Isuzu KB P190. Manual — part 329

6E-282 Engine Control System (4JH1)

Installation Procedure

1. Set the vacuum pressure sensor on the bracket

and tighten a bolt.

2. Connect a harness connector to the vacuum

pressure sensor.

3. Connect the negative battery cable.

Vehicle Speed Sensor (VSS) Replacement

Removal Procedure

M/T & A/T (4WD)

1. Disconnect the negative battery cable.

2. Disconnect a harness connector from the vehicle

speed sensor (VSS).

3. Remove the VSS from the transmission.

A/T (2WD)

1. Disconnect the negative battery cable.

2. Disconnect a harness connector from the vehicle

speed sensor (VSS).

3. Loosen a bolt and remove the VSS from the

transmission.

Installation Procedure

M/T & A/T (4WD)

1. Install the VSS at the transmission.

2. Connect a harness connector to the VSS.

3. Connect the negative battery cable.

M/T & A/T (4WD)

1. Set the VSS at the transmission and tighten a bolt.

2. Connect a harness connector to the VSS.

3. Connect the negative battery cable.

Engine Control System (4JH1) 6E-283

Description And Operation

Engine Control Module (ECM) Description

RTW66ESH001201

The engine control module (ECM) is designed to

withstand normal current draws associated with vehicle

operation. Avoid overloading any circuit. When testing

for opens and shorts, do not ground or apply voltage to

any of the ECM circuits unless instructed to do so. In

some cases, these circuits should only be tested using

a digital multi meter (DMM). The ECM should remain

connected to the ECM harness.

The ECM is located on the floor panel. The ECM mainly

controls the following.

• The fuel system control
• The exhaust gas recirculation (EGR) system

control

• The preheating (glow) system control
• The A/C compressor control
• On-board diagnostics for engine control

The ECM constantly observes the information from

various sensor s. The ECM controls the systems that

affect vehicle performance. The ECM performs the

diagnostic function of the system. The ECM can

recognize operational problems, alert the driver through

the malfunction indicator lamp (MIL), and store

diagnostic trouble codes (DTCs). DTCs identify the

system faults to aid the technician in making repairs.

ECM Voltage Description

The ECM supplies a buffered voltage to various

switches and sensor s. The ECM can do this because

resistance in the ECM is so high in value that a test

lamp may not illuminate when connected to the circuit.

An ordinary shop voltmeter may not give an accurate

reading because the voltmeter input impedance is too

low. Use a 10-megaohm input impedance DMM, to

ensure accurate voltage readings. The input and/or

output devices in the ECM include analog-to-digital

converters, signal buffers, counters, and special drivers.

The ECM controls most components with electronic

switches which complete a ground circuit when turned

ON.

Aftermarket Electrical and Vacuum Equipment

Aftermarket or add-on electrical and vacuum equipment

is defined as any equipment which connects to the

vehicle's electrical or vacuum systems that is installed

on a vehicle after the vehicle leaves the factory. No

allowances have been made in the vehicle design for

this type of equipment. No add-on vacuum equipment

should be added to this vehicle. Add-on electrical

equipment must only be connected to the vehicle's

electrical system at the battery power and ground. Add-

on electrical equipment, even when installed to these

guidelines, may still cause the powertrain system to

malfunction. This may also include equipment not

connected to the vehicle electrical system such as

portable telephones and audios. Therefore, the first

step in diagnosing any powertrain fault is to eliminate all

aftermarket electrical equipment from the vehicle. After

this is done, if the fault still exists, the fault may be

diagnosed in the normal manner.

Electrostatic Discharge Damage

Electronic components used in the ECM are often

designed to carry very low voltage. Electronic

components are susceptible to damage caused by

electrostatic discharge. By comparison, as much as

4,000 volts may be needed for a person to feel even the

zap of a static discharge. There are several ways for a

person to become statically charged. The most

common methods of charging are by friction and

induction.

• An example of charging by friction is a person

sliding across a vehicle seat.

6E-284 Engine Control System (4JH1)

Important:

To prevent possible electrostatic discharge damage,

follow these guidelines:

• Do not touch the ECM connector pins or soldered

components on the ECM circuit board.

• Do not open the replacement part package until

the part is ready to be installed.

• Before removing the part from the package,

ground the package to a known good ground on

the vehicle.

• If the part has been handled while sliding across

the seat, while sitting down from a standing

position, or while walking a distance, touch a

known good ground before installing the part.

• Charge by induction occurs when a person with

well insulated shoes stands near a highly charged

object and momentarily touches ground. Charges

of the same polarity are drained off leaving the

person highly charged with opposite polarity.

Malfunction Indicator Lamp (MIL) Operation

The malfunction indicator lamp (MIL) is located in the

instrument panel cluster (IPC). The MIL will display the

following symbols when commanded ON:

RTW76ESH004001

The MIL indicates that an emission or performance

related fault has occurred and vehicle service is

required. The following is a list of the modes of

operation for the MIL:

• The MIL illuminates for approximately 2 seconds

when the ignition switch is turned ON, with the

engine OFF. This is a bulb test to ensure the MIL

is able to illuminate.

• The MIL remains illuminated after the engine is

started if the ECM detects a fault. A DTC is stored

any time the ECM illuminates the MIL due to an

emission or performance related fault.

Engine Control Component Description

Accelerator Pedal Position (APP) Sensor & Idle

Switch

RTW66ESH001301

The accelerator pedal position (APP) sensor is mounted

on the throttle assembly. The engine control module

(ECM) uses the APP sensor s to determine the amount

of acceleration or deceleration desired by the person

driving the vehicle via the fuel injection control.

The idle switch is also mounted on the intake throttle

assembly. The idle switch is part of the APP sensor

assembly. The idle switch is a normally closed type

switch. When the accelerator pedal is released, the idle

switch signal to the ECM is low voltage.

Engine Control System (4JH1) 6E-285

Crankshaft Position (CKP) Sensor

RTW06ESH000101

RTW66ESH001401

Legend
1. Crankshaft Position (CKP) Sensor

2. Flywheel

3. Slit

The crankshaft position (CKP) sensor is located on top
of the flywheel housing. There are 4 slits spaced 90°

on the flywheel circumference. The CKP sensor is a

magnetic coil type sensor , which generates an AC

signal voltage based on the crankshaft rotational speed.

The ECM monitors both the CKP sensor and injection

pump camshaft position (CMP) sensor signals to

ensure they correlate with each other.

The following waveform aids to diagnose when there is

an oscilloscope or equivalent.

Engine Coolant Temperature (ECT) Sensor

- Amplitudes of CKP sensor signal (CH1) increase

as engine speed increases.

- Each waveform cycle shorten as the engine

speed increases.

Terminal: 90 (CH1), 91 (CH2) (+) / GND (-)
Scale: 10V/div 2ms/div
Condition: Approximately 1000RPM

CH1

0V

CH2

0V

RTW66ESH001501

Legend

1. Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature (ECT) sensor is

installed to the thermostat housing. The ECT sensor is

a variable resistor. The ECT sensor measures the

temperature of the engine coolant. The engine control

module (ECM) supplies 5 volts to the ECT signal circuit

and a ground for the ECT low reference circuit. When

the ECT sensor is cold, the sensor resistance is high.

When the engine coolant temperature increases, the

sensor resistance decreases. With high sensor

resistance, the ECM detects a high voltage on the ECT

signal circuit. With lower sensor resistance, the ECM

detects a lower voltage on the ECT signal circuit.