check engine ISUZU TF SERIES 2004 Workshop Manual

6E–250 ENGINE DRIVEABILITY AND EMISSIONS
19 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 20
20 1. Check for faulty engine mounts.
2. If a problem is found, repair as necessary.
Was a problem found?—Verify repair Go to Step 21
21 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 22
22 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 23
23 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–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

6E–252 ENGINE DRIVEABILITY AND EMISSIONS
12 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 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 for proper ignition voltage output with a spark
tester.
Was the problem found?—Verify repair Go to Step 16
16 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 17
17 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 suspencion of alcohol contamination,
completely drain the fuel, replace by fuel from known
vehicle source.—Verify repair Go to Step 18
18 Check the ex haust system for a possible restriction:
Damaged or collapsed pipes
Internal muffler failure
Was a problem found?—Verify repair Go to Step 19
19 Check for the following engine mechanical problems
(refer to Engine Mechanical):
Low compression
Leaking cylinder head gaskets
Worn camshaft
Loose timing belt
Was a problem found?—Verify repair Go to Step 20
20 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 21 Step Action Value(s) Yes No

6E–254 ENGINE DRIVEABILITY AND EMISSIONS
DETONATION/SPARK KNOCK SYMPTOM
DEFINITIONS: A mild to severe ping, usually worse under acceleration. The engine makes a sharp metallic knocking
sound that changes with throttle opening. Prolonged detonation may lead to complete engine tailure.
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. If Tech 2 readings are normal (refer to Typical
Scan Data Values) and there are no engine
mechanical faults, fill the fuel tank with a known
quality gasoline.
2. Re-evaluate the vehicle performance.
Is detonation present?—Go to Step 5Verify repair
5 1. Check for obvious overheating problems:
Low engine coolant
Restricted air flow to radiator
Incorrect coolant solution
2. If a problem is found, repair as necessary.
Was a problem found?—Verify repair Go to Step 6
6 Check the fuel pressure. Refer to 6E-108 page “Fuel
System Diagnosis” .
Was a problem found?—Verify repair Go to Step 7
7 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 8
8 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 9
9 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 10Refer to
Diagnostic
Trouble Code
P0123 for
further
diagnosis
10 Check the knock sensor wire, shield wire, or
installation condition.
Was a problem found?—Verify repair Go to Step 11
11 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 12

ENGINE DRIVEABILITY AND EMISSIONS 6E–255
12 Check spark plugs for proper heat range.
Were incorrect spark plugs installed?—Verify repair Go to Step 13
13 1. Remove ex cessive carbon buildup with a top
engine cleaner.
2. Re-evaluate vehicle performance.
Is detonation still present?—Verify repair Go to Step 14
14 Check for an engine mechanical problem. Perform a
cylinder compression check. Refer to Engine
Mechanical.
Was a problem found?—Verify repair Go to Step 15
15 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 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.—Verify Repair— Step Action Value(s) Yes No

6E–256 ENGINE DRIVEABILITY AND EMISSIONS
POOR FUEL ECONOMY SYMPTOM
DEFINITIONS: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, economy
is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.
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 owner’s driving habits.
Is the A/C On full time (defroster mode On)?
Are tires at the correct pressure?
Are ex cessively heavy loads being carried?
Is acceleration too much, too often?—Go to Step 5Go to Step 6
5 Review the items in Step 4 with the customer and
advise as necessary.
Is the action complete?—System OK—
6 Visually/physically check: Vacuum hoses for splits,
kinks, and improper connections and routing as
shown on the “Emission Control System Schematics”.
Was a problem found?—Verify repair Go to Step 7
7 Check for low engine coolant level.
Was a problem found? —Verify repair Go to Step 8
8 Check for incorrect or faulty engine thermostat. Refer
to Engine Cooling.
Was a problem found?—Verify repair Go to Step 9
9 Remove and check the air filter element for dirt or for
restrictions.
Was a problem found?—Verify repair Go to Step 10
10 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 11
11 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 12
12 Check the knock sensor wire, shield wire, or
installation condition.
Was a problem found?—Verify repair Go to Step 13
13 Check the fuel pressure. Refer to 6E-108 page
Fuel
System Diagnosis
.
Was a problem found?—Verify repair Go to Step 14

