2007 ISUZU KB P190 engine coolant

6E-176 Engine Control System (4JH1)
DTC P0645 (Symptom Code 4) (Flash Code 46)
Circuit Description
The engine control module (ECM) controls the ai
r
conditioning (A/C) compressor relay, which supplies
power to the A/C compressor clutch based on A/C
request input to the ECM from the heating, ventilation
and air conditioning (HVAC) controls. The ECM
commands the A/C compressor relay ON at engine run.
If the ECM detects an open circuit or short to ground on
the A/C compressor relay control circuit, this DTC will
set.
Condition for Running the DTC
• The ignition switch is ON.

• The A/C compressor relay is once commanded
ON.
Condition for Setting the DTC
• The ECM detects a low voltage condition on the
A/C compressor relay control circuit for longer than
3 seconds when the relay is commanded OFF.
Action Taken When the DTC Sets
• The ECM illuminates the malfunction indicato
r
lamp (MIL) when the diagnostic runs and fails.
Condition for Clearing the MIL/DTC
• The ECM turns OFF the MIL when the diagnostic
runs and does not fail.
• A history DTC clears after 40 consecutive driving
cycles without a fault. Or clear with the scan tool.
Diagnostic Aids
• If an intermittent condition is suspected, refer to
Intermittent Conditions in this section.
Notice:
• The A/C compressor relay is commanded OFF
when the engine coolant temperature is reached
around 105°C (221°F) and it commanded ON
again below 100°C (212°F).

DTC P0645 (Symptom Code 4) (Flash Code 46)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views


Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check-
Engine Controls? 
Go to Step 2 Go to Diagnostic
System Check-
Engine Controls
2 1. Install the scan tool. 2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Turn ON the blower motor switch and the A/C compressor switch.
5. Turn OFF the A/C compressor switch.
6. Monitor the Diagnostic Trouble Code (DTC) Information with the scan tool.
Does the DTC fail this ignition? 

Go to Step 3 Go to Diagnostic
Aids
3 1. Turn OFF the ignition. 2. Replace the A/C compressor relay with the tail relay or replace with a known good relay.
3. Turn ON the ignition, with the engine OFF.
4. Turn ON the blower motor switch and the A/C compressor switch.
5. Turn OFF the A/C compressor switch.
6. Monitor the DTC Information with the scan tool.
Does the DTC fail this ignition? 

Go to Step 4 Go to Step 14
4 1. Turn OFF the ignition. 2. Inspect the ECM (10A) fuse (EB-4) in the engine room fuse block.
Is the ECM (10A) fuse (EB-4) open? 

Go to Step 5 Go to Step 6
5 Replace the ECM (10A) fuse (EB-4). If the fuse continues to open, repair the short to ground on one
of the circuits that is fed by the ECM (10A) fuse (EB-
4) or replace the shorted attached component fed by
the ECM (10A) fuse (EB-4).
Did you complete the repair? 

Go to Step 16 

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-179
DTC P0645 (Symptom Code 8) (Flash Code 46)
Circuit Description
The engine control module (ECM) controls the ai
r
conditioning (A/C) compressor relay, which supplies
power to the A/C compressor clutch based on A/C
request input to the ECM from the heating, ventilation
and air conditioning (HVAC) controls. The ECM
commands the A/C compressor relay ON at engine run.
If the ECM detects a short to battery or ignition voltage
on the A/C compressor relay control circuit, this DTC
will set.
Condition for Running the DTC
• The ignition switch is ON.

• The A/C compressor relay is once commanded
ON.
Condition for Setting the DTC • The ECM detects a high voltage condition on the
A/C compressor relay control circuit for longer than
3 seconds when the relay is commanded ON.
Action Taken When the DTC Sets • The ECM illuminates the malfunction indicato
r
lamp (MIL) when the diagnostic runs and fails.
Condition for Clearing the MIL/DTC
• The ECM turns OFF the MIL when the diagnostic
runs and does not fail.
• A history DTC clears after 40 consecutive driving
cycles without a fault. Or clear with the scan tool.
Diagnostic Aids • If an intermittent condition is suspected, refer to
Intermittent Conditions in this section.
Notice: • The A/C compressor relay is commanded OFF
when the engine coolant temperature is reached
around 105°C (221°F) and it commanded ON
again below 100°C (212°F).

DTC P0645 (Symptom Code 8) (Flash Code 46)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check-
Engine Controls? 
Go to Step 2 Go to Diagnostic
System Check-
Engine Controls
2 1. Install the scan tool. 2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Turn ON the blower motor switch and the A/C compressor switch.
5. Monitor the Diagnostic Trouble Code (DTC) Information with the scan tool when the A/C
Relay Command parameter is ON.
Does the DTC fail this ignition? 

