Isuzu KB P190. Manual - part 487

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-331

Air Intake System Checks

Inspect the air intake system for the following conditions.

• Air cleaner, air intake ducts and charge air cooler for a restriction, holes, or leaks.

• A restriction in the turbocharger inlet duct.

• Intake throttle valve for a stuck condition.

• A restriction or leak in the intake manifold.

Exhaust System Checks

Inspect the exhaust system for a possible restriction. Refer to the Exhaust System
section.

Engine Mechanical Checks

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

• Poor cylinder compression.

• Improper mechanical timing (timing gear and timing chain).

• Improper valve gap.

• Broken or weak valve springs.

• Worn camshaft lobes.

• Incorrect basic engine parts such as camshaft, cylinder head, pistons, etc..

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 injector solenoid valve wiring, near the sensor circuits.

• Faulty engine mounts.

• Faulty crank pulley.

• Faulty generator & A/C compressor.

• Generator output voltage.

• EGR system operating correctly. Refer to EGR Control System Check in this

section.

• A/C operation.

Checks

Action

6E-332   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

High Idle Speed

Checks

Action

Definition:
Engine idle speed is higher than normal in regardless of engine coolant temperature.

Preliminary Checks

• Diagnostic System Check - Engine Controls.

• Inspect that the harness connectors are correctly connected.

• Use the scan tool to compare the engine speed and tachometer on the instrument

panel (IP) cluster.

• Inspect the battery voltage. If the battery voltage is less than 11 volts, the ECM set

the idle speed 50RPM higher than normal.

• Inspect the A/C operation.

• Inspect the fuel type and quality.

• Inspect the engine oil level.

• Inspect the Scan Tool Data List in this section.

• Inspect the Service Bulletin.

Sensor Checks

Inspect the engine control sensors for the following conditions. Refer to the Scan Tool
Data List in this section.

• Compare the Coolant Temperature with the Intake Air Temperature (IAT) and Fuel

Temperature (FT) parameters 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 in each circuit or for a skewed sensor.

Notice: The mass air flow (MAF) sensor is heated and as a result the IAT may indicate
a higher than normal intake air temperature if the ignition switch is being ON.

• Observe the Fuel Rail Pressure (FRP) Sensor parameter with the engine OFF. The

FRP Sensor should read 0.9 to 1.0 volt with the key ON and engine OFF after the
engine has stopped running for a minimum of 1 minute. If not, check for high
resistance in each circuit or for a skewed sensor.

• Observe the Fuel Rail Pressure parameter at idle in Neutral. The Fuel Rail Pressure

should always be within 27 to 33 MPa (3,900 to 4,800 psi) after warm up.

• Observe the Accelerator Pedal Position (APP). APP 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.

• Fuel injectors. Remove the injectors and visually inspect. (Injector tip(s) may be

damaged)

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-333

Cuts Out

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

• Inspect the Scan Tool Data List in this section.

• Inspect the Service Bulletin.

Sensor Checks

Inspect the engine control sensors for the following conditions. Refer to the Scan Tool
Data List in this section.

• Observe the Mass Air Flow (MAF) parameter for a skewed or slow MAF sensor.

• Observe the Fuel Rail Pressure (FRP) Sensor parameter with the engine OFF. The

FRP Sensor should read 0.9 to 1.0 volt with the key ON and engine OFF after the
engine has stopped running for a minimum of 1 minute. If not, check for high
resistance in each circuit or for a skewed sensor.

• Observe the Fuel Rail Pressure and Desired Fuel Rail Pressure parameter between

idle and W.O.T. (accelerator pedal full travel) in Neutral. Fuel Rail Pressure
parameter should follow within 

± 5 MPa (± 725 psi) quick enough.

• Observe the Accelerator Pedal Position (APP). APP parameter should change

linearly from 0 to 100% according to the accelerator pedal operation.

• Crankshaft position (CKP) sensor is tight and the sensor rotor is not damaged.

Fuel System Checks

Inspect the fuel system for the following conditions. Refer to Fuel System Check Chart
and appropriate procedure in the Fuel System section.

• Air in the fuel system.

• Water contamination in the fuel.

• Fuel waxing or icing.

• Fuel filter indicator lamp is continuously or frequently turned ON with engine run.

• In-tank fuel pump operation. Refer to In-tank Fuel Pump System Check in this

section.

• Fuel leak off from the fuel pressure limiter valve and fuel injectors.

• Fuel lines between the fuel tank and fuel supply pump for being crushed, kinked,

tightness, cracks and plugged.

• Inside the fuel tank for any foreign material that may be getting drawn into the fuel

line pickup causing a blocked condition.

• Perform the Cylinder Balance Test with a scan tool.

• Perform the Injector Force Drive with a scan tool.

• Observe the Fuel Compensation for each cylinder at idle on the scan tool.

Air Intake System Checks

Inspect the air intake system for the following conditions.

• Air cleaner, air intake ducts and charge air cooler for a restriction, holes, or leaks.

• A restriction in the turbocharger inlet duct.

• Intake throttle valve for a stuck condition.

• A restriction or leak in the intake manifold.

• A restriction or damaged at MAF sensor.

Exhaust System Checks

Inspect the exhaust system for a possible restriction. Refer to the Exhaust System
section.

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 injector solenoid valve wiring, near the sensor circuits.

6E-334   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

Surges

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.

Preliminary Checks

• Diagnostic System Check - Engine Controls.

• 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 ECM 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 programmed fuel injector ID code for each cylinder.

• Inspect the Scan Tool Data List in this section.

• Inspect the Service Bulletin.

Sensor Checks

Inspect the engine control sensors for the following conditions. Refer to the Scan Tool
Data List in this section.

• Observe the Mass Air Flow (MAF) parameter for a skewed or slow MAF sensor.

• Observe the Fuel Rail Pressure (FRP) Sensor parameter with the engine OFF. The

FRP Sensor should read 0.9 to 1.0 volt with the key ON and engine OFF after the
engine has stopped running for a minimum of 1 minute. If not, check for high
resistance in each circuit or for a skewed sensor.

• Observe the Fuel Rail Pressure and Desired Fuel Rail Pressure parameter between

idle and W.O.T. (accelerator pedal full travel) in Neutral. Fuel Rail Pressure
parameter should follow within 

± 5 MPa (± 725 psi) quick enough.

• Observe the Accelerator Pedal Position (APP). APP 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 Fuel System Check chart
and appropriate procedure in the Fuel System section.

• Air in the fuel system.

• Water contamination in the fuel.

• Fuel waxing or icing.

• Fuel filter indicator lamp is continuously or frequently turned ON with engine run.

• In-tank fuel pump operation. Refer to In-tank Fuel Pump System Check in this

section.

• Fuel leak off from the fuel pressure limiter valve and fuel injectors.

• Fuel lines between the fuel tank and fuel supply pump for being crushed, kinked,

tightness, cracks and plugged.

• A plugged fuel tank vent valve and hose.

• Inside the fuel tank for any foreign material that may be getting drawn into the fuel

line pickup causing a blocked condition.

• Fuel supply pump operation.

Notice: The fuel supply pump must be timed to the engine and adjustment value must
be learned to the ECM.

• Perform the Cylinder Balance Test with a scan tool.

• Perform the Injector Force Drive with a scan tool.