2007 ISUZU KB P190 ignition

Engine Control System (4JH1) 6E-251
Step Action Value(s) Yes No
16 1. Turn OFF the ignition.
2. Keep the 3-amp fused wire with connected.
3. Disconnect the ECM C-56 harness connector.
4. Connect a test lamp between the thermo relay input circuit (pin 33 of C-56 connector) and a
known good ground.
5. Turn ON the ignition, with the engine OFF. DO NOT START the engine.
Does the test lamp illuminate? 

Go to Step 36 Go to Step 24
17 1. Turn OFF the ignition. 2. Keep the 3-amp fused wire with connected.
3. Replace the thermo relay with the horn relay or replace with a known good relay.
4. Connect a 3-amp fused jumper wire between the pressure switch harness (pin 1 of C-24
connector) and a known good ground.
5. Turn ON the ignition, with the engine OFF.
Does the thermo relay click (engage)? 

Go to Step 31 Go to Step 25
18 1. Turn OFF the ignition. 2. Connect the pressure switch harness connector.
3. Remove the grove box in order to access electronic thermostat.
4. Disconnect the electronic thermostat harness connector (C-55).
5. Connect a 3-amp fused jumper wire between the electronic thermostat voltage feed circuit (pin 2 of
C-55 connector) and a known good ground.
6. Turn ON the ignition, with the engine OFF.
Does the thermo relay click (engage)? 

Go to Step 19 Go to Step 26
19 1. Turn OFF the ignition. 2. Connect a test lamp between the electronic thermostat terminal (pin 1 of C-55 connector) and
battery voltage.
3. Turn ON the blower motor switch.
Does the test lamp illuminate? 

Go to Step 20 Go to Step 27
20 1. Turn OFF the ignition. 2. Connect a test lamp between the electronic thermostat voltage feed circuit (pin 3 of C-55
connector) and a known good ground.
3. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate? 

Go to Step 21 Go to Step 28
21 1. Turn OFF the ignition. 2. Connect a test lamp between the electronic thermostat terminal (pin 4 of C-55 connector) and
battery voltage.
3. Turn ON the blower motor switch.
4. Turn ON the A/C switch.
Does the test lamp illuminate? 

Go to Step 33 Go to Step 22

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ISUZU KB P190 2007

6E-252 Engine Control System (4JH1)
Step Action Value(s) Yes No
22 1. Turn OFF the ignition.
2. Remove the center cluster bezel in order to remove HVAC control lever.
3. Disconnect the A/C switch harness connector (B- 57).
4. Connect a test lamp between the A/C switch ground harness (pin 10 of B-57 connector) and
battery voltage.
5. Turn ON the blower motor switch.
Does the test lamp illuminate? 

Go to Step 29 Go to Step 30
23 Repair the open circuit or high resistance on the thermo relay voltage feed circuits between the
thermo relay (pin 2 of X-15 connector) and ECM
(10A) fuse (EB-4), then thermo relay (pin 3 of X-15
connector) and A/C (10A) fuse (EB-13).
Did you complete the repair? 

Go to Step 43 
24 Repair the open circuit or high resistance on thermo
relay input circuit between the ECM (pin 33 of C-56
connector) and the thermo relay (pin 1 of X-15
connector).
Did you complete the repair? 

Go to Step 43 
25 Repair the open circuit or high resistance on the
pressure switch voltage feed circuit between the
thermo relay (pin 5 of X-15 connector) and pressure
switch (pin 1 of C-24) connector.
Did you complete the repair? 

Go to Step 43 
26 1. Test the voltage feed circuit between the
pressure switch (pin 2 of C-24 harness
connector) and electronic thermostat (pin 2 of C-
55 connector) for an open or high resistance.
2. Repair the circuit as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 32
27 1. Test the electronic thermostat switching circuit between the electronic thermostat (pin 1 of C-55
connector) and the blower motor switch (pin 1 of
B-13 connector) for an open or high resistance.
2. Repair the circuit as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 35
28 Repair the open or high resistance on the voltage feed circuit on the electronic thermostat between the
A/C (10A) fuse (EB-13) and the electronic
thermostat (pin 3 of C-55 connector).
Did you complete the repair? 

