engine ISUZU TF SERIES 2004 Workshop Manual

6E–104 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Breaker Box Connection Type B
Breaker box connection type B, check for “short to
power supply circuit” and “power, signal voltage check”
between the engine control module (ECM) and
electrical components.


(1) Engine Control Module (ECM)
(2) Harness Adapter
(3) Breaker Box(4) Digital Voltage Meter
(5) ECM - Harness Adapter Connection

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–105
ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
Circuit Description
The on-board diagnostic system check is the starting
point for any driveability complaint diagnosis. Before
using this procedure, perform a careful visual/physical
check of the ECM and engine grounds for cleanliness
and tightness.
The on-board diagnostic system check is an organized
approach to identifying a problem created by an
electronic engine control system malfunction.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed-through wire insulation or a wire broken inside
the insulation. Check for poor connections or a
damaged harness. Inspect the ECM harness and
connector for improper mating, broken locks, improperly
formed or damaged terminals, poor terminal-to-wireconnection, and damaged harness.
Test Description
Number(s) below refer the step number(s) on the
Diagnostic Chart:
1. The Check Engine Lamp (MIL) should be ON steady
with the ignition “On”, engine “Off”. If not, “No Check
Engine Lamp (MIL)” chart should be used to isolate the
malfunction.
2. Checks the Class 2 data circuit and ensures that the
ECM is able to transmit serial data.
3. This test ensures that the ECM is capable of
controlling the Check Engine Lamp (MIL) and the Check
Engine Lamp (MIL) driver circuit is not shorted to
ground circuit.
4. If the engine will not start, “Engine Cranks But Will
Not Run” chart should be used to diagnose the fault.

6E–106 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
6. The Tech2 parameters which is not within the typical
range may help to isolate the area which is causing the
problem.12. This vehicle is equipped with ECM which utilizes an
electrically erasable programmable read only memory
(EEPROM).
On-Board Diagnostic (OBD) System Check
Step Action Value(s) Yes No
11. Ignition “On”, engine “Off”.
2. Check the “CHECK ENGINE” lamp (MIL).
Does the “CHECK ENGINE” lamp turn “On”?—Go to Step 2Go to No
CHECK
ENGINE Lamp
21. Using the Tech 2, ignition “On” and engine “Off”.
2. Attempt to display “Data Display” with the Tech 2.
Does the Tech 2 display engine data? —Go to Step 3Go to Step 7
31. Using the Tech 2, ignition “On” and engine “Off”.
2. Select the “Miscellaneous Test” and perform the
“Check Light” in “Lamps”.
3. Operate the Tech 2 in accordance with the Tech 2
instructions.
Does the “CHECK ENGINE” lamp turn “Off”? —Go to Step 4Go to CHECK
ENGINE LAMP
On Steady
4Attempt to start the engine.
Does the engine start and continue to “Run”?
—Go to Step 5Go to Engine
Cranks But Will
Not Run
51. Using the Tech 2, ignition “On” and engine “Off”.
2. Select the “Read DTC Infor As Stored By ECU” in
“Diagnostic Trouble Code”.
3. Are any DTCs stored?—Go to DTC
ChartGo to Step 6
6Compare typical scan data values displayed on the
Te c h 2 “Data Display”.
Are the displayed values within the range?—Refer to
SYMPTOM
DIAGNOSISRefer to
TYPICAL
SCAN DATA
7Using the DVM and check the data link connector
power supply circuit.
1. Ignition “Off”, engine “Off”.
2. Check the circuit for open circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 8
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4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–107
8Using the DVM and check the data link connector
ground circuit.
1. Ignition “Off”, engine “Off”.
2. Check the circuit for open circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 9
9Using the DVM and check the data link connector
ground circuit.
1. Ignition “On”, engine “Off”.
2. Check the circuit for short to power supply circuit.
Was the DVM indicated specified value?
Less than 1V Go to Step 10Repair faulty
harness and
verify repair
10Using the DVM and check the data link connector
communication circuit.
1. Ignition “On”, engine “Off”.
2. Check the circuit for short to power supply circuit.
Was the DVM indicated fix ed battery voltage?
—Repair faulty
harness and
verify repair Go to Step 11 Step Action Value(s) Yes No
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6E–108 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
11Using the DVM and check the data link connector
communication circuit.
1. Ignition “Off”, engine “Off”.
2. Disconnect the ECM connector.
3. Check the circuit for open or short to ground
circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 12
12Is 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 13
13Replace 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.—Veri fy repai r— Step Action Value(s) Yes No





