Throttle Position Sensor ISUZU TF SERIES 2004 Owners Manual

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-353
Step Action Value (s) Yes No
7
Remove the MAF & IAT sensor assembly and check for the
following conditions.

Objects blocking the air cleaner.

Objects blocking the MAF 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 Refer to DTC
P0101 and Go
to Step 8
8
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" from 0%
to 100% depending on accelerator pedal operation?

- Go to Step 10Go to Step 9
9
1. Using the Tech 2, ignition "On" and engine "Off".
2. Monitor the "Throttle Position" in the data display.
3. Adjust the accelerator cable or TPS within 0% to 100%.
Is the action complete?
- Verify repair -
10
Check for the following conditions.

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 11
11
Check the fuel control Heated Oxygen 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 exhaust signal which causes the
ECM to command and excessively lean air/fuel mixture.
Was a problem found?
- Verify repair Go to Step 12
12
Check the fuel pressure. Refer to 6E-116 Fuel System
Diagnosis.
Was a problem found?
- Verify repair Go to Step 13
13
Monitor "B1S1 (Bank 1 Sensor 1) Status" and "B2S1 (Bank 2
Sensor 1) Status" on the Tech 2.
Is the "B1S1 (Bank 1 Sensor 1) Status" or "B2S1 (Bank 2
Sensor 1) Status" in the rich condition?
- Go to Step 14Go to Step 15
14
Check items that can cause the engine to run rich. Refer to
DTC P0172 "O2 Sensor System Too Rich (Bank 1)" or DTC
P0175 "O2 Sensor System Too Rich (Bank 2)".
Was a problem found?
- Verify repair Go to Step 16

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-357
Step Action Value (s) Yes No
7
1. Using the Tech 2, ignition "On" and engine "On".
2. Monitor the "Mass Air Flow" in the data display.
Does the Tech 2 indicate correct "Mass Air Flow" as
shown in the following graph, when engine speed is
increasing little by little?




Characteris tic of MAF Sens or -Ref erence (No Engine Load)-
0 5 10 15 20 25 30 35 40 45 50
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Eng i ne Speed ( r pm) ( T ech2 R eadi ng )
Mass Air Flow (g/s)
( T ec h2 R eadi ng)

- Go to Step 9 Go to Step 8
8
Remove the MAF & IAT sensor assembly and check
for the following conditions.

Objects blocking the air cleaner.

Objects blocking the MAF 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 Refer to DTC
P0101 and Go to
Step 9
9
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"
from 0% to 100% depending on accelerator pedal
operation?




- Go to Step 11 Go to Step 10
10
1. Using the Tech 2, ignition "On" and engine "Off".
2. Monitor the "Throttle Position" in the data display.
3. Adjust the accelerator cable or TPS within 0% to
100%.
Is the action complete?
- Verify repair -
11
Check the fuel control Heated Oxygen 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 exhaust signal which causes the ECM to
command and excessively lean air/fuel mixture.
Was a problem found?
- Verify repair Go to Step 12

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-363
Step Action Value (s) Yes No
14
Check the EVAP purge solenoid valve operation.
Is the valve operated normally?
- Verify repair &
Go to Step 17 Verify repair &
Go to Step 15
15
Check the exhaust system for a possible restriction:

Damaged or collapsed pipes.

