolant temperature causes low sensor
resistance.

Legend

A Temperature

B Resistance

The ECM provides a 5 V reference signal to the ECT and
monitors the return signal which enables it to calculate the
engine temperature.

The ECM uses this signal to make corrections to the
operating parameters of the system based on changes in
engine coolant temperature.

Figure 6C1-1 – 22

4.9

Electric Cooling Fan

The ECM controls the operation of the electric engine
cooling fan. The ECM applies a pulse width modulated
(PWM) signal to the cooling fan motor to control the fan
speed based on current vehicle conditions. For further
information on cooling fan operation, refer to 6B1 Engine
Cooling – V6.

Figure 6C1-1 – 23

Engine Management – V6 – General Information

Page 6C1-1–24

4.10 Engine Oil Level and Temperature

Sensor

The engine oil level (EOL) and temperature sensor is a dual
purpose sensor and is fitted in the engine sump. It combines
a switch to signal oil level and a thermistor type temperature
sensor to provide oil temperature signal to the ECM.

Figure 6C1-1 – 24

Engine Oil Temperature Sensor

The engine oil temperature sensor is a negative
temperature coefficient (NTC) type. At low engine oil
temperature, the sensor produces a high resistance, whilst
at high temperature the sensor produces a low resistance.

Legend

A Temperature

B Resistance

The ECM provides a 5 V reference signal to the engine oil
temperature sensor and monitors the return signal which
enables it to calculate the engine oil temperature.

Figure 6C1-1 – 25

Engine Management – V6 – General Information

Page 6C1-1–25

Engine Oil Level Sensor

The engine oil level sensor is comprised of a magnetic reed
switch (1) contained within the sensor, a float (2) and a
magnetic pin (3). The magnetic reed switch is a normally
open switch, which closes when a magnet field is present.

When the engine oil level is within specifications, the pin on
the inside of the float is pushed up against the reed switch
(view A). When the oil level drops and the magnetic pin
moves away from the reed switch (view B), the switch
contacts opens.

The ECM provides a 5 V reference signal to the engine oil
temperature sensor and monitors the return signal. The
ECM only monitors the oil level signal prior to engine start-
up, and once the engine is cranking, the ECM disregards
the oil level sensor signal.

Figure 6C1-1 – 26

4.11 Engine Oil Pressure Sensor

The engine oil pressure (EOP) sensor measures engine oil
pressure. When the EOP sensor signal is below a certain
value, the ECM sends a serial data message to the
powertrain interface module (PIM) requesting the PIM to
turn on the engine oil pressure warning lamp.

Figure 6C1-1 – 27