check engine ISUZU TF SERIES 2004 Workshop Manual

ENGINE DRIVEABILITY AND EMISSIONS 6E–89
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.
51
432
(1) Engine Control Module (ECM)
(2) Harness Adapter
(3) Breaker Box(4) Digital Voltage Meter
(5) ECM - Harness Adapter Connection

6E–90 ENGINE DRIVEABILITY AND EMISSIONS
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-wire
connection, 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.
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).

ENGINE DRIVEABILITY AND EMISSIONS 6E–91
ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
Step Action Value(s) Yes No
1 1. 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
2 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Attempt to display “Engine Data” w i t h t h e T e c h 2 .
Does the Tech 2 display “Engine Data” and “O
2Sensor Data”? —Go to Step 3Go to Step 7
3 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Select the “Miscellaneous Test” and perform the
“Malfunction Indicator Lamp” 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
4 Attempt to start the engine.
Does the engine start and continue to “Run”?
—Go to Step 5Go to Engine
Cranks But Will
Not Run
5 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Select the “Read DTC Infor By Priority” in
“Diagnostic Trouble Code”.
3. Are any DTCs stored?—Go to DTC
ChartGo to Step 6
6 Compare typical scan data values displayed on the
Te c h 2 “Engine Data” and “O
2 Sensor Data”.
Are the displayed values within the range?—Refer to
SYMPTOM
DIAGNOSISRefer to
TYPICAL
SCAN DATA
7 Using 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
8 Using 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
V
16
B58
5 4B58

6E–92 ENGINE DRIVEABILITY AND EMISSIONS
9 Using 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
10 Using 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 battery voltage?
—Repair faulty
harness and
verify repair Go to Step 11
11 Using 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
12 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 13 Step Action Value(s) Yes No
VV
5 4B58
V
B-58

C-56(J2)



B- 58


6E–94 ENGINE DRIVEABILITY AND EMISSIONS
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.
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

ENGINE DRIVEABILITY AND EMISSIONS 6E–95
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
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
V
32C56(J2)
3217C56(J2)B24

6E–96 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.
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 2Go to Step 4

ENGINE DRIVEABILITY AND EMISSIONS 6E–97
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?
—Verify repair Go 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?—Verify repair Go 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— Step Action Value(s) Yes No
32C56(J2)

6E–98 ENGINE DRIVEABILITY AND EMISSIONS
FUEL METERING SYSTEM CHECK
Some failures of the fuel metering system will result in
an “Engine Cranks But Will Not Run” symptom. If this
condition ex ists, refer to the Cranks But Will Not Run
chart. This chart will determine if the problem is caused
by the ignition system, the ECM, or the fuel pump
electrical circuit.
Refer to Fuel System Electrical Test for the fuel system
wiring schematic.
If there is a fuel delivery problem, refer to Fuel System
Diagnosis, which diagnoses the fuel injectors, the fuel
pressure regulator, and the fuel pump.
Followings are applicable to the vehicles with
closed Loop System:
If a malfunction occurs in the fuel metering system, it
usually results in either a rich HO2S signal or a lean
HO2S signal. This condition is indicated by the HO2S
voltage, which causes the ECM to change the fuel
calculation (fuel injector pulse width) based on the
HO2S reading. Changes made to the fuel calculation
will be indicated by a change in the long term fuel trim
values which can be monitored with a Scan Tool. Ideal
long term fuel trim values are around 0%; for a lean
HO2S signal, the ECM will add fuel, resulting in a fuel
trim value above 0%. Some variations in fuel trim values
are normal because all engines are not ex actly the
same. If the evaporative emission canister purge is 02
status may be rich condition. 02 status indicates the
lean condition, refer to DTC P1171 for items which can
cause a lean HO2S signal.
FUEL INJECTOR COIL TEST PROCEDURE
AND FUEL INJECTOR BALANCE TEST
PROCEDURE
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
2. Relieve the fuel pressure by connecting 5-8840-
0378-0 T-Joint to the fuel pressure connection on the
fuel rail.
Caution: In order to reduce the risk of fire and
personal injury, wrap a shop towel around the
fuel pressure connection. The towel will absorb
any fuel leakage that occurs during the
connection of the fuel pressure gauge. Place the
towel in an approved container when the
connection of the fuel pressure gauge is
complete.
Place the fuel pressure gauge bleed hose in an
approved gasoline container.
With the ignition switch OFF open the valve on the
fuel pressure gauge.
3. Record the lowest voltage displayed by the DVM
after the first second of the test. (During the first
second, voltage displayed by the DVM may be
inaccurate due to the initial current surge.)
Injector Specifications:
The voltage displayed by the DVM should be
within the specified range.
The voltage displayed by the DVM may increase
throughout the test as the fuel injector windings
warm and the resistance of the fuel injector
windings changes.Resistance OhmsVoltage Specification at
10°C-35°C (50°F-95°F)
11.8-12.6 5.7-6.6

ENGINE DRIVEABILITY AND EMISSIONS 6E–99
An erratic voltage reading (large fluctuations in
voltage that do not stabilize) indicates an
intermittent connection within the fuel injector.
5. Injector Specifications:7. The Fuel Injector Balance Test portion of this chart
(Step 7 through Step 11) checks the mechanical (fuel
delivery) portion of the fuel injector. An engine
cooldown period of 10 minutes is necessary in order
to avoid irregular fuel pressure readings due to “Hot
Soak” fuel boiling.
Injector Coil Test Procedure (Steps 1-6) and Injector Balance Test Procedure (Steps 7-11)
NOTE: These figures are ex amples only.Highest Acceptable Voltage
Reading Above/Below
35°C/10°C (95°F/50°F)Acceptable
Subtracted Value
9.5Volts 0.6Volt
CYLINDER
1234
1st Reading (1) 296kPa
(43psi)296kPa
(43psi)296kPa
(43psi)296kPa
(43psi)
2nd Reading (2) 205kPa
(29psi)205kPa
(29psi)196kPa
(28psi)274kPa
(39psi)
Amount of Drop
(1st Reading-2nd Reading)91kPa
(14psi)91kPa
(14psi)100kPa
(15psi)22kPa
(4psi)
Av. Drop = 166kPa/24psi

10kPa/1.5psi
= 156 - 176kPa or
22.5 - 25.5psiFaulty, Lean
(Too Little Fuel
Drop)Faulty, Lean
(Too Little Fuel
Drop)Faulty, Lean
(Too Little Fuel
Drop)Faulty, Lean
(Too Little Fuel
Drop)