Isuzu KB P190. Manual — part 826

Engine Management – V6 – Diagnostics

Page 6C1-2–26

5.4

Cranks But Does Not Run

Definition

The engine cranks normally but does not start.

Checks Actions

Preliminary

•

Perform the preliminary checks. Refer to 4.3

Preliminary Checks in this

Section.

•

Check the immobiliser system for correct operation. Refer to 11A Immobiliser.

Sensor / System

•

Check the engine coolant temperature (ECT) sensor for an incorrect value.
Compare the engine coolant temperature against the intake air temperature (IAT)
on a cold engine. The ECT and IAT sensor values should be within ± 3°C of each
other. Refer to 6C1-3 Engine Management – V6 – Service Operations for details
of the Temperature vs. Resistance Table.

•

Check the mass air flow (MAF) sensor installation. Incorrect installation of the
MAF sensor may cause hard start condition. Refer to 6C1-3 Engine Management
– V6 – Service Operations.

•

Check for a dirty starter motor commutator or brushes that can mask the
crankshaft position sensor signal.

Fuel System

•

Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6.

•

restricted fuel filter,

•

incorrect fuel pressure,

•

contaminated fuel, and

•

incorrect fuel pump relay operation.

•

Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management –
V6 – Service Operations.

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.

N O T E

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.

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.

N O T E

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.

Engine Management – V6 – Diagnostics

Page 6C1-2–28

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.

•

Wiring 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, or

•

motors and generators.

When all diagnosis and repairs are completed, check the system for correct operation.

5.6

Detonation / Spark Knock

Description

The engine produces sharp rapid metallic knocks that are more audible during acceleration.

Checks Actions

Preliminary

Perform the preliminary checks. Refer to 4.3

Preliminary Checks in this Section.

Sensor System

Use Tech 2 to monitor the knock sensor system.

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.

•

Ensure the fuel tank is filled with petrol that has a minimum octane reading of 92.

•

Check for fault conditions that can cause an engine to run lean.

Ignition System

Check the spark plugs for proper heat range. Refer to 6C1-3 Engine Management – V6
– Service Operations.

Engine Mechanical

•

Check the combustion chambers for excessive carbon build-up. Refer to 6A1
Engine Mechanical – V6.

•

Check the camshaft timing. Refer to 6A1 Engine Mechanical – V6.

Additional Checks

•

Check the torque converter clutch (TCC) operation. The TCC applying too soon
can cause the engine to spark knock. Refer to 7C2 Automatic Transmission –
4L60E – Electrical Diagnosis.

When all diagnosis and repairs are completed, check the system for correct operation.

5.7 Dieseling,

Run-on

Description

The engine continues to run after the ignition is switched off but runs very roughly and then stalls.

Engine Management – V6 – Diagnostics

Page 6C1-2–29

Checks Actions

Preliminary

Perform the preliminary checks. Refer to 4.3

Preliminary Checks in this Section.

Fuel System

Inspect the injectors for leaking condition. Refer to 6C1-3 Engine Management – V6 –
Service Operations.

Engine Cooling System

•

Check for engine overheating. Refer to 6B1 Engine Cooling – V6.

•

Check the engine thermostat for proper operation and correct heat range. Refer to
6B1 Engine Cooling – V6.

Engine Mechanical

•

Check for build up of carbon deposit in the combustion chamber, which may
cause hot spots and increased compression ratio. Refer to 6A1 Engine
Mechanical – V6.

•

Using Tech 2, check for incorrect engine idle speed.

Additional

•

If the engine continues to run after the ignition is switched off but the engine runs
normally, check the following:

•

ignition switch operation,

•

voltage feedback from alternator L terminal to ignition switch, and

•

sticking ignition control relay.

When all diagnosis and repairs are completed, check the system for correct operation.

5.8 Hard

Start

Definition

The engine cranks normally but takes longer to start than usual. As soon as the engine runs, the engine may stall
immediately.

Checks Actions

Preliminary

•

Perform the preliminary checks. Refer to 4.3

Preliminary Checks in this

Section.

•

Check the immobiliser system for correct operation. Refer to 11A Immobiliser.

Sensor / System

•

Check the engine coolant temperature (ECT) sensor for an incorrect value.
Compare the engine coolant temperature against the intake air temperature (IAT)
on a cold engine. The ECT and IAT sensor values should be within ± 3°C of each
other. Refer to 6C1-3 Engine Management – V6 – Service Operations for details
of the Temperature vs. Resistance Table.

•

Check the mass air flow (MAF) sensor installation. Incorrect installation of the
MAF sensor may cause hard start condition. Refer to 6C1-3 Engine Management
– V6 – Service Operations.

•

Test the resistance of the crankshaft position (CKP) sensor. The CKP sensor
resistance must be within 700 – 1,200

Ω at all temperatures.

•

Check for dirty starter motor commutator or brushes that can mask the crankshaft
position sensor signal.

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.