2004 ISUZU TF SERIES instrument panel

6E –248 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0500 (Symptom Code B) (Flash Code 24)
Vehicle Speed Sensor Incorrect Signal
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 P0500 (Symptom Code B) 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 P0500 (Symptom Code B) stored in this
ignition cycle? —Go to Step 4 Refer to
Diagnostic Aids and Go to Step
4
4 Perform test drive and check the speed meter. Does the speed meter indicate correct vehicle speed. —Go to Step 5 Go to Step 6
5 Perform test drive and use the Tech 2. Monitor the “Vehicle Speed ” in the data display.
Does the Tech 2 indicate correct vehicle speed as
same as the speed meter indication in the instrument
panel? —Go to Step 17 Go to Step 7
6 Check for poor/faulty connection at the VSS, TCM (A/ T 2WD) and meter connectors. If a poor/faulty
connection is found, repair the faulty terminal.
Was the problem found?
— Verify repair Go to Step 8
13
2
9 10
10 B-24
C-94(10) E-44

6A-20 ENGINE MECHANICAL (6VE1 3.5L)
Malfunction Indicator Lamp
The instrument panel “CHECK ENGINE" Malfunction
Indicator Lamp (MIL) illuminates by self diagnostic
system when the system checks the starting of engine,
or senses malfunctions. ”CHECK ENGINE" MIL does
not illuminate at the starting of engine

Symptom Possible Cause Action
“CHECK ENGINE" MIL does not
illuminate at the starting of engine Bulb defective Replace
MIL circuit open Correct or replace
Command signal circuit to operate
self diagnostic system shorted Correct or replace
Engine Control Module (ECM) cable
loosely connected, disconnected or
defective Correct or replace
ECM defective Replace
“CHECK ENGINE" MIL illuminates,
and stays on Deterioration of heated oxygen
sensor internal element Replace
Heated oxygen sensor connector
terminal improper contact Reconnect properly
Heated oxygen sensor lead wire
shorted Correct
Heated oxygen sensor circuit open Correct or replace
Deterioration of engine coolant
temperature sensor internal element Replace
Engine coolant temperature sensor
connector terminal improper contact Reconnect properly
Engine coolant temperature sensor
lead wire shorted Correct
Engine coolant temperature sensor
circuit open Correct or replace
Throttle position sensor open or
shorted circuits Correct or replace
Deterioration of crankshaft position
sensor Replace
Crankshaft position sensor circuit
open or shorted Correct or replace
Vehicle speed sensor circuit open Correct or replace
Intake air temperature sensor circuit
open or shorted Correct or replace
Fuel injector circuit open or shorted Correct or replace
ECM driver transistor defective Replace ECM
Malfunctioning of ECM RAM
(Random Access Memory) or ROM
(Read Only Memory) Replace ECM

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-73
Intermittent Check Engine Lamp
In the case of an “intermittent" fault, the MIL (“Check
Engine" lamp) may illuminate and then (after three trips)
go “OFF". However, the corresponding diagnostic
trouble code will be stored in the memory. When
unexpected diagnostic trouble codes appear, check fo
r
an intermittent malfunction.
A diagnostic trouble code may reset. Consult the
“Diagnostic Aids" associated with the diagnostic trouble
code. A physical inspection of the applicable sub–
system most often will resolve the problem.
Data Link Connector (DLC)
The provision for communication with the control
module is the Data Link Connector (DLC). The DLC is
used to connect to a Tech 2. Some common uses o
f
the Tech 2 are listed below:

Identifying stored Diagnostic Trouble Codes (DTCs).

Clearing DTCs.

Performing out put control tests.

Reading serial data.








