2007 ISUZU KB P190 Electrical

6E-250 ENGINE CONTROL SYSTEM (4JK1/4JJ1)
DTC P156A or P156B (Flash Code 135)
Circuit Description
The ECM monitors the battery voltage on the ECM
main relay voltage feed terminal to make sure that the
voltage stays within the proper range. If the ECM
detects an excessively low or high battery voltage, DTC
P156A or P156B will set.
Condition for Running the DTC • The ignition voltage is more than 9 volts. (DTC P156B)
Condition for Setting the DTC • The ECM detects that the battery voltage feed circuit is less than 8 volts for 20 seconds. (DTC
P156A)
• The ECM detects that the battery voltage feed circuit is more than 16 volts for 5 seconds. (DTC
P156B)
Action Taken When the DTC Sets • The ECM illuminates the SVS lamp when the diagnostic runs and fails. Refer to DTC Type
Definitions for Action Taken When the DTC Sets -
Type C. (Euro 4 Specification) • The ECM illuminates the MIL when the diagnostic
runs and fails. Refer to DTC Type Definitions for
Action Taken When the DTC Sets - Type A.
(Except Euro 4 Specification)
• The ECM limits fuel injection quantity. (DTC P156B)
• The ECM inhibits pilot injection. (DTC P156B)
• The ECM inhibits cruise control. (DTC P156B)
Condition for Clearing the DTC • Refer to DTC Type Definitions for Condition for Clearing the SVS Lamp/ DTC - Type C. (Euro 4
Specification)
• Refer to DTC Type Definitions for Condition for Clearing the MIL/ DTC - Type A. (Except Euro 4
Specification)
Diagnostic Aids • A charging system problem may set this DTC.
• The weakened battery may set DTC P156A.
• Jump starting the vehicle or a battery charger may have set DTC P156B.
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views
Circuit/ System Testing DTC P156A
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 a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine and let idle.
4. Load the electrical system by turning ON the headlights, A/C, etc. while observing the
Battery Voltage parameter with a scan tool.
Does the scan tool indicate more than the specified
value? 10.0 volts
Go to Diagnostic Aids Go to Step 3
3 Test the charging system. Refer to Diagnosis of
The Charging System in the Charging System
Section.
Did you find a charging system problem? —
Go to Step 4 Go to Step 5
4 Repair the charging system. Refer to Diagnosis of
The Charging System in the Charging System
Section.
Did you complete the repair? —
Go to Step 6
—

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ISUZU KB P190 2007

ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-251
Circuit/ System Testing DTC P156B
51. Turn OFF the ignition.
2. Disconnect the ECM harness connector.
3. Inspect for an intermittent, for a poor connection and for corrosion at the harness
connector of the ECM (pin 73 of C-58).
4. Repair the connection(s) 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 a scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine and let idle.
5. Load the electrical system by turning ON the headlights, A/C, etc. while observing the
Battery Voltage parameter with a scan tool.
Does the scan tool indicate more than the specified
value? 10.0 volts
Go to Step 7 Go to Step 3
7 Observe the DTC Information with a scan tool.
Are there any DTCs that you have not diagnosed? —
Go to DTC List System OK
Step
Action Value(s)Yes No
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 Was the vehicle recently jump started or a battery
charger placed on the battery? —
Go to Step 7 Go to Step 3
3 1. Install a scan tool.
2. Start the engine and let idle.
3. Observe the Battery Voltage parameter with the scan tool.
Does the scan tool indicate less than the specified
value? 16.0 volts
Go to Diagnostic Aids Go to Step 4
4 Test the charging system. Refer to Diagnosis of
The Charging System in the Charging System
Section.
Did you find a charging system problem? —
Go to Step 5 Go to Diagnostic
Aids
5 Repair the charging system. Refer to Diagnosis of
The Charging System in the Charging System
Section.
Did you complete the repair? —
Go to Step 6
—

