Isuzu KB P190. Manual - part 486

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-327

Scan Tool Snapshot

The scan tool can be set up to take a Snapshot of the parameters available via serial
data. The Snapshot function records live data over a period of time. The recorded data
can be played back and analyzed. The scan tool can also graph parameters singly or in
combinations of parameters for comparison. The Snapshot can be triggered manually
at the time the symptom is noticed, or set up in advance to trigger when a DTC sets.
An abnormal value captured in the recorded data may point to a system or component
that needs to be investigated further.
Refer to the scan tool Users Guide for more information.

DRM Memory

Use data stored in the DRM memory or use manual trigger function. The DRM has
ability to store engine log data when an event of DTC. The manual trigger function is to
store the log data by an arbitrary operation of the driver when an event of wrong vehicle
performance that is instead of an event of DTC. If the driver presses and releases the
manual trigger switch once, that time becomes a trigger and one log data before and
behind the trigger is stored in the DRM memory.
Refer to the DRM Users Guide for more information.

Checks

Action

6E-328   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

Hard Start

Checks

Action

Definition:
The engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but immediately dies.

Preliminary Checks

• Diagnostic System Check - Engine Controls.

• Ensure the driver is using the correct starting procedure.

• 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.

• 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.

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

• Camshaft position (CMP) sensor is tight and the timing chain sprocket 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.

• External fuel leaks or high engine oil level.

• 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.

• Observe the FRP Regulator Feedback current on the scan tool.

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-329

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.

Electrical System Checks

Inspect the engine electrical for the following conditions. Refer to the Engine Electrical
section.

• Glow plug control system operation. Refer to Glow Control System Check in this

section.

• Slow cranking speed.

• Weakened batteries.

Checks

Action

6E-330   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

Rough, Unstable, or Incorrect Idle and Stalling

Checks

Action

Definition:
Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition 
may be severe enough to stall the engine.

Preliminary Checks

• Diagnostic System Check - Engine Controls.

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

restricted. Replace as necessary.

• 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.

• 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.

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

• Camshaft position (CMP) sensor is tight and the timing chain sprocket 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.

• External fuel leaks or high engine oil level.

• 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.

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

• Observe the FRP Regulator Feedback current on the scan tool.