2007 ISUZU KB P190 ESP

Engine Cooling – V6 Engine Page 6B1–61

4 Engine Cooling System
Diagnosis
4.1 Poor Heater Operation
Little or no heat coming from the heater, especially at idle could be an indication of a cooling system problem.
As the coolant level begins to get lower than normal, air enters the system to replace the missing coolant. The heater
core is one of the highest parts of the cooling system and therefore, the first area to lose coolant circulation.
At first, with a small amount of coolant loss, lack of heat will be most noticeable at idle. As driving speed increases, the
engine pumps more coolant and more heat is now able to pass through the heater core.
If coolant level drops even lower, heater operation will become less effective, even during normal driving. Cooling and
engine systems can be adversely affected if problem is not corrected before overheating occurs.
4.2 Leaking Cylinder Head Gasket
Combustion gases leaking past the cylinder head gasket can pressurise the cooling system, forcing coolant out of the
system and into the coolant recovery reservoir.
Indications are air bubbles in the coolant or an overflow condition of the recovery reservoir.
4.3 Question the Customer
To avoid needless time and cost in diagnosing cooling system complaints, the customer should be questioned about
driving conditions that place abnormal loads on the cooling system.
1 Is overheating occurring after prolonged idle, in gear, with air conditioning system operating?
If answer is YES – instruct owner on driving techniques that would avoid overheating such as:
• Idle in neutral as much as possible – increase engine rpm to get higher air flow (due to an increase in voltage
to the fan) and coolant flow through the radiator
• Turn air conditioning system off during extended idling periods if overheating is indicated on temperature
gauge. Further diagnostic checks should not be required
2 Is overheating occurring after prolonged driving in slow city traffic, traffic jams, parades, etc?
If answer is YES, explain driving technique to the customer, that would avoid overheating – same as for prolonged idle – No.1. Further diagnostic checks should not be required.
4.4 Diagnostic Chart
If none of the above conditions apply, refer to the following Diagnosis Chart.
To effectively use this chart, question the customer to determine which of the following three categories apply to the
complaint:
1 If complaint is hot indication on temperature gauge.
W as temperature reading accompanied by boiling?
• If answer is YES, go to overheating on diagnosis chart
• If answer is NO, check temperature gauge and sender
2 If complaint is boiling – go to overheating on diagnosis chart.
3 If complaint is coolant loss. Determine if customer is filling the system correctly.
4 If incorrect filling is not the problem, go to coolant loss in the diagnosis chart.

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Engine Management – V6 – General Information Page 6C1-1–12

Battery Voltage Correction Mode
The ECM monitors the battery voltage circuit to ensure the voltage available to the engine management system stays
within the specified range. A low system voltage changes the voltage across the fuel injectors, which affects the fuel
injector flow rate. In addition, a low system voltage fault condition may cause other engine management system
components to malfunction.
The ECM switches to battery voltage correction mode when the ECM detects a low battery voltage fault condition. W hile
in battery voltage correction mode, the ECM performs the following functions to compensate for the low system voltage:
• Increases the injector on-time to maintain the correct amount of fuel being delivered, and
• Increases the idle speed to increase the generator output.
Limp Mode
The programming in the ECM software allows the engine to run in a back-up fuel strategy or limp mode when the ECM
fails to receive signal inputs from critical sensors or when a critical engine management fault condition exists.
The ECM switches to limp mode to enable the vehicle to be driven until service operations can be performed.
Engine Protection Mode
Engine protection mode is engaged to protect engine components from friction damage in the event of an engine over-
temperature condition being detected by the ECM.
W hen the ECM is in engine protection mode, fuel injectors are systematically disabled and re-activated. The injectors
that have been shut down allow the air being drawn into the engine to assist with engine cooling.
Clear Flood Mode
If the engine is flooded with fuel during starting and will not start, the clear flood mode can be manually selected by
depressing the accelerator pedal to wide open throttle (W OT). In this mode, the ECM will completely disable the fuel
injectors, and will maintain this state during engine cranking as long as the ECM detects a W OT condition with engine
speed less than 1,000 rpm.
3.3 Ignition Control System
The electronic ignition system provides a spark to ignite the compressed air / fuel mixture at the correct time. The ECM
maintains correct spark timing and dwell for all engine operating conditions. The ECM calculates the optimum spark
parameters from information received from the various sensors and triggers the appropriate ignition module / coil to fire
the spark plug.
3.4 Starter Motor Operation
The engine control module controls the activation of the start relay in response to inputs from:
• Ignition switch,
• Battery,
• Immobiliser system, and
• Automatic transmission gear selector position / clutch pedal position switch for vehicles with manual transmissions.
3.5 Throttle Actuator Control System
Description
The throttle actuator control (TAC) system is used to improve emissions, fuel economy and driveability. The TAC system
eliminates the mechanical link between the accelerator pedal and the throttle plate and eliminates the need for a cruise
control module and idle air control motor. The TAC system comprises of:

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ISUZU KB P190 2007

Engine Management – V6 – General Information Page 6C1-1–31

4.15 Ignition Coil and Spark Plug
Long-life platinum tip spark plugs are used which, along with
the ignition coil spark plug boot and spring, require
replacement at 100,000 kilometre service intervals. The
spark plugs, featuring a J-gap and a conical seat, do not
require inspection between services, and must not be re-
gapped.
Individual pencil-type ignition coils, one for each cylinder, are
mounted in the centre of the camshaft covers, and have
short boots connecting the coils directly to the spark plugs.
The pencil coil makes use of the space available in the spark
plug cavity in the cylinder head and camshaft cover. As a
pencil coil is always mounted directly on to the spark plug,
no high-tension ignition leads are required, further enhancing
reliability.

Figure 6C1-1 – 38
Pencil coils operate similarly to other compact coils, however
due to their shape, the structure differs considerably.
The central rod core (1) consists of laminations of varying
widths, stacked in packs that are nearly spherical. A yoke
plate (2), made from layered electrical sheet steel, provides
the magnetic circuit. The primary winding (3) is located
around the secondary winding (4), which supports the core.
A printed circuit board, or driver module, (5) is located at the
top of the coil and controls the firing of the coil based on
input from the ECM.
The ECM is responsible for maintaining correct spark timing
and dwell for all driving conditions. The ECM calculates the
optimum spark parameters from information received from
the various sensors, and triggers the appropriate ignition
module which then operates the coil.
The ignition coil / modules are supplied with the following
circuits:
• Ignition feed circuit.
• Ground circuit.
• Ignition control circuit.
• Reference low circuit.

Figure 6C1-1 – 39

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Engine Management – V6 – General Information Page 6C1-1–32

4.16 Intake Air Temperature Sensor
The intake air temperature (IAT) sensor is a thermistor,
which is a resistor that changes it’s resistance value based
on temperature.
The IAT sensor is part of the air mass sensor and is not a
serviceable item. The sensor is a negative temperature
coefficient (NTC) type, intake air 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 IAT and
monitors the return signal which enables it to calculate the
intake air temperature.
The ECM uses this signal to make corrections to the
operating parameters of the system based on changes in air
intake temperature.
Figure 6C1-1 – 40
4.17 Knock Sensor
The knock sensor (KS) signal is used by the ECM to provide
optimum ignition timing while minimising engine knock or
detonation.
The ECM monitors the voltage of the left-hand (Bank 2)
sensor during the 45 degrees after cylinder 2, 4, or 6 has
fired and the voltage of the right-hand (Bank 1) sensor
during the 45 degrees after cylinder 1, 3, or 5 has fired.
If knock occurs in any of the cylinders, the ignition will be
retarded by three degrees for that particular cylinder. If the
knocking then stops, the ignition will be restored to what it
was before in steps of 0.75 degrees.
Should knocking continue in the same cylinder despite of
the ignition being retarded, the ECM will retard the ignition
an additional step of three degrees, and so on, up to a
maximum of 12.75 degrees. The ignition will also be
retarded at high ambient temperatures to counteract
knocking tendencies provoked by high intake air
temperatures.
Should either Bank 1 or Bank 2 sensor fail to work, or
should an open circuit occur, the ignition timing will then be
set at a default strategy that will retard the ignition much
more than normal.
Figure 6C1-1 – 41

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Engine Management – V6 – Diagnostics Page 6C1-2–27

5.5 Cuts Out, Misses
Description
Steady pulsation or jerking that is usually more severe as the engine load increases. This condition is not normally felt
greater than 1500 rpm or 48 km/h. The exhaust has a steady spitting sound at idle or low speed.
Checks Actions
Preliminary • Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this
Section.
• Check the air filter element and intake air ducts for blockages.
• Check for intake manifold vacuum leak.
Sensor / System
• Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters.
The HO2s should respond quickly to different throttle positions.
• Use Tech 2 to monitor the knock sensor system for excessive spark retard
activity. Check for items that cause spark retard activity. Refer to 7.19 DTC
P0327, P0328, P0332 or P0333.
Fuel System • Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6.
• restricted fuel filter,
• incorrect fuel pressure, and
• contaminated fuel.
• Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management –
V6 – Service Operations.
• Perform the fuel injector balance test, refer to 6.3 Fuel Injector Balance
Test in this Section.
• Check for fault conditions that cause an engine to run rich or to run lean.
Ignition System
• Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Check for loose ignition coil grounds.
Engine Mechanical Check for the following engine fault conditions. Refer to 6A1 Engine Mechanical –V6.
• low compression, and
• worn valve train components.

