2004 ISUZU TF SERIES check engine light

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–89
18 Brake Switch 2 Active/
InactiveInactive Inactive Inactive This displays operating status of the brake switch. This
should display "Active" when the brake pedal is stepped
on.
19 Clutch Sw itch Activ e /
InactiveInactive Inactive Inactive This displays operating status of the clutch switch. This
should display "Active" when the clutch pedal is stepped
on.
20 Neutra l Switch On/Off On On On This displa ys o pe rating status of the neutra l switch. This
should display "On" when the gear position is neutral.
21 A/C Informa tion
SwitchActive 12V/
Inactive 0VInactive 0V Inactive 0V Inactive 0V This displays the air conditioner request signal. This
should display "Active 12V" when the air conditioner switch
is switched on.
22 Dia gnostic Re quest Activ e 0V/
Inactive 12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis display s the dia gnostic reque st signal. This sho uld
display "Inactive 12V" when the Tech 2 is connected.
23 System Voltage V 10 - 14 10 - 14 10 - 14 This displays the system voltage measured by the ECM at
ignition feed.
24 Ma in Re la y Activ e /
InactiveActive Active Active This displays operating status for the ECM main relay. This
should display "Active" when the key switch is turned on
and while engine is running.
25 Glow Time Relay Activ e 0V/
Inactive12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis displays operating status for the glow relay. This
should display "Inactive 12V" when the engine is warm
uppe d.
26 Check Engine Light On/Off Off Off Off This displays operating status for the Check Engine Lamp.
This should display "On" when the Check Engine Lamp is
turned on.
27 Glow Time Telltale On/Off Off Off Off This displays operating status for the glow indicator lamp.
This sho uld display "On" whe n the glo w la mp is turne d o n.
28 Desired Engine Idle
Speedrpm 730 730 730 The desired engine idle speed that the ECM commanding.
The ECM compensates for various engine loads based on
engine coolant temperature.
29 A/C Re que st Activ e 0V/
Inactive 12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis displays operating status of the A/C compressor. This
should display "Active 0V" when the compressor relay is
operated.
30 Immo bilize r Activ e /
InactiveInactive Inactive Inactive This should display "Inactive" when the immobilizer is
correctly operated.
31 Immo bilize r Signal Rece iv ed/
Not
Rece iv edNo t
Receive dNo t
Re ceive dNot
Re ce iv e dThis sho uld displa y "No t Receive d" whe n the immo bilize r is
not activated.
32 Immo bilize r Function
ProgrammedYes/ No Yes Yes Yes This should display "Yes" when the immobilizer is correctly
programmed.
33 EGR Pulse Ratio
(Ex ha ust Ga s
Recirculatio n)% 70 70 70 This displays the duty signal from the ECM to control the
EGR flow amount. Tech 2 Parameter Units Idle 1500rpm 2000rpm Description

