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Isuzu KB P190. Manual - part 600

6E–230

ENGINE DRIVEABILITY AND EMISSIONS

Using the DVM and check the Tacho output circuit.
Breaker box is available:

1. Ignition “Off”, engine “Off”.

2. Install the breaker box as type A. (ECM

disconnected) Refer to 6E-88 page.

3. Disconnect the meter connector.

4. Check the circuit for open or short to ground

circuit.

Was the problem found?

Breaker box is not available:

1. Ignition “Off”, engine “Off”.

2. Disconnect the ECM connector.

3. Disconnect the meter connector.

4. Check the circuit for open or short to ground

circuit.

Was the problem found?

—

Repair faulty

harness and

verify repair

Go to Step 7

Using the DVM and check the Tacho output circuit.

1. Ignition “On”, engine “Off”.

2. Disconnect the meter connector.

3. Check the circuit for short to power supply circuit.

Was the DVM indicated specified value?

Less than 1V

Go to Step 8

Repair faulty

harness and

verify repair

Check any accessory parts which may cause electric
interference or magnetic interference.
Was the problem found?

—

Remove the

accessory parts

and verify repair

Go to Step 9

Step

Action

Value(s)

Yes

J2-25

Breaker Box

B-24

C-56(J2)

B-24

ENGINE DRIVEABILITY AND EMISSIONS

6E–231

Replace the Tacho meter.
Was the problem solved?

—

Verify repair

Go to Step 10

Is the ECM programmed with the latest software
release?
If not, download the latest software to the ECM using
the “SPS (Service Programming System)”.
Was the problem solved?

—

Verify repair

Go to Step 11

Replace the ECM.
Is the action complete?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobilizer system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobilizer System-ECM replacement” for
the ECM/Immobilizer linking procedure.

—

Verify repair

—

Step

Action

Value(s)

Yes

6E–232

ENGINE DRIVEABILITY AND EMISSIONS

SYMPTOM DIAGNOSIS

PRELIMINARY CHECKS

Before using this section, perform the “On-Board
Diagnostic (OBD) System Check” and verify all of the
following items:

• The engine control module (ECM) and malfunction

indicator lamp (MIL = Check Engine Lamp) are
operating correctly.

• There are no Diagnostic Trouble Code(s) stored.

• Tech 2 data is within normal operating range. Refer to

Typical Scan Data Values.

• Verify the customer complaint and locate the correct

symptom in the table of contents. Perform the
procedure included in the symptom chart.

VISUAL/PHYSICAL CHECK

Several of the symptom procedures call for a careful
visual/physical check. This can lead to correcting a
problem without further checks and can save valuable
time. This check should include the following items:

• ECM grounds for cleanliness, tightness and proper

location.

• Vacuum hoses for splits, kinks, and proper

connection, shown on the “Emission Control System
Schematics”. Check thoroughly for any type of leak or
restriction.

• Air intake ducts for collapsed or damaged areas.

• Air leaks at throttle body mounting area, manifold

absolute pressure (MAP) sensor and intake manifold
sealing surfaces.

• Ignition wires for cracking, harness, and carbon

tracking.

• Wiring for proper connections, pinches and cuts.

INTERMITTENT

Important: An intermittent problem may or may not turn
on the malfunction indicator lamp (MIL) or store a
Diagnostic Trouble Code. Do NOT use the Diagnostic
Trouble Code (DTC) charts for intermittent problems.
The fault must be present to locate the problem.
Most intermittent problems are cased by faulty electrical
connections or wiring. Perform a careful visual/physical
check for the following conditions.

• Poor mating of the connector halves or a terminal not

fully seated in the connector (backed out).

• Improperly formed or damaged terminal.

• All connector terminals in the problem circuit should

be carefully checked for proper contact tension.

• Poor terminal-to-wire connection. This requires

removing the terminal form the connector body to
check.

• Ignition coils shorted to ground and arcing at ignition

wires or plugs.

• MIL (Check Engine Lamp) wire to ECM shorted to

ground.

• Poor ECM grounds. Refer to the ECM wiring

diagrams.