Go to Step 3 Go to Diagnostic
Aids
3 1. Turn OFF the ignition. 2. Replace the A/C compressor relay with the tail relay or replace with a known good relay.
3. Start the engine.
4. Turn ON the blower motor switch and the A/C compressor switch.
5. Monitor the DTC Information with the scan tool when the A/C Relay Command parameter is ON.
Does the DTC fail this ignition? 

Go to Step 4 Go to Step 5
4 1. Test the control circuit of the A/C compressor relay between the ECM (pin 41 of C-56
connector) and the A/C compressor relay (pin 5
of X-14 connector) for a short to battery or
ignition voltage.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition? 

Go to Step 7 Go to Step 6
5 Replace the A/C compressor relay. Did you complete the replacement? 

Go to Step 7 

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ISUZU KB P190 2007

6E-204 Engine Control System (4JH1)
DTC P1173 (Symptom Code 3) (Flash Code 22)
Circuit Description
The engine coolant temperature (ECT) sensor is
installed to the thermostat housing. The ECT sensor is
a variable resistor. The ECT sensor has a signal circuit
and a low reference circuit. The ECT sensor measures
the temperature of the engine coolant. The engine
control module (ECM) supplies 5 volts to the ECT signal
circuit and a ground for the ECT low reference circuit.
W hen the ECT sensor is cold, the sensor resistance is
high. W hen the engine coolant temperature increases,
the sensor resistance decreases. W ith high senso
r
resistance, the ECM detects a high voltage on the ECT
signal circuit. W ith lower sensor resistance, the ECM
detects a lower voltage on the ECT signal circuit. If the
ECM detects an excessive high coolant temperature,
this DTC will set.
Condition for Running the DTC
• The ignition switch is ON.
Condition for Setting the DTC • The ECM detects an excessive high coolant
temperature for longer than 30 seconds.
Action Taken When the DTC Sets • The ECM does not illuminate the malfunction
indicator lamp (MIL) when the diagnostic runs and
fails.
Condition for Clearing the DTC
• A history DTC clears after 40 consecutive driving
cycles without a fault. Or clear with the scan tool.
Diagnostic Aids
• If an intermittent condition is suspected, refer to
Intermittent Conditions in this section.
•
After starting the engine, the ECT should rise
steadily to about 80°C – 85°C (176°F – 185°F)
then stabilize when the thermostat opens.
• Use the Temperature vs. Resistance table to test
the ECT sensor at various temperature levels to
evaluate the possibility of a skewed sensor.
A
skewed sensor could result in poor driveabilit
y
concerns.
Notice: • This DTC is caused by an engine overheat
condition (i.e. low engine coolant level). Since this
DTC does not illuminate any lamps, clear the DTC
and ensure there are no signs of engine damage.
Excessive engine overheat may damage internal
engine components.

DTC P1173 (Symptom Code 3) (Flash Code 22)

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check-
Engine Controls? 
Go to Step 2 Go to Diagnostic
System Check-
Engine Controls
2 1. Install the scan tool. 2. Turn OFF the ignition for 30 seconds.
3. Start the engine and wait until engine is fully warms upped.
4. Observe the Engine Coolant Temperature (ECT) parameter with the scan tool.
Is the ECT parameter more than the specified
value? 100°C (212°F)
Go to Step 4 Go to Step 3
3 Ask the driver if overheat is caused by low engine coolant level, etc.
If engine overheat has experienced, the engine must
be inspected and repaired as necessary.
Did you complete the action? 

Go to Step 6 
4 1. Test the ECT sensor at various temperature
levels to evaluate the possibility if a skewed
sensor.
2. Replace the ECT sensor as necessary.
Did you find and correct the condition? 

Go to Step 6 Go to Step 5

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Engine Control System (4JH1) 6E-205
Step Action Value(s) Yes No
5 1. Test the engine cooling system for the following
condition. Refer to diagnosis of the engine
cooling system section for testing. • Engine coolant level
• Engine coolant leakage
• Cooling fan belt slippage
• Cooling fan clutch working
• Thermostat working
• W ater pump working
• Radiator clogging
2. Repair or replace as necessary.
Did you find and correct the condition? 

Go to Step 6 Go to Diagnostic
Aids
6 1. Reconnect all previously disconnected harness connector(s).
2. Clear the DTCs with the scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine and wait until engine is fully warms upped.
5. Observe the ECT parameter with the scan tool.
Is the ECT parameter more than the specified
value? 100°C (212°F)
Go to Step 4 Go to Step 7
7 Observe the DTC Information with the scan tool. Are there any DTCs that you have not diagnosed?  Go to Diagnostic
Trouble Code (DTC) List System OK


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Engine Control System (4JH1) 6E-239
Glow Control System Check
Description
The glow control system consists of the engine control
module (ECM), the glow relay and glow plugs. The glo
w
control system is operated when the engine coolant
temperature is low, which allows easier engine starting.
The ECM commands the glow relay ON for a certain
length of time at ignition switch is ON with engine OFF.
In after glow phase, the glow plugs remain energized fo
r
a certain period with engine run.