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–91
18 Brake Switch 2 Active/
InactiveInactive Inactive Inactive This displays operating status of the brake switch. This
should display "Active" when the brake pedal is stepped
on.
19 Clutch Switch (M/T
On ly )Active/
InactiveInactive Inactive Inactive This displays operating status of the clutch switch. This
should display "Active" when the clutch pedal is stepped
on.
20 Neutra l Switch On/Off On On On This displa ys o pe rating status of the neutra l switch. This
should display "On" when the gear position is neutral (M/T)
or P, N positio n (A/T).
21 A/C Informa tion
SwitchActive 12V/
Inactive 0VInactive 0V Inactive 0V Inactive 0V This displays the air conditioner request signal. This
should display "Active 12V" when the air conditioner switch
is switched on.
22 Dia gnostic Re quest Activ e 0V/
Inactive 12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis displays the diagnostic request signal. This should
display "Inactive 12V" when the Tech 2 is connected.
23 System Voltage V 10 - 15 10 - 15 10 - 15 This displays the system voltage measured by the ECM at
ignition feed.
24 Ma in Re la y Activ e /
InactiveActive Active Active This displays operating status for the ECM main relay. This
should display "Active" when the key switch is turned on
and while engine is running.
25 Glow Time Relay Activ e 0V/
Inactive12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis displays operating status for the glow relay. This
should display "Inactive 12V" when the engine is warm
uppe d.
26 Check Engine Light On/Off Off Off Off This displays operating status for the Check Engine Lamp.
This should display "On" when the Check Engine Lamp is
turned on.
27 Glow Time Telltale On/Off Off Off Off This displays operating status for the glow indicator lamp.
This sho uld display "On" whe n the glo w la mp is turne d o n.
28 Desired Engine Idle
Speedrpm 700 700 700 The desired engine idle speed that the ECM commanding.
The ECM compensates for various engine loads based on
engine coolant temperature.
29 A/C Re que st Activ e 0V/
Inactive 12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis displays operating status of the A/C compressor. This
should display "Active 0V" when the compressor relay is
operated.
30 Immo bilize r Activ e /
InactiveInactive Inactive Inactive This should display "Inactive" when the immobilizer is
correctly operated.
31 Immo bilize r Signal Rece iv ed/
Not
Rece iv edNo t
Receive dNot
Re ceive dNot
Re ce iv e dThis sho uld displa y "No t Receive d" whe n the immo bilize r is
not activated.
32 Immo bilize r Function
ProgrammedYes/ No Yes Yes Yes This should display "Yes" when the immobilizer is correctly
programmed.
33 EGR Pulse Ratio
(Ex ha ust Ga s
Recirculatio n)% 85 - 90 85 - 90 85 - 90 This displays the duty signal from the ECM to control the
EGR flow amount. Tech 2 Parameter Units Idle 1500rpm 2000rpm Definition

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
V
B-58

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–254 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
or low, DTC P0560 (Symptom Code A) will be stored.
Diagnostic Aids
An intermittent may be caused by the following:
Poor connections.
Misrouted harness.
Rubbed through wire insulation.
Broken wire inside the insulation.
Check for the following conditions:Poor connection at ECM and PSG-Inspect harness
connectors for backed out terminals, improper
mating, broken locks, improperly formed or damaged
terminals, and poor terminal to wire connection.
Damaged harness-Inspect the wiring harness for
damage. If the harness appears to be OK, observe
the “System Voltage” display on the Tech2 while
moving connectors and wiring harness related to the
sensor.
Diagnostic Trouble Code (DTC) P0560 (Symptom Code 1) (Flash Code 35)
System Voltage Too High
Step Action Value(s) Yes No
1Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go to On Board
Diagnostic
(OBD) System
Check
2 1. Connect the Tech 2.
2. Review and record the failure information.
3. Select “F0: Read DTC Infor As Stored By ECU” in
“F0: Diagnostic Trouble Codes”.
Is the DTC P0560 (Symptom Code 1) stored as
“Present Failure”?—Go to Step 3Refer to
Diagnostic Aids
and Go to Step
3
3 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Select “F1: Clear DTC Information” in “F0:
Diagnostic Trouble Codes” with the Tech 2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F0: Read
DTC Infor As Stored By ECU” in the “F0:
Diagnostic Trouble Codes”.
Was the DTC P0560 (Symptom Code 1) stored in this
ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 Was the battery jump start cable incorrectly
connecting?—Verify
procedure Go to Step 5
5 1. Using the Tech 2, ignition “On” and engine “On”.
2. Monitor the “System Voltage” in the data display.
3. Load the electrical system by turning on the
headlights, etc..
Does the Tech 2 indicate correct ignition voltage? 10 - 14.5V Go to Step 6Check the
charging
system
6 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 7

