2004 ISUZU TF SERIES display

6E–212 ENGINE DRIVEABILITY AND EMISSIONS
Perform “I njector Balance Test” - Refer to Fuel
System Diagnosis.
Check the EVAP canister for fuel saturation - If full of
fuel, check canister control and hoses. Refer to
Evaporative (EVAP) Emission Control System.
Check for a leak in the fuel pressure regulator
diaphragm by checking the vacuum line to toe
regulator for the presence of fuel.An intermittent TP sensor output will cause the
system to go rich due to a false indication of the
engine accelerating.
Silicon contamination of the HO2S can also cause a
high HO2S voltage to be indicated. This condition is
indicated by a powdery white deposit on the portion
of the HO2S ex posed to the ex haust stream. If
contamination is noticed, replace the affected HO2S.
Diagnostic Trouble Code (DTC) P1167
Fuel Supply Sy stem Rich During Deceleration Fuel Cutoff
Step A ction Value(s) Yes No
1 Was 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 By Priority” in “F0:
Diagnostic Trouble Code”.
Is the DTC P1167 stored as “Present Failure”?—Go to Step 3Refer 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 P1167 stored in this ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Monitor the “Throttle Position” in the data display.
Does the Tech 2 indicate correct “Throttle Position” in
accordance with accelerator pedal operation? —Go to Step 6Go to Step 5
5 Check for the following conditions.
Objects blocking the throttle valve.
Incorrectly installed.
If a problem is found, repair as necessary.
Was the problem found?—Verify repair Go to Step 12
6 1. Using the Tech 2, ignition “On” and engine “On”.
2. Monitor the “Manifold Absolute Pressure” in the
data display.
Does the Tech 2 indicate correct “Manifold Absolute
Pressure” in accordance with engine speed or
acceleration? —Go to Step 8Go to Step 7
7 Remove the MAP sensor and check for the following
conditions.
Objects blocking the air cleaner.
Objects blocking the MAP sensor.
Objects blocking the throttle valve.
Vacuum leaking at intake duct.
Vacuum leaking at throttle body.
If a problem is found, repair as necessary.
Was the problem found?—Verify repair Go to Step 13

ENGINE DRIVEABILITY AND EMISSIONS 6E–215
Diagnostic Aids
Check for the following conditions:
Heated oxygen sensor wiring - The sensor pigtail
may be routed incorrectly and contacting the ex haust
system.
Poor ECM to engine block ground.
Fuel pressure - The system will go lean if pressure is
too low. The ECM can compensate for some
decrease. However, if fuel pressure is too low, a
diagnostic Trouble Code P1171 may be set. Refer to
Fuel System Diagnosis.
Lean injector(s) - Perform “Injector Balance Test.”Vacuum leaks - Check for disconnected or damaged
vacuum hoses and for vacuum leaks at the intake
manifold, throttle body, and PCV system.
Ex haust leaks - An ex haust leak may cause outside
air to be pulled into the ex haust gas stream past the
HO2S, causing the system to appear lean. Check for
exhaust leaks that may cause a false lean condition
to be indicated.
Fuel contamination - Water, even in small amounts,
can be delivered to the fuel injectors. The water can
cause a lean ex haust to be indicated, Ex cessive
alcohol in the fuel can also cause this condition.
Refer to Fuel System Diagnosis for the procedure to
check for fuel contamination.
Diagnostic Trouble Code (DTC) P1171
Fuel Supply Sy stem Lean During Power Enrichment
Step A ction Value(s) Yes No
1 Was 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 By Priority” in “F0:
Diagnostic Trouble Code”.
Is the DTC P1171 stored as “Present Failure”?—Go to Step 3Refer 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 P1171 stored in this ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Monitor the “Throttle Position” in the data display.
Does the Tech 2 indicate correct “Throttle Position” in
accordance with accelerator pedal operation? —Go to Step 6Go to Step 5
5 Check for the following conditions.
Objects blocking the throttle valve.
Incorrectly installed.
If a problem is found, repair as necessary.
Was the problem found?—Verify repair Go to Step 12
6 1. Using the Tech 2, ignition “On” and engine “On”.
2. Monitor the “Manifold Absolute Pressure” in the
data display.
Does the Tech 2 indicate correct “Manifold Absolute
Pressure” in accordance with engine speed or
acceleration? —Go to Step 8Go to Step 7

