2007 ISUZU KB P190 check engine

Engine Control System (4JH1) 6E-245
Step Action Value(s) Yes No
2 1. Turn OFF the ignition.
2. Remove the thermo relay from the engine room relay block.
3. Turn ON the ignition, with the engine OFF.
Does the A/C Request Signal parameter indicate
OFF? 

Go to Step 3 Go to Step 4
3 1. Turn OFF the ignition. 2. Reinstall the thermo relay.
3. Remove the radiator grille in order to access the pressure switch.
4. Disconnect the pressure switch harness connector (C-24).
5. Turn OFF the blower motor switch.
6. Turn OFF the A/C switch.
7. Turn ON the ignition, with the engine OFF.
Does the A/C Request Signal parameter indicate
OFF? 

Go to Step 6 Go to Step 5
4 Repair the short to battery or ignition voltage on the thermo relay signal input circuit between the thermo
relay (pin 1 of X-15 connector) and the engine
control module (ECM) (pin 33 of C-56 connector).
Did you complete the repair? 

Go to Step 39 
5 Repair the short to ground 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 39 
6 Repair the short to ground between the pressure
switch (pin 2 of C-24 connector) and the electronic
thermostat (pin 2 of C-55 connector), then electronic
thermostat (pin 1 of C-56 connector) and the A/C
switch (pin 5 of B-57 connector).
Did you complete the repair? 

Go to Step 39 
7 1. Test the A/C switch circuits shorted each other.
(pins 1 and 5 of B-57 connector).
2. Repair the circuits as necessary.
Did you find and correct the condition? 

Go to Step 39 Go to Step 36
8 1. Test the circuit between the blower motor switch (pin 1 of B-13 connector) and the A/C switch (pin
1 of B-57 connector) for a short to ground.
2. Repair the circuits as necessary.
Did you find and correct the condition? 

Go to Step 39 Go to Step 37
9 Inspect the A/C (10A) fuse (EB-13) in the engine room fuse block.
Is the A/C (10A) fuse (EB-13) open? 

Go to Step 10 Go to Step 11
10 1. Replace the A/C (10A) fuse (EB-13). If the fuse continues to open, repair the short to ground on
a circuit fed by the fuse or check for a shorted
attached component.
2. Repair the short to ground or replace the component as necessary.
Did you complete the repair? 

Go to Step 39 

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ISUZU KB P190 2007

6E-250 Engine Control System (4JH1)
Step Action Value(s) Yes No
7 Repair the short to ground between the pressure
switch (pin 2 of C-24 connector) and the electronic
thermostat (pin 2 of C-55 connector).
Did you complete the repair? 

Go to Step 43 
8 1. Test the electronic thermostat switching circuits
shorted each other. (pins 1 and 2 of C-55
connector).
2. Repair the circuits as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 39
9 1. Test the electronic thermostat circuit between the electronic thermostat (pin 4 of C-55 connector)
and the A/C switch (pin 11 of B-57 connector) for
a short to ground.
2. Repair the circuits as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 40
10 1. Test the ground circuit among the electronic thermostat (pin 1 of C-55 connector), the blower
motor switch (pin 1 of B-13 connector) and the
A/C switch (pin 10 of B-57 connector) for a short
to ground.
2. Repair the circuits as necessary.
Did you find and correct the condition? 

Go to Step 43 Go to Step 41
11 Inspect the A/C (10A) fuse (EB-13) in the engine room fuse block.
Is the A/C (10A) fuse (EB-13) open? 

Go to Step 12 Go to Step 13
12 1. Replace the A/C (10A) fuse (EB-13). If the fuse continues to open, repair the short to ground on
a circuit fed by the fuse or check for a shorted
attached component.
2. Repair the short to ground or replace the component as necessary.
Did you complete the repair? 

Go to Step 43 
13 1. Turn OFF the ignition.
2. Remove the thermo relay from the engine room relay block.
3. Connect a test lamp between the voltage feed circuit (pins 2 and 3 of X-15 connector) and a
known good ground.
4. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate on both circuits? 

Go to Step 14 Go to Step 23
14 1. Turn OFF the ignition. 2. Reinstall the thermo relay.
3. Remove the radiator grille in order to access the pressure switch.
4. Disconnect the pressure switch harness connector (C-24).
5. Connect a 3-amp fused jumper wire between the pressure switch harness (pin 1 of C-24
connector) and a known good ground.
6. Turn ON the ignition, with the engine OFF.
Does the thermo relay click (engage)? 