Internal catalytic converter failure.
Was a problem found?
- Verify repair &
Go to Step 17 Go to Step 16
16
1. Remove excessive carbon buildup with a top
engine cleaner. Refer to the instructions on the top
engine cleaner can.
2. Perform the exhaust emission test.
Does the vehicle pass the test?
- System OK Go to Step 18
17
Perform the exhaust emission test.
Does the vehicle pass the test?
- System OK Go to Step 18
18
Check the fuel control Heated Oxygen 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 exhaust signal which causes the ECM to
command and excessively lean air/fuel mixture.
Was a problem found?
- Verify repair Go to Step 19
19
Monitor "B1S1 (Bank 1 Sensor 1) Status" and "B2S1
(Bank 2 Sensor 1) Status" on the Tech 2.
Is the "B1S1 (Bank 1 Sensor 1) Status" or "B2S1
(Bank 2 Sensor 1) Status" in the rich condition?
- Go to Step 20 Go to Step 21
20
Check items that can cause the engine to run rich.
Refer to DTC P0172 "O2 Sensor System Too Rich
(Bank 1)" or DTC P0175 "O2 Sensor System Too Rich
(Bank 2)".
Was a problem found?
- Verify repair Go to Step 22
21
Check items that can cause the engine to run lean.
Refer to DTC P0171 "O2 Sensor System Too Lean
(Bank 1)" or DTC P0174 "O2 Sensor System Tool
Lean (Bank 2)".
Was a problem found?
- Verify repair 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

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-371
THROTTLE POSITION SENSOR
(TPS)

Location
Installed on the throttle body.

Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect the TPS connector.
3. Loosen two screws and remove TPS from the
throttle body.




Installation Procedure
1. Temporary tighten the TPS by two screws.
2. Connect a TPS connectors to the TPS.
3. Connect the Tech2 to the vehicle.
4. Connect the negative battery cable.
5. Select "Data Display" with the Tech2.
6. Check the throttle position data and adjust the TPS
position.
7. Tighten two screws.

NOTE:
Verify any DTCs (diagnosis Trouble Code) are not
stored after replacement.



IDLE AIR CONTROL (IAC) VALVE

Location
Installed on the throttle body.

Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect the IAC valve connector.
3. Loosen two screws and remove IAC valve from
the throttle body.




Cleaning and Inspection
1. Clean the IAC valve O-ring sealing surface, pintle
valve seat and air passage.
2. Use carburetor cleaner and a parts cleaning brush
to remove carbon deposit.
Do not use a cleaner that contain methyl ethyl
ketone. This is an extremely strong solvent and no
t
necessary for this type of deposit.
3. Shiny spots on the pintle are normal and do no
t
indicate misalignment or a bent pintle shaft.
4. Inspect the IAC valve O-ring for cuts, cracks o
r
distortion.

6-4 ENGINE DIAGNOSIS (C24SE)
Rough Engine Idling or Engine Stalling
Condition Possible cause Correction
Trouble in fuel injection system Idle air control valve defective Replace
Throttle shutting off incomplete Correct or replace
Throttle position sensor circuit
open or shorted Correct or replace
Fuel injector circuits open or
shorted Correct or replace
Fuel injectors damaged Replace
Fuel pump relay defective Replace
Manifold Absolute Pressure
Sensor cable disconnected or
broken Correct or replace
Manifold Absolute Pressure
Sensor defective Replace
Engine Coolant Temperature
Sensor cable disconnected or
broken Correct or replace
Engine Coolant Temperature
Sensor defective Replace
Intake Air Temperature sensor
cable disconnected or broken Correct or replace
Intake Air Temperature sensor
defective Replace
Knock Sensor (KS) circuits open
or shorted Correct or replace
KS defective Replace
KS Module circuits open or
ground Correct or replace
KS Module defective Replace
Vehicle Speed Sensor circuit open
or shorted Correct or replace
Vehicle Speed Sensor defective Replace
Trouble in emission control
system Engine Control Module defective Replace
Canister purge solenoid circuit
open Correct
Canister purge solenoid defective Replace
Evaporative Emission Canister
Purge control valve defective Replace
Trouble in ignition system Refer to Hard Start
Troubleshooting Guide
Others Engine lacks compression Refer to Hard Start
Troubleshooting Guide
Valve incorrectly seated Lap valve
Air Cleaner Filter clogged Replace filter element
Valve timing incorrect Readjust
Idle air control valve broken Replace