Road test the vehicle with a Digital Multimeter
connected to a suspected circuit. An abnormal voltage
when the malfunction occurs is a good indication that
there is a fault in the circuit being monitored.
Using Tech 2 to help detect intermittent conditions. The
Tech 2 has several features that can be used to located
an intermittent condition.

An intermittent MIL (Check Engine Lamp) with no stored
Diagnostic Trouble Code may be caused by the
following:

• Ignition coil shorted to ground and arcing at ignition

wires or plugs.

• MIL (Check Engine Lamp) wire to ECM short to

ground.

• Poor ECM grounds. Refer to the ECM wiring

diagrams.

Check for improper installation of electrical options such
as light, cellular phones, etc. Check all wires from ECM
to the ignition control module for poor connections.
Check for an open diode across the A/C compressor
clutch and check for other open diodes (refer to wiring
diagrams in Electrical Diagnosis).

If problem has not been found, refer to ECM connector
symptom tables.

• Check the “Broadcast Code” of the ECM, and

compare it with the latest Isuzu service bulletins and/
or Isuzu EEPROM reprogramming equipment to
determine if an update to the ECM’s reprogrammable
memory has been released.

To check the “Broadcast Code”, connect the Tech 2,
then look for “ID info.” then select “Broadcast Code”.
This should display a 4 character code, such as “XBYA”
(example only).
This identifies the contents of the reprogrammable
software and calibration contained in the ECM.
If the “Broadcast Code” is not the most current
available, it is advisable to reprogram the ECM’s
EEPROM memory, which may either help identify a
hard-to find problem or may fix the problem.
The Service Programming System (SPS) will not allow
incorrect software programming or incorrect calibration
changes.

ENGINE DRIVEABILITY AND EMISSIONS

6E–233

ENGINE CRANKS BUT WILL NOT RUN

DEFINITIONS: Engine cranks, but will not run. (The engine never start.)
NOTE: The replacement ECM must be programmed. Refer to section of the Service Programming System (SPS) in
this manual. Following ECM programming, the immobilizer system (if equipped) must be linked to the ECM.
Refer to section 11 “Immobilizer System-ECM replacement” for the ECM/Immobilizer linking procedure.
NOTE: The vehicle with immobilizer system, this system may be activated. Check the immobilizer system diagosis.

Step

Action

Value(s)

Yes

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to Step 2

Go to OBD

System Check

1. Perform a bulletin search.

2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

—

Verify repair

Go to Step 3

Was a visually/physical check performed?

—

Go to Step 4

Go to Visual /

physical Check.

Check the “Ignition coil” fuse (15A) and “ECM” fuse
(15A).
Was a fuse blown?

—

Verify repair

Go to Step 5

1. Ignition ON

2. Use a DVM to verify that battery voltage at the

ignition coil fuse, and the ECM fuse.

Was battery voltage presented at the fuses?

—

Go to Step 6

Verify & repair

1. Visually/physically inspect for the following

conditions:

• Restriction of air intake system. Check for a

restricted air filter element, or foreign objects
blocking the air intake system.

• Check for objects blocking the IAC passage or

throttle bore, excessive deposits in the throttle
bore and on the throttle plate.

• Check for a condition that causes a large

vacuum leak, such as an incorrectly installed or
faulty crankcase ventilation hose/brake booster
hose.

Was a problem found?

—

Verify repair

Go to Step 7

1. Using a Tech 2, display the IAC value.

2. Check for a faulty, plugged, or sticking IAC

operation.

Was the problem found?

—

Verify repair

Go to Step 8

1. Using a Tech 2, display the MAP sensor value.

2. Check for a faulty, plugged, or incorrectly installed

MAP sensor.

Was the problem found?

—

Verify repair

Go to Step 9

If oscilloscope is available, check the wave form of the
CKP signal.
Was the correct wave form found?

—

Go to Step 12

Go to Step 10

Check the CKP sensor wire for open or short circuit.
Was a problem found?

—

Verify repair

Go to Step 11

Replace CKP sensor.
Is there still problem?

—

Replace pulsar

ring.

Verify repair

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