Isuzu KB P190. Manual - part 324

6E-262  Engine Control System (4JH1) 

Checks Action 

Additional Checks 

• Electromagnetic interference (EMI) on the reference circuit can cause an engine miss 

condition. The scan tool can usually detect EMI by monitoring the engine speed. A 
sudden increase in speed with little change in actual engine speed change indicates that 
EMI is present. If a problem exists, check routing of high voltage components, such as 
fuel injection solenoid valve wiring, near the sensor circuits. 

• Inspect for faulty engine mounts. 
• Inspect faulty crank pulley. 
• Inspect faulty generator & A/C compressor. 
• 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. 

 
 

Cut Out, Misses 

Checks Action 

DEFINITION:A constant jerking that follows the engine speed, usually more pronounced as the engine load increase. The 
exhaust has a steady spitting sound at idle, low speed, or hard acceleration for the fuel starvation that can cause the engine to 
cut-out. 
Preliminary Check 

• Diagnostic System Check - Engine Controls. 
• Inspect that the harness connectors are correctly connected. 
• 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 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 observe the Accelerator Pedal Position. Accelerator Pedal 

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

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

is not damaged. 

Engine Control System (4JH1)  6E-263 

Checks Action 

Fuel System Checks 

Inspect the fuel system for the following conditions. Refer to the Fuel System section. 
• Inspect for water contamination in the fuel.  
• Inspect for external fuel leaks or fuel leakage into the engine oil.  
• Inspect the fuel lines between the fuel tank and fuel injection pump for tightness and 

all fuel hoses for cuts, cracks and for the use of proper clamps.  

Notice:  The fuel system from the fuel tank(s) to the fuel injection pump is under a 
slight vacuum with the engine running. As a result, air can enter the fuel system if 
these connections are not tight. Air in the fuel system will cause fuel injection pump 
internal pressure fluctuations especially at high engine speed and load. 
• Inspect for air in the fuel system.  
Notice: If many air bubbles appear in the fuel, check the fuel system line connections 
between the fuel tank and the fuel injection pump for tightness and all fuel hoses for 
cuts, cracks and for the use of proper clamps. 
a. Remove the fuel hose that connects to the fuel injection pump suction side. 
b. Substitute a clear hose. 
Notice: A hose must be cleaned. 
c. Connect the clear hose to the fuel injection pump. 
d. Bleed the fuel system. 
e. Let the engine run at idle for at least 2 minutes. 
f. Accelerator the engine between idle and W.O.T. (accelerator pedal full travel) many 

times while observing the clear hose. 

• Inspect the fuel tank vent hose for a plugged or kinked.  
• Inspect inside the fuel tank for any foreign material that may be getting drawn into 

the fuel line pickup causing a blocked condition. Draw fuel from the fuel tank at the 
fuel line (as close to the fuel tank as possible) going to the fuel pickup tube to verify a 
clean stream of fuel comes out (use the hand-held vacuum pump 5-8840-0279-0/J-
23738-A with a clear hose or equivalent). This will ensure the fuel pickup tube is not 
cracked drawing air into the fuel line. 

• Inspect the fuel injection pump operation. 
Notice: The fuel injection pump must be timed to the engine. 
Inspect the eye bolt for any type of restriction or collapsed gauze filter. 
Notice: If any type of restriction found, check for a condition that causes contaminated 
fuel, such as the customer is using an aftermarket fuel filter or extended maintenance 
interval. Also inspect fuel waxing or icing that is caused by an incorrect fuel type used 
in winter season or water intrusion in the fuel system. 

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 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 mass air flow (MAF) sensor. 

Additional Checks 

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

volts. 

• Electromagnetic interference (EMI) on the reference circuit can cause an engine 

miss condition. The scan tool can usually detect EMI by monitoring the engine 
speed. A sudden increase in speed with little change in actual engine speed change 
indicates that EMI is present. If a problem exists, check routing of high voltage 
components, such as fuel injection solenoid wiring, near the sensor circuits. 

 
 

Surges/Chuggles 

Checks Action 

DIFINITION:The engine has a power variation under a steady throttle or cruise. The vehicle seems to speed up and slow down 
with no change in the accelerator pedal. 

6E-264  Engine Control System (4JH1) 

Checks Action 

Preliminary Checks 

• Diagnostic System Check - Engine Controls. 
• Ensure the driver understands the torque converter clutch (TCC) operation. 
• Ensure the driver understands the A/C compressor operation. 
• Use the scan tool in order to make sure the Vehicle Speed parameter reading 

matches the vehicle speedometer. 

• Inspect the engine control module (ECM) and fuel injection pump control unit (PCU) 

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

• Inspect that the harness connectors are correctly connected. 
• Inspect the fuel type and quality. 
• 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 Mass Air Flow (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 parameter should change linearly from 0% to 100% according to the 
accelerator pedal operation. Also inspect the Accelerator Pedal Position indicating 
angle when the accelerator pedal is steady. If the indicating angle fluctuates, check 
for an intermittent open, high resistance in the circuits or for a skewed sensor. 

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

is not damaged. 

Engine Control System (4JH1)  6E-265 

Checks Action 

Fuel System Checks 

Inspect the fuel system for the following conditions. Refer to the Fuel System section. 
• Inspect for water contamination in the fuel.  
• Inspect for external fuel leaks or fuel leakage into the engine oil.  
• Inspect the fuel lines between the fuel tank and fuel injection pump for tightness and 

all fuel hoses for cuts, cracks and for the use of proper clamps.  

Notice:  The fuel system from the fuel tank(s) to the fuel injection pump is under a 
slight vacuum with the engine running. As a result, air can enter the fuel system if 
these connections are not tight. Air in the fuel system will cause fuel injection pump 
internal pressure fluctuations especially at high engine speed and load. 
• Inspect for air in the fuel system.  
Notice: If many air bubbles appear in the fuel, check the fuel system line connections 
between the fuel tank and the fuel injection pump for tightness and all fuel hoses for 
cuts, cracks and for the use of proper clamps. 
a. Remove the fuel hose that connects to the fuel injection pump suction side. 
b. Substitute a clear hose. 
Notice: A hose must be cleaned. 
c. Connect the clear hose to the fuel injection pump. 
d. Bleed the fuel system. 
e. Let the engine run at idle for at least 2 minutes. 
f. Accelerator the engine between idle and W.O.T. (accelerator pedal full travel) many 

times while observing the clear hose. 

• Inspect the fuel tank vent hose for a plugged or kinked.  
• Inspect inside the fuel tank for any foreign material that may be getting drawn into 

the fuel line pickup causing a blocked condition. Draw fuel from the fuel tank at the 
fuel line (as close to the fuel tank as possible) going to the fuel pickup tube to verify a 
clean stream of fuel comes out (use the hand-held vacuum pump 5-8840-0279-0/J-
23738-A with a clear hose or equivalent). This will ensure the fuel pickup tube is not 
cracked drawing air into the fuel line.  

• Inspect the fuel injection pump operation.  
Notice: The fuel injection pump must be timed to the engine. 
• Inspect the eye bolt for any type of restriction or collapsed gauze filter.  
Notice: If any type of restriction found, check for a condition that causes contaminated 
fuel, such as the customer is using an aftermarket fuel filter or extended maintenance 
interval. Also inspect fuel waxing or icing that is caused by an incorrect fuel type used 
in winter season or water intrusion in the fuel system. 
• 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. 

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 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. 

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. (A/T only)