6E –256 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0560 (Symptom Code 2) (Flash Code 35)
System Voltage Too Low
Step Action Value(s) Yes No
1Was the “On-Board Diagnostic (OBD) System Check ”
performed?
— Go to Step 2 Go to
On Board
Diagnostic
(OBD) System Check
2 1. Connect the Tech 2. 2. Review and record the failure information.
3. Select “F0: Read DTC Infor As Stored By ECU ” in
“ F0: Diagnostic Trouble Codes ”.
Is the DTC P0560 (Symptom Code 2) stored as
“ Present Failure ”? —Go to Step 3 Refer to
Diagnostic Aids and Go to Step
3
3 1. Using the Tech 2, ignition “On ” and engine “Off ”.
2. Select “F1: Clear DTC Information ” in “F0:
Diagnostic Trouble Codes ” with the Tech 2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F0: Read
DTC Infor As Stored By ECU ” in the “F0:
Diagnostic Trouble Codes ”.
Was the DTC P0560 (Symptom Code 2) stored in this
ignition cycle? —Go to Step 4 Refer to
Diagnostic Aids and Go to Step
4
4 1. Using the Tech 2, ignition “On ” and engine “On ”.
2. Monitor the “System Voltage ” in the data display.
3. Load the electrical system by turning on the headlights, etc..
Does the Tech 2 indicate enough ignition voltage? 10 - 14.5V Go to Step 6Go to Step 5
5 Using the DVM and check the battery voltage at the battery terminal.
Does the tester indicate enough battery voltage?
10 - 14.5V Go to Step 6 Check the
charging
system, charge or replace the battery
6 Check for poor/faulty connection at the ECM connector. If a poor/faulty connection is found, repair
as necessary.
Was the problem found?
— Verify repair Go to Step 7
3
2 1
56C-56

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–361
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 check engine
lamp (MIL=malfunction indicator 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. Check thoroughly for any type of leak or
restriction.
Air intake ducts for collapsed or damaged areas.
Air leaks at throttle body mounting area, mass air flow
(MAF) sensor and intake manifold sealing surfaces.
Wiring for proper connections, pinches and cuts.
INTERMITTENT
Important: An intermittent problem may or may not turn
on the check engine lamp (MIL=malfunction indicator
lamp) 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.
Check engine lamp (MIL=malfunction indicator 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 have several features that can be used to
located an intermittent condition. Use the following
features to find intermittent faults:
To check for loss of diagnostic code memory,
disconnect the MAF sensor and idle the engine until the
check engine lamp (MIL=malfunction indicator lamp)
comes on. Diagnostic Trouble Code P0100 should be
stored and kept in memory when the ignition is turned
OFF.
If not, the ECM is faulty. When this test is completed,
make sure that you clear the Diagnostic Trouble Code
P0100 from memory.
An intermittent check engine lamp (MIL=malfunction
indicator lamp) with no stored Diagnostic Trouble Code
may be caused by the following:
Check engine lamp (MIL=malfunction indicator 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.
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.

6A-4 ENGINE MECHANICAL (6VE1 3.5L)
Engine Diagnosis
Hard Starting
1. Starting Motor Does Not Turn Over
Troubleshooting Procedure
Turn on headlights and starter switch.


Symptom Possible Cause Action
Headlights go out or dim considerably Battery run down or under charged Recharge or replace battery
Terminals poorly connected Clean battery posts and terminals
and connect properly
Starting motor coil circuit shorted Overhaul or replace
Starting motor defective Overhaul or replace

2. Ignition Trouble




Starting Motor Turns Over But
Engine Does Not Start Spark Test
Disconnect an ignition coil from any spark plug.
Connect the spark plug tester 5884003830, start the
engine, and check if a spark is generated in the spark
plug tester. Before starting the engine, make sure that
the spark plug tester is properly grounded. To avoid
electrical shock, do not touch the part where insulation
of the ignition coil is broken while the engine is running.


Symptom Possible Cause Action
Spark jumps across gap Spark plug defective Clean or replace
Ignition timing incorrect Refer to Ignition System
Fuel not reaching fuel injector(s) or
engine Refer to item 3 (Trouble in fuel
system)
Valve timing incorrect Adjust
Engine lacks compression Refer to item 4 (Engine lacks
compression)
No sparking takes place Ignition coil disconnected or broken Connect properly or replace
Electronic Ignition System with
module Replace
Poor connections in engine harness Correct
Engine Control Module cable
disconnected or defective Correct or replace