Isuzu KB P190. Service manual - part 415

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-43

Diagnostic Information and Procedures

Engine Control System Check Sheet

6E-44   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

Diagnostic Starting Point - Engine Controls

Begin the system diagnosis with Diagnostic System
Check - Engine Controls.  The Diagnostic System
Check - Engine Controls will provide the following
information:

• The identification of the control modules which

command the system.

• The ability of the control modules to communicate

through the serial data circuit.

• The identification of any stored diagnostic trouble

codes (DTCs) and the their statuses.

The use of the Diagnostic System Check - Engine
Controls will identify the correct procedure for
diagnosing the system and where the procedure is
located.

Important: Engine Control System Check Sheet must
be used to verify the complaint vehicle, you need to
know the correct (normal) operating behavior of the
system and verify that the customer complaint is a valid
failure of the system.

Reading Flash Diagnostic Trouble Codes (DTC)

The provision for communicating with the ECM is the
Data Link Connector (DLC). The DTC(s) stored in the
ECM memory can be read either through a hand-held
diagnostic scanner such as Tech 2 plugged into the
DLC or by counting the number of flashes of the
malfunction indicator lamp (MIL) or the service vehicle
soon (SVS) lamp when the diagnostic test terminal of
the DLC is grounded. The DLC terminal "1" (diagnostic
request) is pulled "Low" (grounded) by jumped to DLC
terminal "4", which is a ground wire. Once terminals "1"
and "4" have been connected, turn the ignition switch
ON, with the engine OFF. The MIL (except Euro 4
specification) or the SVS lamp (Euro 4 specification)
will indicate a DTC three times is a DTC is present and
history. If more than one DTC has been stored in the
ECM's memory, the DTCs will be output set order with
each DTC being displayed three times. The flash DTC
display will continue as long as the DLC is shorted.

RTW76ESF000301

ON

OFF

ON

OFF

1.2

3.2

2.6

2.6

2nd digit number

1st digit number

3.2

0.6

2

1.2

0.6

0.6

0.6

0.3

0.3

0.3

0.3

0.3

0.3

0.3

0.3

Example:DTC 23 stored

Unit: Second

Example:DTC 225 stored

3rd digit

number

2nd digit number

1st digit number

0.6

0.6

0.6

0.6

0.6

0.6

0.6

0.6

3

0.3

0.3

1.2

1.2

2

2

5

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-45

Diagnostic System Check - Engine Controls

Description

The Diagnostic System Check - Engine Controls is an
organized approach to identifying a condition that is
created by a malfunction in the electronic engine
control system. The Diagnostic System Check must be
the starting point for any driveability concern. The
Diagnostic System Check directs the service technician
to the next logical step in order to diagnose the
concern. Understanding and correctly using the
diagnostic table reduces diagnostic time, and prevents
the replacement of good parts.

Test Description

The numbers below refer to the step numbers on the
diagnostic table.
2. Lack of communication may be because of a partial
or a total malfunction of the serial data circuit.
7. The presence of DTCs which begin with U, indicate
that some other module is not communicating.
10. If there are other modules with DTCs set, refer to
the DTC list. The DTC list directs you to the appropriate
diagnostic procedure.  If the control module stores
multiple DTCs, diagnose the DTCs in the following
order:

• Component level DTCs, such as sensor DTCs,

solenoid DTCs, actuator DTCs, and relay DTCs.
Diagnose the multiple DTCs within this category in
numerical order.  Begin with the lowest numbered
DTC, unless the diagnostic table directs you
otherwise.

Diagnostic System Check Engine Controls
Important:

• DO NOT perform this diagnostic if there is not a

driveability concern, unless another procedure
directs you to this diagnostic.

• Before you proceed with diagnosis, search for

applicable service bulletins.

• Unless a diagnostic procedure instructs you, DO

NOT clear the DTCs.

• If there is a condition with the starting system, refer

to the starting system section in the engine
mechanical.

• Ensure the battery has a full charge.

• Ensure the battery cables (+) (-) are clean and

tight.

• Ensure the ECM grounds are clean, tight, and in

the correct location.

• Ensure the ECM harness connectors are clean

and correctly connected.  DO NOT attempt to
crank the engine with ECM harness connectors
disconnect.

• Ensure the ECM terminals are clean and correctly

mating.

• Ensure the fuel injector ID code data is correctly

programmed in to the ECM.

• Ensure the immobilizer security information is

correctly programmed into the ECM and
immobilizer control unit (ICU).

• If there are fuel system DTC’s (P0087, P0088,

P0089, P0093, P1093 or P1094), diagnose sensor
DTCs, solenoid DTCs, actuator DTCs and relay
DTCs first.

Diagnostic System Check - Engine Controls

Step

Action

Value(s)

Yes

No

1

Install a scan tool.

Does the scan tool turn ON?

—

Go to Step 2

Go to Scan Tool 

Does Not Power Up

2

1.

Turn ON the ignition, with the engine OFF.

2.

Attempt to establish communication with the
listed control modules.

• ECM

• Immobilizer control unit (ICU) (If so

equipped)

• Transmission control module (TCM)

(AISIN A/T only)

Does the scan tool communicate with all the listed
control modules?

—

Go to Step 3

Go to Scan Tool 

Does Not 

Communicate with 

CAN Device

6E-46   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

3

Notice: If an immobilizer system is active the ECM
will disable the fuel injection causing the engine to
stall immediately after starting and energize the
starter cut relay to disable cranking.
Attempt to crank the engine.

Does the engine crank?

—

Go to Step 4

Go to Step 5

4

Attempt to start the engine.

Does the engine start and idle?

—

Go to Step 6

Go to Engine 

Cranks but Does 

Not Run

5

Does the scan tool display ECM DTCs P0615,
P0633, P161B or U0167?

—

Go to Applicable 

DTC

Problem is relating 

to starting system. 

Refer to the 

applicable 

diagnostic chart in 

starting system

6

Select the DTC display function for the following
control modules:

• ECM
• ICU (If so equipped)

• TCM (AISIN A/T only)

Does the scan tool display any DTCs?

—

Go to Step 7

Go to Step 11

7

Does the scan tool display DTCs which begin with
U or other control module communication fault
DTCs?

—

Go to Applicable 

DTC

Go to Step 8

8

Does the scan tool display ECM DTCs P0601,
P0602, P0604, P0606 or P1621?

—

Go to Applicable 

DTC

Go to Step 9

9

Does the scan tool display ECM DTCs P0562 or
P0563, P156A or P156B?

—

Go to Applicable 

DTC

Go to Step 10

10

Is there any other code in any controller that has
not been diagnosed?

—

Go to Applicable 

DTC

Go to Step 11

11

Is the customer’s concern with the automatic
transmission?

—

Go to Diagnostic 

System Check - 

Transmission 

Controls

Go to Step 12

12

Is the customer’s concern with the immobilizer
system?

—

Go to Diagnostic 

System Check - 

Immobilizer 

Controls

Go to Step 13

13

1.

Review the following symptoms.

2.

Refer to the applicable symptom diagnostic
table:

• Hard Start

• Rough, Unstable, or Incorrect Idle and

Stalling

• High Idle Speed

• Cuts  Out

• Surges

• Lack of Power, Sluggishness, or

Sponginess

• Hesitation, Sag, Stumble

• Abnormal Combustion Noise

• Poor Fuel Economy

• Excessive Smoke (Black Smoke)

• Excessive Smoke (White Smoke)

Did you find and correct the condition?

—

System OK

Go to Intermittent 

Conditions

Step

Action

Value(s)

Yes

No