ENGINE DRIVEABILITY AND EMISSIONS 6E–257
14 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 15
15 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 16
16 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 17
17 Check for proper calibration of the speedometer.
Does the speed indicated on the speed meter closely
match the vehicle speed displayed on the Tech 2?—Go to Step 19Go to Step 18
18 Diagnose and repair the inaccurate speedometer
condition as necessary. Refer to Vehicle Speed
Sensor in Electrical Diagnosis.—Verify Repair—
19 Check for proper calibration of the fuel gauge.
Was a problem found?—Verify repair Go to Step 20
20 Check for the following engine mechanical problems
(refer to Engine Mechanical):
Low compression
Worn camshaft
Sticking or leaking valves
Valve timing
Was a problem found?—Verify repair Go to Step 21
21 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 22
22 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 23
23 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–258 ENGINE DRIVEABILITY AND EMISSIONS
EXCESSIVE EXHAUST EMISSIONS OR ODORS SYMPTOM
DEFINITIONS: Vehicle fails an emission test. There is ex cessive “rotten egg” smell. (Ex cessive odors do not
necessarily indicate ex cessive emissions.)
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 Does the customer continual accelerate On/Off during
cold condition?—System OK Go to Step 5
5 Is the customer using the incorrect fuel type?
—Replace with
unleaded fuel Go to Step 6
6 Check for vacuum leaks (vacuum lines, intake
manifold, throttle body, etc.)
Were any vacuum leaks found?—Go to Step 17Go to Step 7
7 1. Check fuel cap for proper installation.
2. Secure the fuel cap if necessary.
Was a problem found?—Go to Step 17Go to Step 8
8 Check the fuel pressure. Refer to 6E-108 page “Fuel
System Diagnosis” .
Was a problem found?—Go to Step 17Go to Step 9
9 1. Check for faulty, plugged or incorrectly installed
PCV valve.
2. Verify that the PCV system is not plugged.
Was a problem found? —Go to Step 17Go to Step 10
10 Check the injector connectors, if any of the injectors
are connected to an incorrect cylinder, correct as
necessary.
Was a problem found?—Go to Step 17Go to Step 11
11 Perform the
Injector Coil/Balance Test
(Refer to 6E-
98 page).
Was a problem found.—Go to Step 17Go to Step 12
12 Check for a problem with the engine cooling system.
Was a problem found?—Go to Step 17Go to Step 13
13 Check EVAP canister for fuel loading. Refer to
Evaporative Emission Control System.
Was a problem found?—Go to Step 17Go to Step 14
14 Check the EVAP purge solenoid valve operation.
Is the valve operated normally?—Go to Step 17Veri fy repai r &
Go to Step 15
15 Check the ex haust system for a possible restriction:
Damaged or collapsed pipes
Internal catalytic converter failure
Was a problem found?—Verify repair &
Go to Step 16Go to Step 17

ENGINE DRIVEABILITY AND EMISSIONS 6E–259
16 1. Remove ex cessive carbon buildup with a top
engine cleaner. Refer to the instructions on the top
engine cleaner can.
2. Perform the ex haust emission test.
Does the vehicle pass the test? —System OK Go to Step 18
17 Perform the ex haust emission test.
Does the vehicle pass the test?—System OK Go to Step 18
18 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 19
19 Monitor “B1S1 (Bank 1 Sensor 1) Status” on the Tech
2.
Is the “B1S1 (Bank 1 Sensor 1) Status” in the rich
condition?—Go to Step 20Go to Step 21
20 1. Check items that can cause the engine to run rich.
Refer to Diagnostic Aids in DTC P1167 “Fuel
Supply System Rich During Deceleration Fuel Cut
Off”. Make any necessary repairs.
2. Perform the ex haust emission test.
Does the vehicle pass the test? —System OK Go to Step 22
21 1. Check items that can cause the engine to run
lean. Refer to Diagnostic Aids in DTC P1171 “Fuel
Supply System Lean During Power Enrichment”.
Make any necessary repairs.
2. Perform the ex haust emission test.
Does the vehicle pass the test?—System OK Go to Step 22
22 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
Was a problem found?—Verify repair Go to Step 23
23 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 24 Step Action Value(s) Yes No

ENGINE DRIVEABILITY AND EMISSIONS 6E–261
DIESELING, RUN-ON SYMPTOM
DEFINITIONS: Engine continues to run after key is turned OFF, but runs very rough. If engine runs smoothly, check
the ignition switch and adjustment.
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 for a short between battery voltage and the
ignition feed circuit.
Was a problem found?—Verify repair Go to Step 5
5 Check the fuel leaking from injector. Refer to Fuel
System Diagnostic.
Was the problem found?—Verify repair Go to Step 6
6 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 7
7 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 8
8 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—