060RW046
Verifying Vehicle Repair
Verification of vehicle repair will be more
comprehensive for vehicles with OBD system
diagnostic. Following a repair, the technician should
perform the following steps:
1. Review and record the Fail Records and/or Freeze
Frame data for the DTC which has been diagnosed
(Freeze Frame data will only be stored for an A or B
type diagnostic and only if the MIL has been
requested).
2. Clear DTC(s).
3. Operate the vehicle within conditions noted in the
Fail Records and/or Freeze Frame data.
4. Monitor the DTC status information for the specific
DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.
Following these steps are very important in verifyin
g
repairs on OBD systems. Failure to follow these steps
could result in unnecessary repairs.
Reading Flash Diagnostic Trouble Codes
The provision for communicating with the Engine
Control Module (ECM) is the Data Link Connecto
r
(DLC). The DLC is located behind the lower front
instrument panel. It is used in the assembly plant to
receive information in checking that the engine is
operating properly before it leaves the plant.
The diagnostic trouble code(s) (DTCs) stored in the
ECM's memory can be read either through a hand-held
diagnostic scanner plugged into the DLC or by counting
the number of flashes of the Check Engine Lamp (MIL)
when the diagnostic test terminal of the DLC is
grounded. The DLC terminal “6" (diagnostic request) is
pulled “Low" (grounded) by jumpering to DLC terminal
“4", which is a ground wire.
This will signal the ECM that you want to “flash" DTC(s),
if any are present. Once terminals “4" and “6" have
been connected, the ignition switch must be moved to
the “ON" position, with the engine not running. At this
point, the “Check Engine" MIL should flash DTC12
three times consecutively.
This would be the following flash, sequence: "flash,
pause, flash?flash, long pause, flash, pause,
flash?flash, long pause, flash, pause, flash?flash". DTC
12 indicates that the ECM's diagnostic system is
operating. If DTC 12 is not indicated, a problem is
present within the diagnostic system itself, and should
be addressed by consulting the appropriate diagnostic
chart in DRIVEABILITY AND EMISSIONS.
Following the output of DTC 12, the “Check Engine" MIL
will indicate a DTC three times if a DTC is present, or i
t
will simply continue to output DTC12. If more than one
DTC three has been stored in the ECM's memory, the
DTC(s) will be output from the lowest to the highest,
with each DTC being displayed three times.
Reading Diagnostic Trouble Codes Using a
TECH 2
The procedure for reading diagnostic trouble code(s) is
to used a diagnostic Tech 2. When reading DTC(s),
follow instructions supplied by Tech 2 manufacturer.
For the 1998 model year, Isuzu dealer service
departments will continue to use Tech 2.

6E-74 3.5L ENGINE DRIVEABILITY AND EMISSIONS








0.4 Sec 0.4 Sec
.

ON

OFF




3.2 Sec.

1.2 Sec.



3.2 Sec.


0.4 Sec 0.4 Sec
.
ON

OFF


3.2 Sec.

1.2 Sec.


3.2 Sec.



Self-diagnosis Start

Normal Code (12)
Trouble Code (32)


121212141414323232

In case DTC 14 & 32 are stored

Clearing Diagnostic Trouble Codes
Important: Do not clear DTCs unless directed to do so
by the service information provided for each diagnostic
procedure. When DTCs are cleared, the Freeze Frame
and Failure Record data which may help diagnose an
intermittent fault will also be erased from memory.
If the fault that caused the DTC to be stored into
memory has been corrected, the Diagnostic Executive
will begin to count the “warm-up" cycles with no furthe
r
faults detected, the DTC will automatically be cleared
from the ECM memory.
To clear Diagnostic Trouble Codes (DTCs), use the
Tech 2 “clear DTCs" or “clear information" function.
When clearing DTCs follow instructions supplied by the
Tech 2 manufacturer.
When a Tech 2 is not available, DTCs can also be
cleared by disconnecting one of the following sources
for at least thirty (30) seconds.
To prevent system damage, the ignition key must be
“OFF" when disconnecting or reconnecting battery
power.

The power source to the control module. Examples:
fuse, pigtail at battery ECM connectors etc.

The negative battery cable. (Disconnecting the
negative battery cable will result in the loss of othe
r
on-board memory data, such as preset radio tuning).
On-Board Diagnosis (Self-Diagnosis)
1. The Engine Control Module (ECM) conducts a
self-test of most of the wiring and components in
the system each time the key is turned to ON, and
can detect faults in the system while the key is ON.
If a fault is detected, the ECM will store a trouble
code in memory and flash the CHECK ENGINE
indicator to alert the driver.
2. The Diagnostic Trouble Codes (DTC) can be
displayed by shorting together terminals and the
Data Link Connector (DLC) located belo
w
Instrument Panel of drivers side.
The CHECK ENGINE indicator will flash DTC 12
three times, followed by any DTC.If several DTC are
stored, each DTC will be displayed three times. The
DTC will be displayed in numerical order. The DTC
display will continue as long as the DLC is shorted.
Some DTC can cause other DTC to be stored, It is
important to diagnose and repair the lowes
t
numbered DTC first before going on to the highe
r
numbered DTC.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E -83

MISCELLANEOUS TEST
The state of each circuit can be tested by using
miscellaneous test menus. Especially when DTC cannot
be detected, a faulty circuit can be diagnosed by testing
each circuit by means of these menus.
Even DTC has been detected, the circuit tests using
these menus could help discriminate between a
mechanical trouble and an electrical trouble.
Connect Tech 2 and select "Powertrain", "3.5L V6 6VE1
Hitachi" & "Miscellaneous Test".