Glow Control Operation
•
The pre glow control system operates when the
engine coolant temperature is less than 30 °C
(86 °F).
• The after glow control system operates when the
engine coolant temperature is less than 60 °C
(140 °F).

Glow Control System Check
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check-
Engine Controls? 
Go to Step 2 Go to Diagnostic
System Check-
Engine Controls
2 1. Install the scan tool. 2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Monitor the Diagnostic Trouble Code (DTC) Information of the engine control system with the
scan tool and check whether following DTC(s) is
set: • P0115 (Symptom Code 1 & 2)
• P0380 (Symptom Code 4 & 8)
• P0381 (Symptom Code 4 & 8)
Are any of the above DTC(s) set? 

Refer to Applicable DTC Go to Step 3
3 1. Turn OFF the ignition.
2. Make sure the metal bus bar that connects switched battery voltage supply terminal (E-49)
and all glow plugs is secured tightly.
3. Turn ON the ignition, with the engine OFF
4. Connect a test lamp between the metal bus bar (glow plug power supply E-49 terminal) and a
known good ground.
5. Perform the Glow Relay test with the scan tool.
6. Command the Glow Relay ON with the scan tool while observing the test lamp.
Does the test lamp turn ON only when commanded
ON with the scan tool? 

Go to Step 4 Go to Step 5
4 1. Turn OFF the ignition. 2. Remove the metal bus bar from the glow plugs.
3. Measure resistance of each glow plug between the glow plug terminals and a known good
ground. Make sure to record all measurements
and take them quickly as to not allow engine
temperature changes between measurements.
Are the resistances within the specified value each
other? 1
Ω
System OK Go to Step 15

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ISUZU KB P190 2007

6E-242 Engine Control System (4JH1)
DTC A/C Compressor System Check
Description
W hen air conditioning (A/C) and blower fan are
selected, and if the system has a sufficient refrigerant
charge. A 12-volt signal is supplied to the A/C request
input of the Engine Control Module (ECM). The A/C
request signal may be temporarily canceled during
system operation by the electronic thermostat in the
evaporator to prevent the evaporator icing. Also, it is
cancelled when the pressure switch detected abnormal
pressure in the line. W hen the A/C request signal is
received by the ECM, the ECM supplies a ground from
the A/C compressor relay if the engine operating
conditions are within acceptable ranges. W ith the A/C
compressor relay energized, voltage is supplied to the
compressor clutch coil. The ECM will enable the
compressor clutch to engage whenever A/C has been
selected with the engine running and enable conditions
are met.
Condition for Running the A/C Compressor:
• The engine is running.
• The A/C switch is ON.
• The engine coolant temperature (ECT) is less than
105 °C(221 °F).

A/C Compressor System Check
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Chart 1 of 2
Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check-
Engine Controls? 
Go to Step 2 Go to Diagnostic
System Check – Engine Controls
2 1. Install the scan tool. 2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Monitor the Diagnostic Trouble Code (DTC) Information of the engine control system with the
scan tool and check whether following DTC(s) is
set: • P0115 (Symptom Code 1 & 2)
• P0645 (Symptom Code 4 & 8)
Are any of the above DTC(s) set? 

Refer to Applicable DTC Go to Step 3
3 1. Turn ON the ignition, with the engine OFF.
2. Turn ON the blower motor switch.
Does the blower motor turn ON and operate
correctly? 

Go to Step 4 Refer to Applicable
Diagnostic Chart in Heating & Air Conditioning Section
4 1. Turn OFF the blower motor switch. 2. Keep the A/C switch OFF.
Does the A/C Request Signal parameter indicate
OFF? 

Go to Step 5 Go to Chart 2 of 2
with heater Step 1 OR
Go to Chart 2 of 2
without heater Step 1
5 1. Start the engine and let the engine idle. 2. Keep the blower motor switch OFF.
3. Keep the A/C switch OFF.
Does the A/C compressor clutch keep OFF
(disengage)? 

Go to Step 6 Go to Step 11
6 1. Turn ON the blower motor switch. 2. Keep the A/C switch OFF.
Does the A/C compressor clutch keep OFF
(disengage)? 

Go to Step 7 Go to Chart 2 of 2
with heater Step 7 OR
Go to Chart 2 of 2
without heater Step 4

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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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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