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ISUZU KB P190 2007

ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-255
DTC P1621 (Flash Code 54, 254)
Circuit Description
The electrically erasable & programmable read only
memory (EEPROM) memorizes learning data, VIN data
and immobilzer security information. If the ECM detects
an error in either of their data, this DTC will set.
Condition for Running the DTC • The ignition switch is ON.
Condition for Setting the DTC
Either of following condition is met: • The ECM detects a faulty learning data in its internal EEPROM. (Flash Code 54)
• The ECM detects a faulty VIN data or immobilizer security information in its internal EEPROM. (Flash
Code 254) Action Taken When the DTC Sets
• The ECM illuminates the SVS lamp when the diagnostic runs and fails. Refer to DTC Type
Definitions for Action Taken When the DTC Sets -
Type C. (Euro 4 Specification)
• The ECM illuminates the MIL when the diagnostic runs and fails. Refer to DTC Type Definitions for
Action Taken When the DTC Sets - Type A.
(Except Euro 4 Specification)
• The ECM limits fuel injection quantity. (Flash Code 54)
• The ECM inhibits cruise control. (Flash Code 54)
Condition for Clearing the DTC • Refer to DTC Type Definitions for Condition for Clearing the SVS Lamp/ DTC - Type C. (Euro 4
Specification)
• Refer to DTC Type Definitions for Condition for Clearing the MIL/ DTC - Type A. (Except Euro 4
Specification)
Circuit/ System Testing DTC P1621
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. Ensure that all tool connections are secure.
2. Ensure that programming equipment is operating correctly.
3. Install a scan tool.
4. Turn OFF the ignition for 30 seconds.
5. Turn ON the ignition, with the engine OFF.
6. Monitor the DTC Information with a scan tool.
Does the DTC fail this ignition? —
Go to Step 3 Go to Step 5
3 1. Verify the correct VIN and immobilizer code
are entered into the ECM with a scan tool.
Refer to ECM Replacement.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
Does the DTC fail this ignition? —
Go to Step 4 Go to Step 5
4 Important:
Replacement ECM must be
programmed and learned.
Replace the ECM. Refer to ECM Replacement.
Did you complete the replacement? —
Go to Step 5
—

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ISUZU KB P190 2007

ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-323
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 of
the following are true:
• The ECM and malfunction indicator lamp (MIL)/ service vehicle soon (SVS) lamp are operating
correctly.
• 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 extremely
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 their proper location.
• The vacuum hoses are not split or kinked, and properly connected. Inspect thoroughly for any
type of leak or restriction.
• The air intake ducts are not collapsed or damaged.
• The exhaust pipes are not collapsed or damaged.
• 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 controller area network
(CAN) or other serial data circuit.
Important: The problem may or may not turn ON the
MIL/ SVS lamp 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 order
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 Tech 2 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.
• Freeze Frame/ Failure Record can also aid in locating an intermittent condition. Review and
capture the information in the Freeze Frame/
Failure Record associated with the intermittent
DTC being diagnosed. Drive the vehicle within the
conditions that were present when the DTC
originally set.
• 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 for
more information.
Use the data recording module (DRM) in order to help
detect intermittent conditions. The DRM has ability to
store engine log data when an event of DTC. Maximum
three log data can be stored in the DRM memory. If
more than maximum number of storage is set, oldest
log data is overwritten. However, if same DTC is set
within eight hours that DTC is not stored in the DRM
memory.
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. When there is a space in the DRM
memory, log data is stored in that space. However,
when more than maximum number of storage is set,
oldest log data is overwritten.
Refer to the DRM Users Guide for 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/
SVS lamp with no stored DTC:
• The ECM grounds are loose or dirty. Refer to Engine Controls Schematics.

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ISUZU KB P190 2007

6E-324 ENGINE CONTROL SYSTEM (4JK1/4JJ1)
• The MIL/ SVS lamp circuit intermittently shorted toground
• Electrical system interference caused by a malfunctioning relay, ECM driven solenoid, or
switch. The electrical component can cause a
sharp electrical surge. Normally, the problem will
occur when the malfunctioning component is
operating.
• There are any open diodes.
Important: The following symptom tables contain
groups of 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
• High Idle Speed
•Cuts Out
• Surges
• Lack of Power, Sluggishness or Sponginess
• Hesitation, Sag or Stumble
• Abnormal Combustion Noise
• Poor Fuel Economy
• Excessive Smoke (Black Smoke)
• Excessive Smoke (White Smoke)

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ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-325
Intermittent Conditions
ChecksAction
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.
• With 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.
Electrical Connections or Wiring Poor electrical connections, terminal tension or wiring problems cause most intermittent. To perform the following inspections:
• Poor mating of the connector halves, or terminals improperly seated in the connector body.
• Improperly formed or damaged terminals. Test for poor terminal tension.
• Poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body.
• 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.
• Wires that are broken inside the insulation.
• 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.

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6E-326 ENGINE CONTROL SYSTEM (4JK1/4JJ1)
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.
• Freeze Frame, Failure Records or Snapshot Data may help with this type of intermittent conditions, where applicable.
• If the intermittent is related to heat, review the data for a relationship with the following:
- High ambient temperatures.
- Underhood/ 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 aconnection 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.
Electromagnetic Interference (EMI)
and Electrical Noise Some electrical components/ circuits are sensitive to EMI or other types of electrical
noise. Inspect 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 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 any 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:
- An ECM from another vehicle is installed.
- Revised software/ calibration files have been released for this vehicle.
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.
• 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.
• Freeze Frame/ Failure Records data, where applicable, contains the conditions that were present when the DTC set.
- Review and record Freeze Frame/ Failure Records data.
- Operate the vehicle under the same conditions that were noted in Freeze Frame/ Failure Records data, as closely as possible. The vehicle must also be
operating within the Conditions for Running the DTC. Refer to Conditions for
Running the DTC in the supporting text of the DTC being diagnosed.
• 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.
Checks
Action

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ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-329
Air Intake System ChecksInspect 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

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