fuel pressure ISUZU TF SERIES 2004 Workshop Manual

ENGINE DRIVEABILITY AND EMISSIONS 6E–213
8 1. Using the Tech 2, ignition “On” and engine “On”.
2. Select the “Miscellaneous Test” and perform the
“IAC Control” in the “IAC System”.
3. Operate the Tech 2 in accordance with procedure.
Was the engine speed changed, when the IAC valve
is operating step by step?—Go to Step 10Go to Step 9
9 Check for the following conditions.
Objects blocking the IAC valve.
Objects blocking the throttle valve.
Vacuum leaking at throttle body.
If a problem is found, repair as necessary.
Was the problem found?—Verify repair Go to Step 14
10 Check for injector for the affected bank.
Refer to “Injector Coil Test & Injector Balance Test
Procedure” 6E-98 page.
Was the injector operation correct?
—Go to Step 11Refer to Injector
Coil Test &
Injector
Balance Test
Procedure
11 Check for fuel pressure.
Refer to “Fuel System Diagnosis” 6E-108 page.
Was the fuel pressure correct? —Go to Step 15Refer to Fuel
System
Diagnosis
12 Replace the TPS.
Is the action complete?—Veri fy repai r—
13 Replace the MAP sensor.
Is the action complete?—Veri fy repai r—
14 Replace the IAC valve.
Is the action complete?—Veri fy repai r—
15 Replace the O
2 sensor.
Was the problem solved?—Verify repair Go to Step 16
16 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 17
17 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 A ction Value(s) Yes No

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–216 ENGINE DRIVEABILITY AND EMISSIONS
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
8 1. Using the Tech 2, ignition “On” and engine “On”.
2. Select the “Miscellaneous Test” and perform the
“IAC Control” in the “IAC System”.
3. Operate the Tech 2 in accordance with procedure.
Was the engine speed changed, when the IAC valve
is operating step by step?—Go to Step 10Go to Step 9
9 Check for the following conditions.
Objects blocking the IAC valve.
Objects blocking the throttle valve.
Vacuum leaking at throttle body.
If a problem is found, repair as necessary.
Was the problem found?—Verify repair Go to Step 14
10 Check for injector for the affected bank.
Refer to “Injector Coil Test & Injector Balance Test
Procedure” 6E-98 page.
Was the injector operation correct?
—Go to Step 11Refer to Injector
Coil Test &
Injector
Balance Test
Procedure
11 Check for fuel pressure.
Refer to “Fuel System Diagnosis” 6E-108 page.
Was the fuel pressure correct? —Go to Step 15Refer to Fuel
System
Diagnosis
12 Replace the TPS.
Is the action complete?—Veri fy repai r—
13 Replace the MAP sensor.
Is the action complete?—Veri fy repai r—
14 Replace the IAC valve.
Is the action complete?—Veri fy repai r—
15 Replace the O
2 sensor.
Was the problem solved?—Verify repair Go to Step 16
16 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 17
17 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 A ction Value(s) Yes No

ENGINE DRIVEABILITY AND EMISSIONS 6E–235
22 Perform the procedure in Fuel System Pressure Test
(Refer to 6E-108
Fuel System Diagnosis) to
determine if there is a problem with fuel delivery.
Was a problem found?—Verify repair Go to Step 23
23 Refer to 6E-108 page
Fuel System Diagnosis to
determine if there is a problem with fuel delivery.
Was a problem found?—Verify repair Go to Step 24
24 Check for the following engine mechanical problems
(refer to Engine Mechanical):
Low compression
Leaking cylinder head gaskets
Worn camshaft
Camshaft drive belt slipped or stripped
Was a problem found?—Verify repair Go to Step 25
25 1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no
malfunctions have been found, review/inspect the
followi ng:
Visual/physical inspection
Te c h 2 d a t a
All electrical connections within a suspected
circuit and/or system
Was a problem found?—Verify repair Go to Step 26
26 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 27
27 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.—Verify Repair— Step Action Value(s) Yes No

6E–238 ENGINE DRIVEABILITY AND EMISSIONS
14 Drain sample fuel, visual inspection.
Any suspecion about the fuel, such as discoloration,
particle, contamination, water, unusual smell, then
drain the fuel from fuel tank.
Replace the fuel from know vehicle source.
If any suspicion of alcohol contamination, completely
drain the fuel, replace by fuel from known vehicle
source.—Verify repair Go to Step 15
15 Perform the procedure in Fuel System Pressure Test
(Refer to 6E-108
Fuel System Diagnosis) to
determine if there is a problem with fuel delivery.
Was a problem found?—Verify repair Go to Step 16
16 1. Check the injector connectors.
2. If any of the connectors are connected at an
improper cylinder, connect as necessary.
Was a problem found?—Verify repair Go to Step 17
17 Check for the following engine mechanical problems
(refer to Engine Mechanical):
Low compression
Leaking cylinder head gaskets
Worn camshaft
Camshaft drive belt slipped or stripped
Was a problem found?—Verify repair Go to Step 18
18 1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no
malfunctions have been found, review/inspect the
followi ng:
Visual/physical inspection
Te c h 2 d a t a
All electrical connections within a suspected
circuit and/or system
Was a problem found?—Verify repair Go to Step 19
19 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 20
20 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.—Verify Repair— Step Action Value(s) Yes No