ENGINE DIAGNOSIS (C24SE) 6-5
Rough Engine Running
Condition Possible cause Correction
Engine misfires regularly Ignition coil layer shorted Replace
Spark plugs fouling Clean or install hotter type plug
Spark plug(s) insulator nose
leaking Replace
Spark plug wire incorrect Connect properly or replace
Fuel injector(s) defective Replace
Engine control module faulty Replace
Engine knocks regularly Spark plugs running too hot Install colder type spark plugs
Powertrain control module faulty Replace
Engine lacks power Spark plugs fouled Clean
Spark plug wire incorrect Connect properly or replace
Fuel injectors defective Replace
Manifold Absolute Pressure
(MAP)
Sensor or Manifold Absolute
Pressure Sensor circuit defective Correct or replace
Engine Coolant Temperature
Sensor or Engine Coolant
Temperature Sensor circuit
defective Correct or replace
Engine Control Module faulty Replace
Intake Air Temperature Sensor or
Intake Air Temperature Sensor
circuit defective Correct or replace
Throttle Position Sensor or
Throttle Position Sensor circuit
defective Correct or replace
Knock Sensor or Knock Sensor
circuits defective Correct or replace
Knock Sensor Module or Knock
Sensor Module circuits defective Correct or replace

6-6 ENGINE DIAGNOSIS (C24SE)
Hesitation
Condition Possible cause Correction
Hesitation on acceleration Throttle Position Sensor
adjustment incorrect Replace throttle valve assembly
Throttle Position Sensor circuit
open or shorted Correct or replace
Excessive play in accelerator
linkage Adjust or replace
Manifold Absolute Pressure
(MAP) Sensor circuit open or
shorted Correct or replace
MAP Sensor defective Replace
Intake Air Temperature (IAT)
Sensor circuit open or shorted Correct or replace
Knock Sensor (KS) Circuit open or
shorted Correct or replace
KS defective Replace
KS Module circuits open or
shorted Correct or replace
KS Module defective Replace
IAT Sensor defective Replace
Hesitation at high speeds
(Fuel pressure too low) Fuel tank strainer clogged Clean or replace
Fuel pipe clogged Clean or replace
Fuel filter clogged Replace
Defective fuel pump system Check and replace
Fuel Pressure Control Valve
leaking Replace
Hesitation at high speeds
(Fuel injector not working
normally) Power supply or ground circuit for
Multiport Fuel Injection System
shorted or open Check and correct or replace
Cable of Multiport Fuel Injection
System disconnected or defective Correct or replace
Hesitation at high speeds Engine Control Module defective Replace
Throttle Position Sensor circuit
open or shorted Correct or replace
Throttle Position Sensor defective Replace
Engine Coolant Temperature
Sensor circuit open or shorted Correct or replace
Engine Coolant Temperature
Sensor defective Replace
MAP Sensor cable open or
shorted Correct or replace
MAP Sensor defective Replace
IAT Sensor circuit open or shorted Correct or replace
IAT Sensor defective Replace
KS Circuit open or shorted Correct or replace
KS defective Replace
KS Module circuit open or shorted Correct or replace
KS Module defective Replace
Throttle valve not wide opened Check and correct or replace
Air Cleaner Filter clogged Replace filter element
Power supply voltage too low Check and correct or replace

ENGINE DIAGNOSIS (C24SE) 6-7
Engine Lacks Power
Condition Possible cause Correction
Trouble in fuel system Fuel Pressure Control Valve not
working normally Replace
Fuel injector clogged Clean or replace
Fuel pipe clogged Clean
Fuel filter clogged or fouled Replace
Fuel pump drive circuit not
working normally Correct or replace
Fuel tank not sufficiently breathing
due to clogged Evaporative
Emission Control System circuit Clean or replace
Water in fuel system Clean
Inferior quality fuel in fuel system Use fuel of specified octane rating
Engine Control Module supplied
poor voltage Correct circuit
Throttle Position Sensor cable
disconnected or broken Correct or replace
Throttle Position Sensor defective Replace
Manifold Absolute Pressure
Sensor not working normally Replace
Intake Air Temperature sensor not
working normally Replace
Engine Coolant Temperature
Sensor circuit open or shorted Correct or replace
Engine Coolant Temperature
Sensor defective Replace
Engine Control Module defective Replace
Trouble in intake or exhaust
system Air Cleaner Filter clogged Replace filter element
Air duct kicked or flattened Correct or replace
Ignition failure
- Refer to Hard Start
Troubleshooting Guide
Heat range of spark plug
inadequate Install spark plugs of adequate
heat range
Electronic Ignition System with
module Replace

