2004 ISUZU TF SERIES coolant temperature

6E-212 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Condition For Setting The DTC and Action Taken When The DTC Sets
Flash
Code Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P0171 B O2 Sensor System Too
Lean (Bank 1) 44

P0174 B O2 Sensor System Too
Lean (Bank 2) 1. No DTC relating to MAF sensor, IAT sensor, ECT sensor,
TPS, CMP sensor, CKP sensor, VSS, injector control
circuit, ignition control circuit, O2 sensor circuit low voltage
& high voltage (bank 1 & 2) and O2 sensor circuit no
activity (bank 1 & 2).
2. Engine speed is more than 600rpm.
3. Intake air temperature is more than 50
C.
4. Engine coolant temperature is between 35
C and 120
C.
5. Engine load is more than 20%.
6. EVAP purge solenoid valve on-duty is below 100%.
7. Air-fuel ratio correction volume is more than 150%
for 20 seconds. No fail-safe function.




CIRCUIT DESCRIPTION
To provide the best possible combination of driveability,
fuel economy, and emission control, a “closed loop"
air/fuel metering system is used. While in “closed loop,"
the Engine Control Module (ECM) monitors the HO2S
signals and adjusts fuel delivery based upon the HO2S
signal voltages. A change made to fuel delivery will be
indicated by the long and short term fuel trim values
which can be monitored with a Tech 2. Ideal fuel trim
values are around 0%; if the HO2S signals are
indicating a lean condition the ECM will add fuel,
resulting in fuel trim values above 0%. If a rich condition
is detected, the fuel trim values will be below 0%,
indicating that the ECM is reducing the amount of fuel
delivered. If an excessively lean condition is detected,
the ECM will set DTC P0171 or P0174.
The ECM's maximum authority to control long term fuel
trim allows a range between –15% (automatic
transmission) or –12% (manual transmission) and
+20%. The ECM monitors fuel trim under various
engine speed/load fuel trim cells before determining the
status the fuel trim diagnostic.

DIAGNOSTIC AIDS
Check for the following conditions:
 Poor connection at ECM – Inspect harness
connectors for backed-out terminals, imprope
r
mating, broken locks, improperly formed or damaged
terminals, and poor terminal-to-wire connection.
 Damaged harness – Inspect the wiring harness fo
r
damage. If the harness appears to be OK, observe
the HO2S display on the Tech 2 while moving
connectors and wiring harnesses related to the
engine harness. A change in the display will indicate
the location of the fault.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-217
Condition For Setting The DTC and Action Taken When The DTC Sets
Flash
Code Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P0172 B O2 Sensor System Too
Rich (Bank 1) 45
P0175 B O2 Sensor System Too
Rich (Bank 2) 1. No DTC relating to MAF sensor, IAT sensor, ECT sensor,
TPS, CMP sensor, CKP sensor, VSS, injector control
circuit, ignition control circuit, O2 sensor circuit low voltage
& high voltage (bank 1 & 2) and O2 sensor circuit no
activity (bank 1 & 2).
2. Engine speed is more than 600rpm.
3. Intake air temperature is more than 50
C.
4. Engine coolant temperature is between 35
C and 120
C.
5. Engine load is more than 20%.
6. EVAP purge solenoid valve on-duty is below 100%.
7. Air-fuel ratio correction volume is below 50% for 20
seconds. No fail-safe function.


CIRCUIT DESCRIPTION
To provide the best possible combination of driveability,
fuel economy, and emission control, a “closed loop"
air/fuel metering system is used. While in “closed loop,"
the Engine Control Module (ECM) monitors the heated
oxygen sensors (HO2S) signals and adjusts fuel
delivery based upon the HO2S signal voltages.
A
change made to fuel delivery will be indicated by the
long and short term fuel trim values which can be
monitored with a Tech 2. Ideal fuel trim values are
around 0%; if the HO2S signals are indicating a lean
condition the ECM will add fuel, resulting in fuel trim
values above 0%. If a rich condition is detected, the fuel
trim values will be below 0%, indicating that the ECM is
reducing the amount of fuel delivered. If an excessively
rich condition is detected on Bank 1, the ECM will se
t
DTC P0172 or P0175.
The ECM's maximum authority to control long term fuel
trim allows a range between –15% (automatic
transmission) or –12 (manual transmission) and +20%.
The ECM's maximum authority to control short term fuel
trim allows a range between –11% and +20%. The ECM
monitors fuel trim under various engine speed/load fuel
trim cells before determining the status of the fuel trim
diagnostic.

