turn signal ISUZU TF SERIES 2004 Service Manual

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-317
DIAGNOSTIC TROUBLE CODE (DTC) P1626 IMMOBILIZER NO SIGNAL



RTW46EMF000301

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)
67 P1626 - Immobilizer No Signal No response from immobilizer control unit. 1. Engine does not start.
2. Check engine lamp flash.

CIRCUIT DESCRIPTION
The Engine Control Module (ECM) decides whether that
is an abnomality in the immobilizer control system. DTC
P1626 is recorded by the ECM when no response from
immoblizer.

DIAGNOSTIC AIDS
Check for the following conditions:

Poor connection at Engine Control Module (ECM)
and immobilizer inspect harness connectors for
backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal to wire connection.

Damaged harness-inspect the wiring harness for
damage, if the harness appears to be OK,
disconnect the ECM and immobilizer, turn the
ignition "ON" and observe a voltmeter connected to
the suspect driver circuit at the ECM and immobilizer
harness connector while moving connectors and
wiring harnesses relates to the Check Engine Lamp
(MIL). A change in voltage will indicate the location
of the fault.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-323
DIAGNOSTIC TROUBLE CODE (DTC) P1631 IMMOBILIZER WRONG SIGNAL



RTW46EMF000301

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)
67 P1631 - Immobilizer Wrong
Signal Received response is not correct. 1. Engine does not start.
2. Check engine lamp flash.

CIRCUIT DESCRIPTION
The ECM decides whether that is an abnormality in the
immobilizer control system. DTC P1631 is recorded by
the ECM when received response was not correct.

DIAGNOSTIC AIDS
Check for the following conditions:

Poor connection at Engine Control Module (ECM)
and immobilizer inspect harness connectors for
backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal to wire connection.

Damaged harness-inspect the wiring harness for
damage, if the harness appears to be OK,
disconnect the ECM and immobilizer, turn the
ignition "ON" and observe a voltmeter connected to
the suspect driver circuit at the ECM and immobilizer
harness connector while moving connectors and
wiring harnesses relates to the Check Engine Lamp
(MIL). A change in voltage will indicate the location
of the fault.

6C-4 ENGINE FUEL (C24SE)

Fuel Metering
Engine Control Module (ECM) is in complete control of this fuel
delivery system during normal driving conditions.
The intake manifold function, like that of a diesel, is used only
to let air into the engine. The fuel is injected by separate
injectors that are mounted over the intake manifold.
The Manifold Absolute Pressure (MAP) sensor measures the
changes in the intake manifold pressure which result from
engine load and speed changes, which the MAP senso
r
converts to a voltage output.
This sensor generates the voltage to change corresponding to
the flow of the air drawn into the engine.
The changing voltage is transformed into an electric signal and
provided to the ECM.
With receipt of the signals sent from the MAP sensor, Intake
Air Temperature sensor and others, the ECM determines an
appropriate fuel injection pulse width feeding such information
to the fuel injector valves to effect an appropriate air/fuel ratio.
The Multiport Fuel Injection system utilizes an injection system
where the injectors turn on at every crankshaft revolution. The
ECM controls the injector on time so that the correct amount o
f
fuel is metered depending on driving conditions.
Two interchangeable "O" rings are used on the injector tha
t
must be replaced when the injectors are removed.
The fuel rail is attached to the top of the intake manifold and
supplies fuel to all the injectors.
Fuel is recirculated through the rail continually while the engine
is running. This removes air and vapors from the fuel as well
as keeping the fuel cool during hot weather operation.
The fuel pressure control valve that is mounted on the fuel rail
maintains a pressure differential across the injectors under all
operating conditions. It is accomplished by controlling the
amount of fuel that is recirculated back to the fuel tank based
on engine demand.
See Section "Driveability and Emission" for more information
and diagnosis.