6-8 ENGINE DIAGNOSIS (C24SE)
Condition Possible cause Correction
Engine overheating Level of Engine Coolant too low Replenish
Thermo switch or fan motor
defective Replace
Thermostat defective Replace
Engine Coolant pump defective Correct or replace
Radiator clogged Clean or replace
Radiator filter cap defective Replace
Level of oil in engine crankcase
too low or wrong oil in engine Change or replenish
Resistance in exhaust system
increased Clean exhaust system or replace
defective parts
Throttle Position Sensor
adjustment incorrect Adjust Wide Open Throttle switch
setting
Throttle Position Sensor circuit
open or shorted Correct or replace
Cylinder head gasket damaged Replace
Cooling Fan clutch defective Replace
Fan belt slipping Adjust tension of V-belt or replace
V-belt
Engine overcooling Thermostat defective Replace (Use a thermostat set to
open at 92
C (197.6
F))
Engine lacks compression - Refer to Hard Start
Others Tire inflation pressure abnormal Adjust to recommend pressures
Brake drag Adjust
Clutch slipping Adjust or replace
Level of oil in engine crankcase
too high Correct level of engine oil

Engine Noisy
Abnormal engine noise often consists of various
noises originating in rotating parts, sliding parts and
other moving parts of the engine. It is, therefore,
advisable to locate the source of noise systematically.

Condition Possible cause Correction
Noise from crank journals or from
crank bearings
(Faulty crank journals and crank
bearings usually make dull noise
that becomes more evident when
accelerating) Oil clearance increased due to
worn crank journals or crank
bearings Replace crank bearings and
crankshaft or regrind crankshaft
and install the over size bearing
Crankshaft out of round Replace crank bearings and
crankshaft or regrind crankshaft
and install the over size bearing
Crank bearing seized Replace crank bearings and
crankshaft or regrind crankshaft
and install the over size bearing

ENGINE DIAGNOSIS (C24SE) 6-11
Abnormal Combustion
Condition Possible cause Correction
Trouble in fuel injection system Fuel pressure control valve
defective Replace
Fuel filter clogged Replace
Fuel pump clogged Clean or replace
Fuel tank or fuel pipe clogged Clean or replace
Fuel injector clogged Clean or replace
Fuel pump relay defective Replace
Power supply cable for fuel pump
loosely connected or defective Reconnect, correct or replace
Manifold Absolute Pressure
Sensor circuit open or shorted Correct or replace
Manifold Absolute Pressure
Sensor defective Replace
Engine Coolant Temperature
(ECT) Sensor circuit open or
shorted Correct or replace
ECT Sensor defective Replace
Throttle Position Sensor
adjustment incorrect Reconnect
Throttle Position Sensor defective Replace
Throttle Position Sensor
connector loosely connected Reconnect
Vehicle Speed Sensor cable
loosely connected or defective Correct or replace
Vehicle Speed Sensor loosely
fixed Fix tightly
Vehicle Speed Sensor in wrong
contact or defective Replace
Engine Control Module cable
loosely connected or defective Correct or replace
Trouble in emission control
system Heated Oxygen Sensor circuit
open (If applicable) Correct or replace
Heated Oxygen Sensor defective
(If applicable) Replace
Signal vacuum hose loosely fitted
or defective Correct or replace
ECT Sensor circuit open or
shorted Correct or replace
ECT Sensor defective Replace
Evaporative Emission Control
system (If applicable) Refer to Section 6E
Trouble in ignition system - Refer to "Engine Lacks Power"
Trouble in cylinder head parts Carbon deposits in combustion
chamber Remove carbon
Carbon deposit on valve, valve
seat and valve guide Remove carbon