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Engine Management – V6 – Diagnostics Page 6C1-2–30

Checks Actions
Ignition System
• Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Check for loose ignition coil ground circuit.
Engine Mechanical
• Check for excessive oil in combustion chamber. Refer to 6A1 Engine Mechanical
– V6.
• Check for the following engine fault conditions. Refer to 6A1 Engine Mechanical –
V6.
• low compression, and
• worn valve train components.
When all diagnosis and repairs are completed, check the system for correct operation.
5.9 Hesitation, Sag and Stumble
Description
Momentary lack of response or hesitation as the accelerator is depressed. This condition is usually more severe when
first trying to make the vehicle move from a standing start but can occur at any vehicle speed.
Checks Actions
Preliminary • Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this
Section.
• Check the air filter element and intake air ducts for blockages.
Sensor / System
• Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters.
The HO2s should respond quickly to different throttle positions.
• Inspect the accelerator pedal position (APP) sensor harness connector for correct
connection. Poor connection of this connector will not set a DTC.
Fuel System • Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6.
• restricted fuel filter,
• incorrect fuel pressure, and
• contaminated fuel.
• Check the operation of the fuel injectors. Refer to 6C Fuel System – V6.
• Perform the fuel injector balance test, refer to 6.3 Fuel Injector Balance
Test in this Section.
• Check for fault conditions that cause an engine to run rich or to run lean.

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Engine Management – V6 – Diagnostics Page 6C1-2–33

Checks Actions
Sensor / System
• Check the air intake system and crankcase for air leaks.
• Check the PCV System for correct operation. Refer to 6A1 Engine Mechanical –
V6.
• Check for the correct calibration of the speedometer. Refer to 8A Electrical-Body.
• Use Tech 2 to monitor the knock sensor system for excessive spark retard
activity. Check for items that cause spark retard activity.
• Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters.
The HO2s should respond quickly to different throttle positions.
Fuel System • Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6.
− restricted fuel filter,
− incorrect fuel pressure, and
− contaminated fuel.
• Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management –
V6 – Service Operations.
• Perform the fuel injector balance test, refer to 6.3 Fuel Injector Balance
Test in this Section.
• Check the items that cause an engine to run rich.
• Check for foreign material accumulation in the throttle bore, carbon build-up on
the throttle valve or on the throttle shaft.
• Check the throttle body for tampering.
Ignition System
• Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Check for loose ignition coil ground circuit.
Engine Cooling System
• Check the engine thermostat for proper operation and correct heat range. Refer to
6B1 Engine Cooling – V6.
Engine Mechanical Check for the following engine fault conditions. Refer to 6A1 Engine Mechanical – V6.
• low compression, and
• worn valve train components.

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Engine Management – V6 – Diagnostics Page 6C1-2–34

Checks Actions
Additional Checks
• Check the exhaust system for possible restrictions. Refer to 6F Exhaust System –
V6.
• Electromagnetic interference (EMI) on the crankshaft position (CKP) sensor can
cause an engine misfire condition.
Using Tech 2, monitor the engine speed parameter. A sudden increase in the engine speed parameters without moving the throttle position indicates that an
Electromagnetic Interference fault may be present.
W iring harness routing which may be positioned very close to a high voltage or high current device such as the following may induce EMI:
• secondary ignition components, and
• motors and generators.
• Check the torque converter clutch (TCC) operation. A TCC that applies too soon
can cause engine detonation, which will trigger spark retard activity. Refer to 7C2
Automatic Transmission – 4L60E – Electrical Diagnosis.
• Test for other TCM related faults that may cause the transmission to operate in
the default mode. Refer to 7C2 Automatic Transmission – 4L60E – Electrical
Diagnosis.
• Check for transmission mechanical faults such as slipping clutch. Refer to 7C3
Automatic Transmission – 4L60E – Hydraulic and Mechanical Diagnosis.
• Check the brake system including the parking brake for sticking or incorrect
operation.
When all diagnosis and repairs are completed, check the system for correct operation.
5.12 Rough, Unstable, Incorrect Idle or
Stalling
Description
Engine idle speed fluctuates causing the engine to run unevenly. If the engine idle speed drops too low, the engine may
stall.
Checks Actions
Preliminary • Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this
Section.
• Check the air filter element and intake air ducts for blockages.
Sensor / System
• Check the throttle actuator control (TAC) system. Refer to 6C1-3 Engine
Management – V6 – Service Operations.
• Check the air intake system and crankcase for air leaks. Refer to 6C1-3 Engine
Management – V6 – Service Operations.
• Check the PCV System for correct operation. Refer to 6A1 Engine Mechanical –
V6.
• Use Tech 2 to monitor the knock sensor system for excessive spark retard
activity. Check for items that cause spark retard activity.
• Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters.
The HO2s sensor should respond quickly to different throttle positions.

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