Go to Step 15 Go to Step 17
15 Does the A/C Clutch Switch parameter indicate ON? 
Go to Step 18 Go to Step 16

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-255
Symptoms – Engine Controls
Symptoms – Engine Controls
Important Preliminary Inspections Before Starting
Perform Diagnostic System Check – Engine Controls
before using the symptom tables, and verify that all o
f
the following are true:
• The engine control module (ECM) and malfunction
indicator lamp (MIL) are operating correctly.
• There are no diagnostic trouble codes (DTCs)
stored, or a DTC exists but without the MIL.
• The scan tool data is within the normal operating
range. Refer to scan tool Data List in this section.
• Verify the customer concern and locate the correct
symptom in the table of contents. Inspect the items
indicated under that symptom.
Visual and Physical Inspection
Several of the symptom procedures ask for careful
visual and physical inspection. This step is extremel
y
important. The visual and physical inspection can lead
to correcting a problem without further inspections, and
can save valuable time. Ensure that:
• The ECM grounds are clean, tight, and in thei
r
proper location.
• The vacuum hoses are not split or kinked, and
properly connected. Inspect thoroughly for an
y
type of leak or restriction.
• The mass air flow (MAF) sensor is properl
y
installed. The arrows on the plastic portion of the
sensor must point toward the engine.
• The air intake ducts are not collapsed or damaged.
• There are no leaks at the MAF sensor, an
y
connections or intake manifold sealing surfaces.
• The engine harness wiring and terminals are
properly connected and are not pinched or cut.
Intermittent
Important:
Inspect for improper installation of electrical
components if an intermittent condition exists. Inspect
for aftermarket add-on electrical equipment devices,
lights, and cellular phones. Verify that no aftermarket
equipment is connected to the keyword 2000 serial data
circuit. If you cannot locate an intermittent condition, a
cellular phone communication signal may cause the
condition.
Important:
The problem may or may not turn ON the MIL or store a
DTC.

Faulty electrical connections or wiring cause most
intermittent problems. Perform a careful visual and
physical inspection of the suspect connectors for the
following conditions:
• Improperly mated connector halves
• Terminals that are not seated
• Terminals that are damaged or improperly formed
Reform or replace connector terminals in the problem
circuit in order to ensure proper contact tension.
Remove the terminal from the connector body in orde
r
to inspect for poor terminal wire connection.
Road test the vehicle with the DMM connected to the
suspected circuit. An abnormal reading that occurs
when the malfunction occurs is a good indication that
there is a malfunction in the circuit being monitored.
Use the scan tool in order to help detect intermittent
conditions. Useful features of the scan tool include the
following:
• Trigger the Snapshot feature in order to capture
and store engine parameters when the malfunction
occurs. Review this stored information in order to
see the specific running conditions that caused the
malfunction.
• Use the Plot Function on the scan tool in order to
plot selected data parameters. Review this stored
information to aid in locating an intermittent
problem. Refer to the scan tool Users Guide fo
r
more information.
Important:
If the intermittent condition exists as a start and then
stall, test for DTCs relating to the vehicle theft deterrent
system. Test for improper installation of electrical
options such as lights, cellular phones, etc.
Any of the following may cause an intermittent MIL with
no stored DTC:
• The ECM grounds are loose or dirty. Refer to
Engine Controls Schematics.
• The MIL circuit intermittently shorted to ground.
• Electrical system interference caused by a
malfunctioning relay, ECM driven solenoid, o
r
switch. The electrical component can cause a
sharp electrical surge. Normally, the problem will
occur when the malfunctioning component is
operating.
• There is an open diode across the A/C
compressor clutch or any other open diodes.



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6E-256 Engine Control System (4JH1)
Important:
The following symptom tables contain groups o
f
possible causes for each symptom. The order of these
procedures is not important. If the scan tool readings do
not indicate the problems, then proceed in a logical
order, easiest to check or most likely to cause first. In
order to determine if a specific vehicle is using a
particular system or component, refer to Engine
Controls Schematics for an application.
Use the following tables when diagnosing a symptom
complaint:
• Intermittent Conditions
• Hard Start
• Rough, Unstable, or Incorrect Idle and Stalling
• Cuts Out, Misses
• Surge/Chuggles
• Lack of Power, Sluggishness, or Sponginess
• Hesitation, Sag, Stumble
• Fuel Knock/Combustion Noise
• Poor Fuel Economy
• Excessive Smoke (Black Smoke)
• Excessive Smoke (W hite Smoke)



Intermittent Conditions
Checks Action
DEFINITION:The problem is not currently present but is indicated in DTC History.
OR
There is a customer complaint, but the symptom cannot currently be duplicated, if the problem is not DTC related.
Preliminary Checks • Refer to Symptoms – Engine Controls before starting.
Harness/Connector Many intermittent open or shorted circuits are affected by harness/connector
movement that is caused by vibration, engine torque, bumps/rough pavement, etc.
Test for this type of condition by performing the applicable procedure from the
following list:
• Move related connectors and wiring while monitoring the appropriate scan tool data.
• Move related connectors and wiring with the component commanded ON, and OFF,
with the scan tool. Observe the component operation.
• W ith the engine running, move related connectors and wiring while monitoring
engine operation.
If harness or connector movement affects the data displayed, component/system
operation, or engine operation, inspect and repair the harness/connections as
necessary.
Refer to Electrical Connections or W iring.

