Isuzu KB P190. Manual - part 326

6E-270  Engine Control System (4JH1) 

Checks Action 

Engine Mechanical Check  

Inspect the engine mechanical for the following conditions. Refer to the Engine 
Mechanical section.  
• Inspect for poor cylinder compression. Proper compression is more than 2100 kPa 

(309 psi). 

• Improper mechanical timing  
• Improper valve gap 
• Broken or weak valve springs 
• Worn camshaft lobes 

Additional Checks 

• Inspect the generator output voltage. Repair if less than 9 volts or more than 16 

volts. 

• Inspect the EGR system operating correctly. 
• Inspect the A/C operation. 
• Inspect the torque converter clutch (TCC) operation. 

 
 

Fuel Knock/Combustion Noise 

Checks Action 

DEFINITION:A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change 
with the throttle opening. 
Preliminary Checks 

• Diagnostic System Check - Engine Controls. 
• Ensure the vehicle has an actual problem. 
• Inspect for smoke associated with the combustion noise. 
• Inspect the fuel quality (cetane index). 
• Inspect the scan tool Data List in this section. 
• Inspect the Service Bulletins for ECM software updates. 

Sensor Checks 

Inspect the engine control sensors for the following conditions. Refer to the scan tool 
Data List in this section. 
• Use the scan tool to compare the Engine Coolant Temperature (ECT) with the Intake 

Air Temperature (IAT) and Fuel Temperature (FT) on a cold engine condition. If the 
difference among temperature reading is more than 5°C (9°F) on a cold engine, 
check for high resistance on the low reference circuit and signal circuit or for a 
skewed sensor.  

Notice: The mass air flow (MAF) sensor is heated and as a result the IAT sensor may 
indicate a higher than normal intake air temperature if the ignition switch is being ON. 
FT sensor is internal to the PCU and it is part of the fuel injection pump assembly. 
• Use the scan tool to compare the MAF Sensor parameter with the Desired MAF 

parameter. Start the engine and warm up (allow engine coolant temperature to reach 
at least 60°C [140°F]). The MAF Sensor parameter must follow the Desired MAF 
parameter within 100 mg/strk. If not, inspect the air intake system, EGR system 
components and contaminated, skewed or slow MAF sensor.  

• Inspect the crankshaft position (CKP) sensor is tight and the flywheel circumference 

is not damaged. 

Fuel System Checks 

• If excessive smoke is present, check for an injection nozzle(s).Remove each glow 

plug from the cylinder head and inspect the tip of the glow plugs for wet by fuel. Use 
the cylinder compression gauge. Proper compression is more than 2100 kPa (309 
psi). If poor compression is observed, inspect the engine mechanical.  

• Inspect the fuel injection nozzle(s) for proper splay condition or operating pressure.  
Notice: Only first stage of operating pressure can be checked. 
• Inspect the timing device operating correctly. Observe the Actual Injection Timing 

parameter with the scan tool while running the engine. The Actual Injection Timing 
parameter must follow the Desired Injection Timing within 2°CA on each engine 
speed. Engine idle > around 2000 RPM> around 3000 RPM. If not, inspect the fuel 
system restriction, air in the fuel or fuel injection pump operation. 

Engine Control System (4JH1)  6E-271 

Checks Action 

Engine Mechanical Checks 

Inspect the engine mechanical for the following conditions. Refer to the Engine 
Mechanical section. 
• Inspect for poor cylinder compression. Proper compression is more than 2100 kPa 

(309 psi). 

• Inspect for incorrect basic engine parts such as camshaft, cylinder head, pistons, 

etc. 

• Inspect for any excessive oil entering combustion chamber. 

Additional Checks 

• Inspect the EGR system operating correctly. 
• Inspect other possible causes that can make similar noise such as loose component 

parts, bracket, mount and weak clutch damper spring. 

 
 

Poor Fuel Economy 

Checks Action 

DEFINITION:Fuel economy, as measured by actual road tests and several tanks of fuel, is noticeably lower than expected. 
Also, the economy is noticeably lower than it was on this vehicle at one time, as previously shown by actual road tests. 
Preliminary Checks 

• Remove the air cleaner and check for dirt, or for air ducts being plugged or 

restricted. Replace as necessary. 

