Isuzu KB P190. Manual - part 827

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. 

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. 

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. 

Engine Management – V6 – Diagnostics 

Page 6C1-2–31 

 

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. 

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 Cooling System 

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

Additional Checks 

• 

Check the generator output voltage. Refer to 6D1-1 Charging System – V6.  

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

5.10  Lack of Power, Sluggishness or 

Sponginess 

Description 

The engine delivers less than normal power. There is little or no increase in vehicle speed when the accelerator pedal is 
partially depressed. 

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 

• 

Use Tech 2 to monitor the knock sensor system for excessive spark retard 
activity. Check for items that cause spark retard activity. 

• 

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 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 can cause the engine to run rich or run lean. 

Engine Management – V6 – Diagnostics 

Page 6C1-2–32 

 

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. 

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 the following engine mechanical fault condition. Refer to 6A1 Engine 
Mechanical – V6. 

• 

low engine compression, and 

• 

worn valve train components. 

Additional Checks 

• 

Check the exhaust system for possible restrictions. Refer to 6F Exhaust System – 
V6. 

• 

Test for other TCM related faults that may cause the transmission to operate in 
the default mode. 

• 

Check for transmission mechanical faults that may produce similar symptoms 
such as slipping clutch. 

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

5.11  Poor Fuel Economy 

Description 

As confirmed by an actual road test, the fuel economy as compared to the previous fuel consumption of the same 
vehicle is noticeably lower. 

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 correct tyre pressure. Refer to the Owners Manual. 

• 

Check the recent driving conditions are the same compared to the previous when 
the fuel consumption is normal. The following are list of driving conditions that 
may affect fuel consumption: 

− 

vehicle load, 

− 

acceleration rate, 

− 

A/C or other electrical equipment use, and 

− 

vehicle used for towing. 

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. 

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 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.