F0: Lamps
F0: Malfunction Indicator Lamp
When the Tech 2 is operated, "Malfunction Indicato
r
Lamp (Check Engine Lamp)" is turned on or off.
The circuit is normal if the "Malfunction Indicator Lamp
(Check Engine Lamp)" in the instrument panel is turned
on or off in accordance with this operation.

F1: Relays
F0: Fuel Pump Relay
When the Tech 2 is operated, fuel pump relay signal
turns ON or OFF.
The circuit is normal if fuel pump sound is generated in
accordance with this operation when key switch is
turned ON.

"F1: A/C Clutch Relay"
When the Tech 2 is operated, A/C clutch relay signal
turns ON or OFF.
The circuit is normal if A/C compressor clutch is
energized in accordance with this operation when the
engine is running.

F2: EVAP
F0: Purge Solenoid
When the Tech 2 is operated, duty ratio of EVAP purge
solenoid is changed 10%-by-10%.

Purge Solenoid
Engine Speed 800 RPM
Desired Idle Speed 762 RPM
Engine Coolant Temperature 80

C
Start Up ECT 50

C
Intake Air Temperature 30

C
Throttle Position 0 %
EVAP Purge Solenoid 10 %



Press "Increase" key.

Then, EVAP Purge Solenoid increases

10%-by-10%.


Press "Quit" Key.

F3: IAC System
F0: RPM Control
When the Tech 2 is operated, "Desired Idle Speed"
increases 50rpm-by-50rpm up to 1550rpm.
The circuit is normal if engine speed is changed in
accordance with this operation.
RPM Control
Engine Speed 850 RPM
Desired Idle Speed 850 RPM
Engine Coolant Temperature 80

C
Start Up ECT 50

C
Intake Air Temperature 30

C
Throttle Position 0 %
Desired Idle Speed 850 RPM



Press "Increase" key.

Then, Desired Idle speed increases

50rpm-by-50rpm up to 1550rpm. Engine speed is
also changed by this operation.


Press "Quit" Key.

F0: IAC Control
When the Tech 2 is operated, "Idle Air Control"
increases or decreases 10steps-by-10steps up to
160steps.
The circuit is normal if idle engine speed is changed in
accordance with this operation.
IAC Control
Engine Speed 875 RPM
Desired Idle Speed 762 RPM
Engine Coolant Temperature 80

Start Up ECT 50

Intake Air Temperature 30

Throttle Position 0 %
Idle Air Control 30 Steps



Press "Increase" key.

Then, Idle Air Control increases 10steps-by-
10steps up to 160steps.

Engine speed is also changed by this operation.


Press "Quit" Key.

6E-280 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0500 (Flash Code 24) Vehicle Speed Sensor
(VSS) Circuit Range/Performance

Step Action Value (s) Yes No
1
Was 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 By Priority" in "F0:
Diagnostic Trouble Code".
Is the DTC P0500 stored as "Present Failure"?
- Go to Step 3 Refer to
Diagnostic Aids
and Go to Step 3
3
1. Using the Tech2, ignition "On" and engine "Off".
2. Select "Clear DTC Information" with the Tech2 and
clear the DTC information.
3. Operate the vehicle and monitor the "F5: Failed This
Ignition" in "F2: DTC Information"
Was the DTC P0500 stored in this ignition cycle?
- Go to Step 4 Refer to
Diagnostic Aids
and Go to Step 4
4
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 5
5
Perform test drive and check the speed meter.
Does the speed meter indicate correct vehicle speed.
- Go to Step 6 Go to Step 7
6
Perform test drive and use the Tech 2.
Monitor the "Vehicle Speed" in the data display.
Does the Tech 2 indicate correct vehicle speed as
same as the speed meter indication in the instrument
panel?
- Go to Step 25 Go to Step 8
7
Check for poor/faulty connection at the VSS and meter
connectors. If a poor/faulty connection is found, repair
the faulty terminal.
Was the problem found?
B-24E-44







- Verify repair Go to Step 9

6-14 ENGINE DIAGNOSIS (C24SE)
Malfunction Indicator Lamp
The instrument panel "CHECK ENGINE" Malfunction
Indicator lamp (MIL) illuminates by self diagnostic
system when the system checks the starting of
engine, or senses malfunctions.