• Inspect the driving habits of the owner. 
• Is the A/C ON full time, defroster mode ON? 
• Are the tires at the correct pressure? 
• Are the tire sizes changed?  
• Are excessively heavy loads being carried? 
• Is the acceleration too much, too often? 
• Inspect for clutch slip. 
• Inspect brake drag. 
• Inspect dive belt tension. 
• Inspect for a proper transmission shift pattern and down shift operation (A/T only). 
• Inspect the fuel quality (cetane index). 
• Inspect the engine oil level and quality. 
• Suggest to the owner to fill the fuel tank and recheck the fuel economy. 
• Suggest to the driver to read the Important Facts on Fuel Economy in the Owner 

Manual. 

• Inspect the odometer is correctly operated. 
• Inspect the Service Bulletins for ECM software updates. 

Sensor Checks 

Inspect the engine control sensors for the following conditions. Refer to the scan tool 
Data List in this section.  
• Use the scan tool to compare the Engine Coolant Temperature (ECT) with the Intake 

Air Temperature (IAT) and Fuel Temperature (FT) on a cold engine condition. If the 
difference among temperature reading is more than 5°C (9°F) on a cold engine, 
check for high resistance on the low reference circuit and signal circuit or for a 
skewed sensor.  

Notice: The mass air flow (MAF) sensor is heated and as a result the IAT sensor may 
indicate a higher than normal intake air temperature if the ignition switch is being ON. 
FT sensor is internal to the PCU and it is part of the fuel injection pump assembly. 

Fuel System Checks 

Inspect the fuel system for the following conditions. Refer to the Fuel System section.  
• Inspect the fuel type and quality.  
• Check fuel leak. 

Cooling System Checks 

Inspect the cooling system for the following conditions. Refer to the Cooling System 
Section.  
• Inspect the engine coolant level. 
• Inspect the engine thermostat for always being open or for the wrong heat range. 
• Inspect the engine cooling fan for always being ON. 

6E-272  Engine Control System (4JH1) 

Checks Action 

Air Intake System Checks  

Inspect the air intake system for the following conditions.  
• Inspect the air cleaner and air intake ducts for a restriction, holes, or leaks. 
• Inspect for a restriction or leak in the intercooler. 
• Inspect for a restriction in the turbocharger inlet duct. 
• Inspect for a restriction or deposit in the intake throttle bore. 
• Inspect for a restriction or leak in the intake manifold. 
• Inspect for a restriction or damage at MAF sensor. 

Exhaust System Checks 

Inspect the exhaust system for a possible restriction. Refer to the Exhaust System 
section.  
• Inspect for a restriction in the catalytic converter or exhaust pipes. 

Engine Mechanical Checks 

Inspect the engine mechanical for the following conditions. Refer to the Engine 

Mechanical section. 

• Inspect for poor cylinder compression. Proper compression is more than 2100 kPa 

(309 psi). 

 
 

Excessive Smoke (Black Smoke) 

Checks Action 

DEFINITION:Black smoke under load, idle or start up hot or cold. 

Preliminary Check 

• Ensure the vehicle has an actual problem. 
• Inspect the engine control module (ECM) and fuel injection pump control unit (PCU) 

grounds for being clean, tight, and in their proper locations. 

• Remove the air cleaner and check for dirt, or for air ducts being plugged or 

restricted. Replace as necessary. 

• Inspect the fuel quality (cetane index). 
• Inspect the engine oil level and quality. 
• Inspect the Service Bulletins for ECM software updates. 

Sensor Checks  

Inspect the engine control sensors for the following conditions. Refer to the scan tool 
Data List in this section. 
• Use the scan tool to compare the Engine Coolant Temperature (ECT) with the Intake 

Air Temperature (IAT) and Fuel Temperature (FT) on a cold engine condition. If the 
difference among temperature reading is more than 5°C (9°F) on a cold engine, 
check for high resistance on the low reference circuit and signal circuit or for a 
skewed sensor.  

Notice: The mass air flow (MAF) sensor is heated and as a result the IAT sensor may 
indicate a higher than normal intake air temperature if the ignition switch is being ON. 
FT sensor is internal to the PCU and it is part of the fuel injection pump assembly. 
• Use the scan tool to compare the MAF Sensor parameter with the Desired MAF 

parameter. Start the engine and warm up (allow engine coolant temperature to reach 
at least 60°C [140°F]). The MAF Sensor parameter must follow the Desired MAF 
parameter within 100 mg/strk. If not, inspect the air intake system, EGR system 
components and contaminated, skewed or slow MAF sensor. 