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-257
Checks Action
Electrical Connections or W iring Poor electrical connections, terminal tension or wiring problems cause most intermittent. To perform the following inspections:
• Inspect for poor mating of the connector halves, or terminals improperly seated in the
connector body.
• Inspect for improperly formed or damaged terminals. Test for poor terminal tension.
• Inspect for poor terminal to wire connections including terminals crimped over
insulation. This requires removing the terminal from the connector body.
• Inspect for corrosion/water intrusion. Pierced or damaged insulation can allow
moisture to enter the wiring. The conductor can corrode inside the insulation, with
little visible evidence. Look for swollen and stiff sections of wire in the suspect
circuits.
• Inspect for wires that are broken inside the insulation.
• Inspect the harness for pinched, cut or rubbed through wiring.
• Ensure that the wiring does not come in contact with hot exhaust components.
Control Module Power and Grounds
Component Power and Grounds Poor power or ground connections can cause widely varying symptoms.
• Test all control module power supply circuits. Many vehicles have multiple circuits
supplying power to the control module. Other components in the system may have
separate power supply circuits that may also need to be tested. Inspect connections
at the module/component connectors, fuses, and any intermediate connections
between the power source and the module/component. A test lamp or a DMM may
indicate that voltage is present, but neither tests the ability of the circuit to carry
sufficient current. Ensure that the circuit can carry the current necessary to operate
the component.
• Test all control module ground and system ground circuits. The control module may
have multiple ground circuits. Other components in the system may have separate
grounds that may also need to be tested. Inspect grounds for clean and tight
connections at the grounding point. Inspect the connections at the component and in
splice packs, where applicable. Ensure that the circuit can carry the current
necessary to operate the component.
Temperature Sensitivity • An intermittent condition may occur when a component/connection reaches normal
operating temperature. The condition may occur only when the
component/connection is cold, or only when the component/connection is hot.
• If the intermittent is related to heat, review the data for a relationship with the
following: - High ambient temperatures
- Under hood/engine generated heat
- Circuit generated heat due to a poor connection, or high electrical load
- Higher than normal load conditions, towing, etc.
• If the intermittent is related to cold, review the data for the following:
- Low ambient temperatures–In extremely low temperatures, ice may form in a connection or component. Test for water intrusion.
- The condition only occurs on a cold start.
- The condition goes away when the vehicle warms up.
• Information from the customer may help to determine if the trouble follows a pattern
that is temperature related.

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ISUZU KB P190 2007

6E-258 Engine Control System (4JH1)
Checks Action
Electromagnetic Interference (EMI)
and Electrical Noise Some electrical components/circuits are sensitive to EMI or other types of electrical
noise. Inspect for the following conditions:
• A misrouted harness that is too close to high voltage/high current devices such as
injection components, motors, generator etc. These components may induce
electrical noise on a circuit that could interfere with normal circuit operation.
• Electrical system interference caused by a malfunctioning relay, or the engine control
module (ECM) driven solenoid or switch. These conditions can cause a sharp
electrical surge. Normally, the problem will occur when the malfunctioning
component is operating.
• Improper installation of non-factory or aftermarket add on accessories such as lights,
2-way radios, amplifiers, electric motors, remote starters, alarm systems, cell
phones, etc. These accessories may lead to an emission related failure while in use,
but do not fail when the accessories are not in use.
• Test for an open diode across the A/C compressor clutch and for other open diodes.
Some relays may contain a clamping diode.
• Test the generator for a bad rectifier bridge that may be allowing AC noise into the
electrical system.
Incorrect ECM Programming • There are only a few situations where reprogramming a ECM is appropriate:
Important:
DO NOT reprogram the ECM with the SAME software/calibration files that are already
present in the ECM. This is not an effective repair for any type of driveability problem. - A ECM from another vehicle is installed.
- Revised software/calibration files have been released for this vehicle.
• Verify that the ECM contains the correct software/calibration. If incorrect
programming is found, reprogram the ECM with the most current
software/calibration.
Duplicating Failure Conditions • If none of the previous tests are successful, attempt to duplicate and/or capture the
failure conditions.
• An alternate method is to drive the vehicle with the DMM connected to a suspected
circuit. An abnormal reading on the DMM when the problem occurs, may help you
locate the problem.
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 user instructions for more information on the Snapshot function.


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 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.

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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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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