DIAGNOSTIC AIDS
Check for the following conditions:
 Poor connection at ECM – Inspect harness
connectors for backed-out terminals, imprope
r
mating, broken locks, improperly formed or damaged
terminals, and poor terminal-to-wire connection.
 Damaged harness –Inspect the wiring harness fo
r
damage. If the harness appears to be OK, observe
the HO2S display on the Tech 2 while moving
connectors and wiring harnesses related to the
engine harness. A change in the display will indicate
the location of the fault.

6E-222 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Condition For Setting The DTC and Action Taken When The DTC Sets
Flash
Code Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P1171 D Fuel Supply System
Lean During Power
Enrichment (Bank 1) 44

P1172 D Fuel Supply System
Lean During Power
Enrichment (Bank 2) 1. No DTC relating to MAF sensor, IAT sensor, ECT sensor,
TPS, CMP sensor, CKP sensor, VSS, injector control
circuit, ignition control circuit, O2 sensor circuit low voltage
& high voltage (bank 1 & 2) and O2 sensor circuit no
activity (bank 1 & 2).
2. Engine speed is between 1000rpm and 6000rpm.
3. Intake air temperature is below 70
C.
4. Engine coolant temperature is between 30
C and 120
C.
5. Engine load is between 150 and 255.
6. Throttle position output is more than 2.22V and fluctuation
is below 0.28V.
7. Except fuel cut operation.
8. O2 sensor output voltage below 250mV for 10 seconds. No fail-safe function.


CIRCUIT DESCRIPTION
The engine control module (ECM) internal circuitry can
identify if the vehicle fuel system is capable of supplying
adequate amounts of fuel during heavy acceleration
(power enrichment). The ECM monitors the voltage o
f
the oxygen sensor during power enrichment. When a
power enrichment mode of operation is requested
during “closed loop" operation (by heavy acceleration),
the ECM will provide more fuel to the engine. Unde
r
these conditions the ECM should detect a “rich"
condition (high oxygen sensor voltage). If this “rich"
exhaust is not detected at this time, a DTC P1171 o
r
P1172 will set. A plugged fuel filter, restricted fuel line,
restricted in-tank filter or defective fuel pump can
prevent adequate amouts of fuel from being supplied
during power enrichment mode.

DIAGNOSTIC AIDS
 A restricted fuel filter or fuel line, restricted in-tank
filter, or a defective fuel pomp may supply adequate
amounts of fuel at idle, but may not be able to supply
enough fuel during heavy acceleration.
 Water or alcohol in the fuel may cause low HO2S
voltage during acceleration.
 Check for faulty or plugged fuel injector(s).
 Check for low fuel.

6E-258 3.5L ENGINE DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) P0404 (FLASH CODE 32) EGR CIRCUIT
RANGE/PERFOMANCE (OPEN VALVE)
DIAGNOSTIC TROUBLE CODE (DTC) P1404 (FLASH CODE 32) EGR CIRCUIT
RANGE/PERFOMANCE (CLOSED VALVE)



RUW46EMF000201

Condition For Setting The DTC and Action Taken When The DTC Sets
Flash
Code Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P0404 B EGR Circuit
Range/Performance
(Open Valve) 1. Engine is stopping.
2. No DTC relating to ECT sensor, CKP sensor and VSS.
3. Vehicle speed is below 4km/h.
4. Engine coolant temperature is more than 75
C.
5. EGR solenoid valve on-duty ratio is more than 100%.
6. EGR valve output monitoring signal high. 32

