2004 ISUZU TF SERIES coolant temperature

6A-6 ENGINE MECHANICAL (6VE1 3.5L)
Rough Engine Idling or Engine Stalling
Symptom Possible Cause Action
Trouble in fuel injection system Idle air control valve defective Replace
Throttle shutting off incomplete Replace
Throttle position sensor circuit open
or shorted Correct or replace
Fuel injector circuits open or shortedCorrect or replace
Fuel injectors damaged Replace
Fuel pump relay defective Replace
Mass Airflow Sensor circuit open or
poor connections Correct or replace
Mass Airflow Sensor defective Replace
Engine Coolant Temperature Sensor
circuit open or poor connections Correct or replace
Engine Coolant Temperature Sensor
defective Replace
Intake Air Temperature sensor circuit
open or poor connections Correct or replace
Intake Air Temperature sensor
defective Replace
Vehicle Speed Sensor circuit open or
shorted Correct or replace
Vehicle Speed Sensor defective Replace
Trouble in emission control system EGR valve defective Replace
EGR valve circuit open or poor
connection Correct or replace
Engine Control Module defective Replace
Canister purge valve circuit open or
poor connections Correct or replace
Canister purge valve defective Replace
Evaporative Emission Canister Purge
control valve defective Replace
Trouble in ignition system Refer to “Hard Start"
Others Engine lacks compression Refer to “Hard Start"
Valve incorrectly seated Lap valve
Air Cleaner Filter clogged Replace filter element
Valve timing incorrect Readjust
Idle air control valve broken Replace
Fast idle solenoid defective Replace
Positive Crankcase Ventilation valve
defective or clogged Replace

ENGINE MECHANICAL (6VE1 3.5L) 6A-7
Rough Engine Running
Symptom Possible Cause Action
Engine misfires periodically Ignition coil layer shorted Replace
Spark plugs fouling Clean or install hotter type plug
Spark plug(s) insulator nose leaking Replace
Fuel injector(s) defective Replace
Engine control module faulty Replace
Engine knocks periodically Spark plugs running too hot Install colder type spark plugs
Engine control module faulty Replace
Engine lacks power Spark plugs fouled Clean
Fuel injectors defective Replace
Mass Airflow Sensor or Intake Airflow
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

ENGINE MECHANICAL (6VE1 3.5L) 6A-9
Symptom Possible Cause Action
Hesitation at high speeds Engine Control Module defective Replace
Throttle Position Sensor cable broken
or poor connections 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
Mass Airflow Sensor circuit open or
poor connections Correct or replace
Mass Airflow Sensor defective Replace
IAT Sensor circuit open or poor
connections Correct or replace
IAT Sensor defective Replace
Throttle valve not fully opened Check and correct or replace
Air Cleaner Filter clogged Replace filter element
Power supply voltage too low Check and correct or replace

6A-10 ENGINE MECHANICAL (6VE1 3.5L)
Engine Lacks Power
Symptom Possible Cause Action
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 broken
or poor connections Correct or replace
Throttle Position Sensor defective Replace
Mass Airflow Sensor not working
normally 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 kinked or flattened Correct or replace
Exhaust system clogged Correct or replace
Ignition failure ———— Refer to Hard Start Troubleshooting
Guide
Heat range of spark plug inadequateInstall spark plugs of adequate heat
range
Ignition coil defective Replace

ENGINE MECHANICAL (6VE1 3.5L) 6A-15
Abnormal Combustion
Symptom Possible Cause Action
Trouble in fuel system Fuel pressure control valve defectiveReplace
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
broken or poor connections Reconnect, correct or replace
Mass Airflow (MAF) Sensor circuit
open or defective Correct or replace
MAF Sensor defective Replace
Engine Coolant Temperature (ECT)
Sensor circuit open or shorted Correct or replace
ECT Sensor defective Replace
Throttle Position Sensor adjustment
incorrect Readjust
Throttle Position Sensor defective Replace
Throttle Position Sensor connector
poor connections Reconnect
Vehicle Speed Sensor cable poor
connections 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 poor
connections or defective Correct or replace

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

6B-2 ENGINE COOLING (6VE1 3.5L)
General Description



030RW001
Legend (7)Cylinder Head
(1) Water Pump (8) Right Bank
(2) Thermostat (9) Throttle Body
(3) Radiator (10) Cylinder Block
(4) Reserve Tank (11) Cylinder Head
(5) Cooling Fan (12) Left Bank
(6) Cylinder Block (13) Heater


The engine cooling system consists of the radiator, the
water pump, the cooling fan, and the thermostat.
To quickly increase cold engine coolant temperature fo
r
smooth engine operation, the coolant is circulated by
the water pump and thermostat through the bypass
hose and back to the cylinder body.
The coolant does not circulate through the radiator.
When the coolant temperature reaches specified value,
the thermostat will begin to open and a gradually
increasing amount of coolant will circulate through the
radiator.
The thermostat will be fully open when the coolan
t
temperature reaches specified value. All of the coolant
is now circulating through the radiator for effective
engine cooling.

ENGINE COOLING (6VE1 3.5L) 6B-5
Diagnosis
Engine Cooling Trouble
Symptom Possible Cause Action
Engine overheating Low Engine Coolant level Replenish
Thermo meter unit faulty Replace
Faulty thermostat Replace
Faulty Engine Coolant temperature
sensor Repair or replace
Clogged radiator Clean or replace
Faulty radiator cap Replace
Low engine oil level or use of
improper engine oil Replenish or change oil
Clogged exhaust system Clean exhaust system or replace
faulty parts
Faulty Throttle Position sensor Replace throttle valve assembly
Open or shorted Throttle Position
sensor circuit Repair or replace
Damaged cylinder head gasket Replace
Engine overcooling Faulty thermostat Replace
Engine slow to warm–up Faulty thermostat Replace
Thermo unit faulty Replace