Condition Possible cause Correction
"CHECK ENGINE" MIL does not
illuminate at the starting of engine Bulb defective Replace
MIL circuit open Correct or replace
Command signal circuit to operate
self diagnostic system shorted Correct or replace
Engine Control Module (ECM)
cable loosely connected,
disconnected or defective Correct or replace
ECM defective Replace
“CHECK ENGINE” MIL
illuminates, and stays on Deterioration heated oxygen
sensor of internal element Replace
Heated oxygen sensor connector
terminal improper contact
(If applicable) Reconnect properly
Heated oxygen sensor lead wire
shorted (If applicable) Correct
Heated oxygen sensor circuit
open (If applicable) Correct or replace
Deterioration engine coolant
temperature sensor of internal
element Replace
Engine coolant temperature
sensor connector terminal
improper contact Reconnect properly
Engine coolant temperature
sensor lead wire shorted Correct
Engine coolant temperature
sensor circuit open Correct or replace
Throttle position sensor open or
shorted circuits Correct or replace
Deterioration of crankshaft
position sensor Replace
Crankshaft position sensor circuit
open or shorted Correct or replace
Vehicle speed sensor circuit open Correct or replace
Manifold absolute pressure sensor
circuit open or shorted Correct or replace
Intake air temperature sensor
circuit open or shorted Correct or replace
Fuel injector circuit open or shorted Correct or replace
ECM driver transistor defective Replace EPROM or ECM
Malfunctioning of ECM RAM
(Random Access Memory) or
Malfunctioning of ECM PROM
(Programmed Read Only Memory)Replace EPROM or ECM

6E–68 ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD)
On-Board Diagnostic Tests
A diagnostic test is a series of steps, the result of which
is a pass or fail reported to the diagnostic ex ecutive.
When a diagnostic test reports a pass result, the
diagnostic ex ecutive records the following data:
The diagnostic test has been completed since the
last ignition cycle.
The diagnostic test has passed during the current
ignition cycle.
The fault identified by the diagnostic test is not
currently active.
When a diagnostic test reports a fail result, the
diagnostic ex ecutive records the following data:
The diagnostic test has been completed since the
last ignition cycle.
The fault identified by the diagnostic test is currently
active.
The fault has been active during this ignition cycle.
The operating conditions at the time of the failure.
The Diagnostic Executive
The Diagnostic Executive is a unique segment of
software which is designed to coordinate and prioritize
the diagnostic procedures as well as define the protocol
for recording and displaying their results. The main
responsibilities of the Diagnostic Ex ecutive are listed as
follows:
Commanding the check engine lamp on and off
DTC logging and clearing
Current status information on each diagnostic
Diagnostic Information
The diagnostic charts and functional checks are
designed to locate a faulty circuit or component through
a process of logical decisions. The charts are prepared
with the requirement that the vehicle functioned
correctly at the time of assembly and that there are not
multiple faults present.
There is a continuous self-diagnosis on certain control
functions. This diagnostic capability is complemented
by the diagnostic procedures contained in this manual.
The language of communicating the source of the
malfunction is a system of diagnostic trouble codes.
When a malfunction is detected by the control module, a
diagnostic trouble code is set and the check engine
lamp is illumi nated.
Check Engine Lamp
The check engine lamp looks the same as the check
engine lamp you are already familiar with, the “Check
Engine” lamp.
Basically, the check engine lamp is turned on when the
ECM detects a DTC that will impact the vehicle
emissions.
When the check engine lamp remains “ON” while the
engine is running, or when a malfunction issuspected due to a driveability or emissions problem,
a Powertrain On-Board Diagnostic (OBD) System
Check must be performed. The procedures for these
checks are given in On-Board Diagnostic (OBD)
System Check. These checks will ex pose faults
which may not be detected if other diagnostics are
performed first.
Data Link Connector (DLC)
The provision for communication with the contorl
module is the Data Link Connector (DLC). It is located
behind the lower front instrument panel. The DLC is
used to connect to a Tech 2. Some common uses of the
Tech 2 are listed below:
Identifying stored Diagnostic Trouble Codes (DTCs).
Clearing DTCs.
Reading serial data.
Ver ify in g Veh icle Repair
Verification of vehicle repair will be more
comprehensive for vehicles with OBD system
diagnostic. Following a repair, the technician should
perform the following steps:
1. Review and record the Fail Records for the DTC
which has been diagnosed.
2. Clear DTC(s).
3. Operate the vehicle within conditions noted in the
Fail Records.
4. Monitor the DTC status information for the specific
DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.
Following these steps is very important in verifying
repairs on OBD systems. Failure to follow these steps
could result in unnecessary repairs.