P1404 B EGR Circuit
Range/Performance
(Closed Valve) 1. Engine is running.
2. Engine speed is below 4000rpm.
3. No DTC relating to CKP sensor.
4. EGR solenoid valve on-duty ratio is 0%.
5. EGR valve output monitoring signal low. 1. EGR operation is stopped.
2. EGR valve closed position
learning operation is disabled.
3. EGR position feedback is
disabled.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-297
Condition For Setting The DTC and Action Taken When The DTC Sets
Flash
Code Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P1508 B Idle Air Control System
Low/Closed 1. No DTC relating to MAF sensor, IAT sensor, ECT sensor,
TPS, CMP sensor, CKP sensor, VSS and system voltage.
2. Engine speed is between 675rpm and 6000rpm.
3. Engine coolant temperature is more than 75
C.
4. Intake air temperature is between -10
C and 80
C.
5. Vehicle is stopping.
6. Small amount of intake air through the idle air control
valve. (Idle air control valve is sticking at close position.)
Above conditions are met for 2 seconds. 22
P1509 B Idle Air Control System
High/Open 1. No DTC relating to MAF sensor, IAT sensor, ECT sensor,
TPS, CMP sensor, CKP sensor, VSS and system voltage.
2. Engine speed is between 675rpm and 6000rpm.
3. Engine coolant temperature more than 75
C.
4. Intake air temperature is between -10
C and 80
C.
5. Vehicle is stopping.
6. Large amount of intake air through the idle air control
valve. (Idle air control valve is sticking at open position.)
Above conditions are met for 2 seconds. Fuel cut is operated at high idle
speed.

CIRCUIT DESCRIPTION
The engine control module (ECM) controls engine idle
speed by adjusting the position of the idle air control
(IAC) motor pintle. The IAC is a bi-directional steppe
r
motor driven by two coils. The ECM applies current to
the IAC coils in steps (counts) to extend the IAC pintle
into a passage in the throttle body to decrease air flow.
The ECM reverses the current to retract the pintle,
increasing air flow. This method allows highly accurate
control of idle speed and quick response to changes in
engine load. If the ECM detects a condition where too
low of an idle speed is present and the ECM is unable
to adjust idle speed by increasing the IAC counts, DTC
P1508 or P1509 will set, indicating a problem with the
idle control system.

DIAGNOSTIC AIDS
Check for the following conditions:
 Poor connection at ECM or IAC motor –Inspec
t
harness connectors for backed-out terminals,
improper mating, broken locks, improperly formed o
r
damaged terminals, and poor terminal-to-wire
connection.
 Damaged harness – Inspect the wiring for damage.
 Restricted air intake system – Check for a possible
collapsed air intake duct, restricted air filter element,
or foreign objects blocking the air intake system.

6E-370 3.5L ENGINE DRIVEABILITY AND EMISSIONS
ENGINE COOLANT TEMPERATURE
(ECT) SENSOR

Location
Installed to the thermostat housing.

Removal Procedure
1. Disconnect the negative battery cable.
2. Drain enough engine coolant so that the coolan
t
level will be below the ECT sensor.
3. Disconnect connector from the ECT sensor.
4. Loosen and remove the ECT sensor from the
thermostat housing.
NOTE:
Cool down the engine before above procedures are
carried out.










Installation Procedure
1. Apply sealer to threads of screw at the ECT
sensor.
2. Tighten the ECT sensor with specified tightening
torque.
Tightening Torque





13N




m (1.3kgf




m)
3. Connect a ECT sensor connector to the ECT
sensor.
4. Fill the engine coolant.
5. Connect the negative battery cable.

NOTE:
Verify any DTCs (diagnosis Trouble Code) are not
stored after replacement.
Verify no engine coolant leaking from the senso
r
threads after replacement.


MASS AIR FLOW (MAF) SENSOR &
INTAKE AIR TEMPERATURE (IAT)
SENSOR
Location
Installed to the intake duct housing.

Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect a MAF & IAT sensor connector from
the MAF & IAT sensor.
3. Loosen two screws and remove the MAF & IAT
sensor from the intake duct.





Installation Procedure
1. Install the MAF & IAT sensor into intake air duct.
2. Tighten MAF & IAT sensor by two screws.
Tightening Torque : 1.5 N




m (0.15 kgf




m)
3. Connect a sensor connector to the MAF & IAT
sensor.
4. Connect the negative battery cable.

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

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