Go to Step 43 
29 1. Test the electronic thermostat circuit between the
electronic thermostat (pin 4 of C-55 connector)
and A/C switch (pin 11 of B-57 connector) for an
open or high resistance.
2. Repair the circuit as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 34
30 1. Test the A/C switch ground circuit between the A/C switch (pin 10 of B-57 connector) and blower
motor switch (pin 1 of B-13 connector) for an
open or high resistance.
2. Repair the circuit as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 35

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-253
Step Action Value(s) Yes No
31 1. Turn OFF the ignition.
2. Inspect for an intermittent and for poor connections at the thermo relay terminals (pins
1, 2, 3 and 4 of X-15 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 37
32 1. Turn OFF the ignition. 2. Inspect for an intermittent and for poor connections at the harness connector of the
pressure switch (pins 1 and 2 of C-24 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 38
33 1. Turn OFF the ignition. 2. Inspect for an intermittent and for poor connections at the harness connector of the
electronic thermostat (pins 1, 2, 3 and 4 of C-55
connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 39
34 1. Turn OFF the ignition. 2. Inspect for an intermittent and for poor connections at the harness connector of the A/C
switch (pins 10 and 11 of B-57 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 40
35 1. Turn OFF the ignition. 2. Inspect for an intermittent and for a poor connection at the harness connector of the
blower motor switch (pin 1 of B-13 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 41
36 1. Turn OFF the ignition. 2. Inspect for an intermittent and for a poor connection at the harness connector of the ECM
(pin 33 of C-56 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 42
37 Replace the thermo relay. Did you complete the replacement? 

Go to Step 43 
38 Replace the pressure switch. Refer to Heating and
Air Conditioning section.
Did you complete the replacement? 

Go to Step 43 
39 Replace the electronic thermostat. Refer to Heating
and Air Conditioning section.
Did you complete the replacement? 

Go to Step 43 
40 Replace the A/C switch. Refer to Heating and Air
Conditioning section.
Did you complete the replacement? 

Go to Step 43 
41 Replace the blower motor switch. Refer to Heating
and Air Conditioning section.
Did you complete the replacement? 

Go to Step 43 
42 Important: Replacement ECM must be
programmed.
Replace the ECM. Refer to Engine Control Module
(ECM) Replacement in this section.
Did you complete the replacement? 

Go to Step 43 

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ISUZU KB P190 2007

6E-254 Engine Control System (4JH1)
Step Action Value(s) Yes No
43 1. Reconnect all previously disconnected fuse,
relay or harness connector(s).
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Turn ON the blower motor switch.
Does the blower motor turn ON and operate
correctly? 

Go to Char 1 of 2 Step 4 Refer to Applicable
Diagnostic Chart in Heating & Air Conditioning Section



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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-259
Checks Action
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.
• 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 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.
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.
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.

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ISUZU KB P190 2007

6E-260 Engine Control System (4JH1)
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).
• Improper mechanical timing (timing gear)
• Improper valve gap
• Broken or weak valve springs
• W orn camshaft lobes
Electrical System Checks Inspect the engine electrical for the following conditions. Refer to the Engine Electrical
section.
• Inspect the glow plug control (preheating) system operation.
• Inspect for slow cranking speed.
• Inspect for weakened batteries.


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 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 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.

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ISUZU KB P190 2007

6E-266 Engine Control System (4JH1)
Lack of Power, Sluggishness, Sponginess
Checks Action
DEFINITION:The engine delivers less than expected power. There is little or no increase in speed when partially applying the
accelerator pedal.
Preliminary Checks • Diagnostic System Check - Engine Controls.
• Compare the vehicle with a similar unit. Ensure the vehicle has an actual problem.
• Remove the air cleaner and check for dirt, or for air ducts being plugged or
restricted. Replace as necessary.
• Have the tire sizes changed?
• Are excessively heavy loads being carried?
• Inspect for clutch slip.
• Inspect brake drag.
• 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.
• 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 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.
• Use the scan tool to observe the Accelerator Pedal Position Accelerator Pedal
Position. Accelerator Pedal Position parameter should change linearly from 0% to
100% according to the accelerator pedal operation.

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ISUZU KB P190 2007

6E-268 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
• W orn 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 engine overheat condition. Refer to the Engine Cooling section.
• Inspect the A/C operation.
• Inspect the torque converter clutch (TCC) operation (A/T only).


Hesitation, Sag, Stumble
Checks Action
DEFINITION:The vehicle has a momentary lack of response when pushing down on the accelerator. The condition can occur
at any vehicle speed. The condition is usually most severe when trying to make the vehicle move from a stop. If severe
enough, the condition may cause the engine to stall.
Preliminary Checks • Diagnostic System Check - Engine Controls.
• Compare the vehicle with a similar unit. Ensure the vehicle has an actual problem.
• Remove the air cleaner and check for dirt, or for air ducts being plugged or
restricted. Replace as necessary.
• Inspect for a proper transmission shift pattern and down shift operation.
• Inspect the fuel quality (cetane index).
• Inspect the engine oil level and quality.
• Inspect the scan tool Data List in this section.
• 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 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 parameter should change linearly from 0% to
100% according to the accelerator pedal operation.

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ISUZU KB P190 2007