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
follow ing:
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”
(ex ample 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 No
1Was the “On-Board Diagnostic (OBD) System Check”
performed?—Go to Step 2Go to OBD
System Check
2 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
3 Was a visually/physical check performed?
—Go to Step 4Go to Visual /
physical Check.
4 Check the “Ignition coil” fuse (15A) and “ECM” fuse
(15A).
Was a fuse blown?—Verify repair Go to Step 5
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 6Verify & repair
6 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
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
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
9 If oscilloscope is available, check the wave form of the
CKP signal.
Was the correct wave form found?—Go to Step 12Go to Step 10
10 Check the CKP sensor wire for open or short circuit.
Was a problem found?—Verify repair Go to Step 11
11 Replace CKP sensor.
Is there still problem?—Replace pulsar
ring. Verify repair

6E–236 ENGINE DRIVEABILITY AND EMISSIONS
HARD START SYMPTOM
DEFINITIONS: Engine cranks, but does not start for a long time. Does eventually start, of may start and then
immediately stall.
Step Action Value(s) Yes No
1Was the “On-Board Diagnostic (OBD) System Check”
performed?—Go to Step 2Go to OBD
System Check
2 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
3 Was a visually/physical check performed?
—Go to Step 4Go to Visual /
physical Check.
4 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 5
5 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 6
6 Check engine coolant temperature (ECT) sensor for
shift in value.
1. After 8 hours with hood up and the engine not
running, connect the Tech 2.
2. Ignition On, engine not running.
3. Using Tech 2, compare Engine Coolant
Temperature to Intake Air Temperature.
Are ECT and IAT within the specified value of each
other? 5°CGo to Step 8Go to Step 7

ENGINE DRIVEABILITY AND EMISSIONS 6E–237
7 1. Using a Tech 2, display the engine coolant
temperature and note the value.
2. Check the resistance of the engine coolant
temperature sensor.
Is the actual resistance near the resistance value in
the chart for the temperature that was noted?
—Go to Step 8Replace the
ECT sensor.
Verify repair
8 1. Using a Tech 2, display the MAP sensor value in
comparison with atmosphere temperature.
2. Check for a faulty, plugged, or incorrectly installed
MAP sensor.
Was the problem found?—Verify repair Go to Step 9
9 Visually/physically inspect all spark plug high-tension
cables. Check for the following conditions:
Verify that the resistance of all spark plug high-
tension cables are less than the specified value.
Verify that the all spark plug high-tension cables are
correctly fitted to eliminate cross-fitting.
Verify that the all spark plug high-tension cables are
not arcing to ground.
Spraying the spark plug high-tension cables with a
light mist of water may help locate an intermittent
problem.
Was a problem found?#1 cyl. 4.4k

#2 cyl. 3.6k

#3 cyl. 3.1k

#4 cyl. 2.8k
Verify repair Go to Step 10
10 Check for proper ignition voltage output with a spark
tester.
Was the problem found?—Verify repair Go to Step 11
11 1. Remove the spark plugs and check for gas or oil
fouling cracks, wear, improper gap, burned
electrodes, heavy deposits, or improper heat
range.
2. If spark plugs are fouled, the cause of fouling must
be determined before replacing the spark plugs.
Was a problem found?—Verify repair Go to Step 12
12 Check for a loose ignition control module ground.
Was a problem found?—Verify repair Go to Step 13
13 1. Check the ignition coil secondary resistance.
2. Replace the coil if it is greater than the specified
resistance.
Did the coil require replacement? 2.5k
Verify repair Go to Step 14 Step Action Value(s) Yes No
Temperature (°C) Resistance (
) (Approximately)
-20 26740
09120
20 3500
40 1464
60 664
80 333
100 175
120 102