ENGINE DRIVEABILITY AND EMISSIONS 6E–241
17 Perform the procedure in Fuel System Pressure Test
(Refer to 6E-108
Fuel System Diagnosis) to
determine if there is a problem with fuel delivery.
Was a problem found?—Verify repair Go to Step 18
18 Check for the following engine mechanical problems
(refer to Engine Mechanical):
Low compression
Leaking cylinder head gaskets
Worn camshaft
Sticking or leaking valves
Valve timing
Broken valve springs
Camshaft drive belt slipped or stripped
Was a problem found?—Verify repair Go to Step 19
19 1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no
malfunctions have been found, review/inspect the
followi ng:
Visual/physical inspection
Te c h 2 d a t a
All electrical connections within a suspected
circuit and/or system
Was a problem found?—Verify repair Go to Step 20
20 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 21
21 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.—Verify Repair— Step Action Value(s) Yes No

ENGINE DRIVEABILITY AND EMISSIONS 6E–243
9 Check the fuel pressure. Refer to 6E-108 page
Fuel
System Diagnosis
.
Was a problem found?—Verify repair Go to Step 10
10 Monitor “B1S1 (Bank 1 Sensor 1) Status” on the Tech
2.
Is the “B1S1 (Bank 1 Sensor 1) Status” in the rich
condition?—Verify repair Go to Step 11
11 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 12
12 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 13
13 Check for proper ignition voltage output with the spark
tester.
Was a problem found?—Verify repair Go to Step 14
14 Check for a loose ignition control module ground.
Was a problem found?—Verify repair Go to Step 15
15 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 16
16 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 17
17 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 18
18 1. Check the injector connectors.
2. If any of the connectors are connected at an
improper cylinder, connect as necessary.
Was a problem found?—Verify repair Go to Step 19
19 Check the ECM grounds to verify that they are clean
and tight. Refer to the ECM wiring diagrams.
Was a problem found?—Verify repair Go to Step 20
20 Visually/physically check the vacuum hose for splits,
kinks and proper connections and routing.
Was a problem found?—Verify repair Go to Step 21 Step Action Value(s) Yes No

ENGINE DRIVEABILITY AND EMISSIONS 6E–245
HESITATION, SAG, STUMBLE SYMPTOM
DEFINITIONS: Momentary lack of response as the
accelerator is pushed down. Can occur at any vehicle
speed. Usually most pronounced when first trying to
make the vehicle move, as from a stop sign. May cause
the engine to stall if severe enough.
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 Check the fuel quality.
Is the customer using improper fuel or degraded fuel?—Replace fuel 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.
Does the throttle position increase steady with
increasing smoothly?
—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 and excessively lean air/fuel mix ture.
Was a problem found?—Verify repair Go to Step 9
9 Check the fuel pressure. Refer to 6E-108
Fuel
System Diagnosis
.
Was a problem found?—Verify repair Go to Step 10

ENGINE DRIVEABILITY AND EMISSIONS 6E–249
10 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 11
11 Monitor “B1S1 (Bank 1 Sensor 1) Status” on the Tech
2.
Is the “B1S1 (Bank 1 Sensor 1) Status” in the lean
condition?—Go to Step 12Go to Step 13
12 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 13
13 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 14
14 Check the injector connectors, if any of the injectors
are connected an incorrect cylinder, correct as
necessary.
Was a problem found?—Verify repair Go to Step 15
15 Perform the “Injector Coil/Balance Test” (Refer to 6E-
98 page).
Was a problem found.—Verify repair Go to Step 16
16 1. Check for fuel in the pressure regulator vacuum
hose.
2. If fuel is present, replace the fuel pressure
regulator assembly.
Was a problem found?—Verify repair Go to Step 17
17 Check for proper ignition voltage output with the spark
tester.
Was a problem found?—Verify repair Go to Step 18
18 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 19 Step Action Value(s) Yes No

ENGINE DRIVEABILITY AND EMISSIONS 6E–251
LACK OF POWER, SLUGGISH OR SPONGY SYMPTOM
DEFINITIONS: Engine delivers less than ex pected power. Attempting part-throttle acceleration results in little or no
increase in vehicle speed.
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 1. Remove and check the air filter element for dirt or
restrictions.
2. Replace the air filter element if necessary.
Was a repair required?—Verify repair Go to Step 5
5 Check the ECM grounds to verify that they are clean
and tight. Refer to the ECM wiring diagrams.
Was a problem found?—Verify repair Go to Step 6
6 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 7
7 1. Using a Tech 2, display the ECT sensor and IAT
sensor value and warm up condition compared
with the typical data.
2. Check the specified value or wire.
Was the problem found?—Verify repair Go to Step 8
8 Observe the throttle position display on the Tech 2
while slowly increasing throttle pedal.
Does the throttle position increase steady with
increasing smoothly?
—Go to Step 9Refer to
Diagnostic
Trouble Code
P0123 for
further
diagnosis
9 Check the knock sensor wire, shield wire, or
installation condition.
Was a problem found?—Verify repair Go to Step 10
10 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 and excessively lean air/fuel mix ture.
Was a problem found?—Verify repair Go to Step 11
11 Check the fuel pressure. Refer to
Fuel System
Diagnosis
6E-108.
Was a problem found?—Verify repair Go to Step 12