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4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–109
NO CHECK ENGINE LAMP (MIL)
Circuit Description
The check engine lamp should be illuminated and
steady for about five seconds with the ignition “ON” and
the engine stopped. Ignition feed voltage is supplied to
the check engine lamp bulb through the meter fuse.
The Engine Control Module (ECM) turns the check
engine lamp “ON” by grounding the check engine lamp
driver circuit.
Diagnostic Aids
An intermittent check engine lamp may be cased by a
poor connection, rubbed-through wire insulation, or awire broken inside the insulation. Check for the
following items:
Inspect the ECM harness and connections for
improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wire connection,
and damaged harness.
If the engine runs OK, check for a faulty light bulb, an
open in the check engine lamp driver circuit, or an
open in the instrument cluster ignition feed.
If the engine cranks but will not run, check for an
open ECM ignition or battery feed, or a poor ECM to
engine ground.

6E–110 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
No Check Engine Lamp (MIL)
Step Action Value(s) Yes No
1 Check the meter fuse (15A).
If the fuse is burnt out, repair as necessary.
Was the problem found?—Verify repair Go to Step 2
2 Using the DVM and check the “CHECK ENGINE”
lamp circuit.
1. Ignition “Off”, engine “Off”.
2. Disconnect the ECM connector.
3. Ignition “On”.
4. Check the circuit for open circuit.
Was the DVM indicated specified value?
10-14.5V Go to Step 5Go to Step 3
3 Check the “CHECK ENGINE” lamp bulb.
If the bulb is burnt out, repair as necessary.
Was the problem found?—Verify repair Go to Step 4
4 Using the DVM and check the “CHECK ENGINE”
lamp circuit.
1. Ignition “Off”, engine “Off”.
2. Disconnect the meter connector and ECM
connector.
3. Check the circuit for open circuit.
Was the problem found?
—Verify repair Go to Step 5
5 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 6
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4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–111
6 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.—Veri fy repai r— Step Action Value(s) Yes No

6E–112 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
CHECK ENGINE LAMP (MIL) “ON” STEADY
Circuit description
The check engine lamp should always be illuminated
and steady for about five seconds with ignition “ON” and
the engine stopped. Ignition feed voltage is supplied
directly to the check engine lamp indicator. The Engine
Control Module (ECM) turns the check engine lamp
“ON” by grounding the check engine lamp driver circuit.
The check engine lamp should not remain “ON” with the
engine running and no DTC(s) set. A steady check
engine lamp with the engine running and no DTC(s)
suggests a short to ground in the check engine lamp
driver circuit.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed-through wire insulation, or a wire broken inside
the insulation. Check for the following items:
Poor connection or damaged harness – Inspect the
ECM harness and connectors for improper mating,
broken locks, improperly formed or damaged
terminals, poor terminal-to-wire connection, and
damaged harness.

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–11 3
Check Engine Lamp (MIL) On Steady
Step Action Value(s) Yes No
1 1. Ignition “Off”, engine “Off”.
2. Disconnect the ECM connector.
3. Ignition “On”.
Was the “CHECK ENGINE” lamp turned on?—Go to Step 2 Go to Step 4
2 Using the DVM and check the “CHECK ENGINE”
lamp circuit.
1. Ignition “Off”, engine “Off”.
2. Disconnect the meter connector and ECM
connector.
3. Check the circuit for short to ground circuit.
Was the problem found?
—Veri fy repai rGo to Step 3
3 Replace the meter assembly.
Is the action complete?—Veri fy repai r—
4 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?—Veri fy repai rGo to Step 5
5 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.—Veri fy repai r—
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