6E–240 ENGINE DRIVEABILITY AND EMISSIONS
7 1. Using a Tech 2, display the engine coolant
temperature and note the value.
2. Check the resistance of the engine coolant
temperature sensor.
Is the actual resistance near the resistance value in
the chart for the temperature that was noted?
—Go to Step 8Replace the
ECT sensor.
Verify repair
8 1. Using a Tech 2, display the MAP sensor value in
comparison with atmosphere temperature.
2. Check for a faulty, plugged, or incorrectly installed
MAP sensor.
Was the problem found?—Verify repair Go to Step 9
9 Using Tech 2, monitor throttle position with the engine
idling.
Is the throttle position at the specified value and
steady?
0% Go to Step 10Refer to
Diagnostic
Trouble Code
P0123 for
further
diagnosis
10 Check for proper ignition voltage output with the spark
tester.
Was a problem found?—Verify repair Go to Step 11
11 1. Remove the spark plugs and check for gas or oil
fouling cracks, wear, improper gap, burned
electrodes, heavy deposits, or improper heat
range.
2. If spark plugs are fouled, the cause of fouling must
be determined before replacing the spark plugs.
Was a problem found?—Verify repair Go to Step 12
12 Check for a loose ignition control module ground.
Was a problem found?—Verify repair Go to Step 13
13 Check items that can cause the engine to run rich.
Refer to DTC P1167 “Fuel Supply System Rich During
Deceleration Fuel Cut Off”.
Was a problem found?—Verify repair Go to Step 14
14 Check items that can cause the engine to run lean.
Refer to DTC P1171 “Fuel Supply System Lean
During Power Enrichment”.
Was a problem found?—Verify repair Go to Step 15
15 Check the injector connectors, if any of the injectors
are connected any incorrect cylinder, correct as
necessary.
Was a problem found?—Verify repair Go to Step 16
16 1. Check for faulty engine mounts.
2. If a problem is found, repair as necessary.
Was a problem found?—Verify repair Go to Step 17 Step Action Value(s) Yes No
Temperature (°C) Re sista nce (
) (Appro x imately)
-20 26740
09120
20 3500
40 1464
60 664
80 333
100 175
120 102

6E–242 ENGINE DRIVEABILITY AND EMISSIONS
SURGES AND/OR CHUGS SYMPTOM
DEFINITIONS: See the illustration below. Feels like the
vehicle speeds up and slows down with no charge in the
accelerator pedal.
Step Action Value(s) Yes No
1Was the “On-Board Diagnostic (OBD) System Check”
performed?—Go to Step 2Go to OBD
System Check
2 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
3 Was a visual/physical check performed?
—Go to Step 4Go to Visual /
physical Check.
4 Be sure that the driver understands A/C compressor
operation as ex plained in the owner’s manual. Inform
the customer how the A/C clutch operate.
Is the customer ex periencing a normal condition?—System OK Go to Step 5
5 1. Using a Tech 2, display the MAP sensor value in
comparison with atmosphere temperature.
2. Check for a faulty, plugged, or incorrectly installed
MAP sensor.
Was the problem found?—Verify repair Go to Step 6
6 Observe the throttle position display on the Tech 2
while slowly increasing throttle pedal.
Is the throttle position at the specified value and
steady in any position?
—Go to Step 7Refer to
Diagnostic
Trouble Code
P0123 for
further
diagnosis
7 Check the knock sensor wire, shield wire, or
installation condition.
Was a problem found?—Verify repair Go to Step 8
8 Run Engine.
Check the fuel control Heated Ox ygen Sensor
(HO2S). When monitored on the Tech 2, the HO2S
should respond quickly to different throttle positions. If
it doesn’t check for silicon or other contaminates from
fuel or use of improper sealant. The sensors may
have a white powdery coating. Silicon contamination
sends a rich ex haust signal which causes the ECM to
command an ex cessively lean air/fuel mixture.
Was a problem found?—Verify repair Go to Step 9