• Use the scan tool to observe the Accelerator Pedal Position Accelerator Pedal 

Position. Accelerator Pedal Position indicating angle parameter should change 
linearly from 0% to 100% according to the accelerator pedal operation. 

Fuel System Checks 

Inspect the fuel system for the following conditions. Refer to the Fuel System section. 
• Inspect the fuel injection nozzle(s) for proper splay condition or operating pressure.  
Notice: Only first stage of operating pressure can be checked. 
• Inspect the timing device operating correctly. Observe the Actual Injection Timing 

parameter with the scan tool while running the engine. The Actual Injection Timing 
parameter must follow the Desired Injection Timing within 2°CA on each engine 
speed. Engine idle > around 2000 RPM> around 3000 RPM. If not, inspect the fuel 
system restriction, air in the fuel or fuel injection pump operation. 

Engine Control System (4JH1)  6E-273 

Checks Action 

Air Intake System Checks 

Inspect the air intake system for the following conditions.  
• Inspect the air cleaner and air intake ducts for a restriction, holes, or leaks. 
• Inspect for a restriction or leak in the intercooler. 
• Inspect for a restriction in the turbocharger inlet duct. 
• Inspect for a restriction or deposit in the intake throttle bore. 
• Inspect for a restriction or leak in the intake manifold. 
• Inspect for a restriction or damage at MAF sensor. 
• Inspect for a worn or damaged turbocharger turbine wheel, shaft or compressor 

wheel. Refer to turbocharger inspection in the Engine Mechanical section. 

Exhaust System Checks 

Inspect the exhaust system for a possible restriction. Refer to the Exhaust System 
section.  
• Inspect for a restriction in the catalytic converter or exhaust pipes. 

Engine Mechanical Check  

Inspect the engine mechanical for the following conditions. Refer to the Engine 
Mechanical section.  
• Inspect for poor cylinder compression. Proper compression is more than 2100 kPa 

(309 psi). 

• Inspect for incorrect basic engine parts such as camshaft, cylinder head, pistons, 

etc. 

• Inspect for any excessive oil entering combustion chamber. 
• Improper mechanical timing  
• Improper valve gap 
• Broken or weak valve springs 
• Worn camshaft lobes 

Additional Checks 

• Inspect the EGR system operating correctly. 
• Inspect the excessive blow-by gasses. 
• Inspect the scan tool Data List in this section. 

 
 

Excessive Smoke (White Smoke) 

Checks Action 

DIFINITION:White smoke under load, idle or start up hot or cold. 

Preliminary Check 

• Ensure the vehicle has an actual problem. 
• Inspect the engine control module (ECM) and fuel injection pump control unit (PCU) 

grounds for being clean, tight, and in their proper locations. 

• Inspect the fuel quality (cetane index). 
• Inspect the Service Bulletins for ECM software updates. 

Sensor Check 

Inspect the engine control sensors for the following conditions. Refer to the scan tool 
Data List in this section. 
• Use the scan tool to compare the Engine Coolant Temperature (ECT) with the Intake 

Air Temperature (IAT) and Fuel Temperature (FT) on a cold engine condition. If the 
difference among temperature reading is more than 5°C (9°F) on a cold engine, 
check for high resistance on the low reference circuit and signal circuit or for a 
skewed sensor.  

Notice: The mass air flow (MAF) sensor is heated and as a result the IAT sensor may 
indicate a higher than normal intake air temperature if the ignition switch is being ON. 
FT sensor is internal to the PCU and it is part of the fuel injection pump assembly. 
• Inspect the crankshaft position (CKP) sensor is tight and the flywheel circumference 

is not damaged. 

Fuel System Checks 

Inspect the fuel system for the following conditions. Refer to the Fuel System section. 
• Inspect the fuel injection nozzle(s) for proper splay condition or operating pressure. 
Notice: Only first stage of operating pressure can be checked. 
• Inspect the timing device operating correctly. Observe the Actual Injection Timing 

parameter with the scan tool while running the engine. The Actual Injection Timing 
parameter must follow the Desired Injection Timing within 2°CA on each engine 
speed. Engine idle > around 2000 RPM> around 3000 RPM. If not, inspect the fuel 
system restriction, air in the fuel or fuel injection pump operation.