6E–44 ENGINE DRIVEABILITY AND EMISSIONS
Connector J2 Port: View Looking Into ECM Case
1
1716
32
PIN32
PIN1 PIN17
PIN16
Pin
No. B/
Box
No.Pin FunctionWire
ColorSignal or Continuity
ECM
ConnectionTester Position
Key SW
OffKey SW
OnEngine
IdleEngine
2000rpmRange (+) (-)
J2-1 J2-1 Inta ke Air Temp. (IAT)
Sensor GroundGRN Continuity
with
ground- - - Disconnect
J2-1 GND
J2-2 J2-2 Batte ry Powe r Supply RED/
WH T10-14V Co nnect DC V J2-2 GND
J2-3 J2-3 Ignitio n Powe r Supply BLU/
YELLess than
1V10-14V Connect DC V J2-3 GND
J2-4 J2-4 To Da ta Link
Conne ctor No. 6BLU - - - - - - - -
J2-5 J2-5 No Connection - - - - - - - - -
J2-6 J2-6 Oxy ge n Se nsor
(Ground)PNK Continuity
with
ground- - - Connect
J2-6 GND
J2-7 J2-7 No Connection - - - - - - - - -
J2-8 J2-8 No Connection - - - - - - - - -
J2-9 J2-9 No Connection - - - - - - - - -
J2-10 J2-10 CO Adjust Signa l
(W/O Cata ly stic
Converter)YEL - - - - - - - -
J2-11 J2-11 Fuel Pump Re la y GRN/
WH T10-14V
While relay
is activated;
10-14V
R elay is no t
activated;
Less than
1V10-14V Connect DC V J2-11 GND
J2-12 J2-12 No Connection - - - - - - - - -
J2-13 J2-13 A/C Compre sso r
RelayGRY/
REDLess than
1VA/C comp. is operated: Less than 1V
A/C comp. is not operated: 10-14VCo nnect DC V J2-13 GND
J2-14 J2-14 No Connection - - - - - - - - -
J2-15 J2-15 No Connection - - - - - - - - -
J2-16 J2-16 No Connection - - - - - - - - -
J2-17 J2-17 CO Adjust (W/O
Cata ly stic Conv erter)RED - - - - - - - -
J2-18 J2-18 Batte ry Powe r Supply RED/
WH T10-14V Co nnect DC V J2-18 GND
J2-19 J2-19 No Connection - - - - - - - - -
J2-20 J2-20 Pow er Ste ering
Pressure SwitchGRN/
YELLess than
1V
Pressure switch is turned on: Less than 1V
Pressure switch is turned off: 10-14VCo nnect DC V J2-20 GND
J2-21 J2-21 Oxygen Sensor BLU Less than
1VApprox .
0.4VWave form D or 0.1 -
0.9V Co nnect DC V J2-21 J2-6
J2-22 J2-22 Inta ke Air Temp. (IAT)
Sensor (Signa l)YEL/
GRNLess than
1V
20
: Approx. 2.9V / 40
: Approx . 1.8V V
/ 60
: Approx. 1.1V / 80
: Approx . 0.6VCo nnect DC V J2-22 33

ENGINE DRIVEABILITY AND EMISSIONS 6E–45
J2-23 J2-23 Vehicle Speed Sensor
(VSS) Signal
(Immobilize r Co ntrol
Unit Terminal B8)WHT - - Wave form C or Approx.
6.5V at 20km/hCo nnect AC V J2-23 GND
J2-24 J2-24 No Connection - - - - - - - - -
J2-25 J2-25 Ta cho me te r Output
Signa lBLK/
RED- - Wa v e f o r m Wa v e f o r m
B or
Approx.
4.5VCo nnect AC V J2-25 GND
J2-26 J2-26 Thermo Relay GRN/
BLKLess than
1V
A/C request is activ ated: 10-14V
A/C request is not activated: Less than 1VCo nnect DC V J2-26 GND
J2-27 J2-27 No Connection - - - - - - - - -
J2-28 J2-28 No Connection - - - - - - - - -
J2-29 J2-29 No Connection - - - - - - - - -
J2-30 J2-30 To Da ta Link
Conne ctor No. 2GRN - - - - - - - -
J2-31 J2-31 Oxy ge n Se nso r He ater BLU/
WH TContinuity
with
ground- Wave
FormWa v e
Form DConnect
J2 -31 GND
J2-32 J2-32 Check Engine Lamp
(Immobilize r Co ntrol
Unit Terminal B7)BRN/
YELLess than
1VLess than
1VLa mp is turne d on: Less
than 1V
Lamp is turne d off: 10-
14VCo nnect DC V J2-32 GND Pin
No. B/
Box
No.Pin FunctionWire
ColorSignal or Continuity
ECM
ConnectionTester Position
Key SW
OffKey SW
OnEngine
IdleEngine
2000rpmRange (+) (-)

6E–48 ENGINE DRIVEABILITY AND EMISSIONS
GENERAL DESCRIPTION FOR ECM AND
SENSORS
Engine Control Module (ECM)
The engine control module (ECM) is located on the
intake manifold. The ECM controls the following.
Fuel metering system
Ignition timing
On-board diagnostics for electrical functions.
The ECM constantly observes the information from vari-
ous sensors. The ECM controls the systems that affect
vehicle performance. And it performs the diagnostic
function of the system.
The function can recognize operational problems, and
warn to the driver through the check engine lamp, and
store diagnostic trouble code (DTC). DTCs identify the
problem areas to aid the technician in marking repairs.
The input / output devices in the ECM include analog to
digital converts, signal buffers, counters and drivers.
The ECM controls most components with electronic
switches which complete a ground circuit when turned
on.
Inputs (Operating condition read):
Battery voltage
Electrical ignition
Ex haust oxygen content
Intake manifold pressure
Intake air temperature
Engine coolant temperature
Crankshaft positionKnock signal
Throttle position
Vehicle speed
Power steering pressure
Air conditioning request on or off
Outputs (Systems controlled):
Ignition control
Fuel control
Idle air control
Fuel pump
EVAP canister purge
Air conditioning
Diagnostics functions
Manifold Absolute Pressure (MAP) Sensor
The MAP sensor is a strain gage. A pressure strains the
resistance on the silicon base. At that time the
resistance value changes. And it changes voltage. In
other words it measures a pressure value. It is installed
to the intake manifold. Output voltage of the MAP
sensor is low as pressure is low. (1) J1 Port
(2) J2 Port
12
C h arac teris tic of MA P S ens or -R ef erenc e-
0 0.51 1.52 2.53 3.54 4.55
15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105
Mani fold A bs olute P res s ure (K P a) (T ec h2 Reading)
Output Voltage (V)

ENGINE DRIVEABILITY AND EMISSIONS 6E–51
Intake Air Temperature (IAT) Sensor
The IAT sensor is a thermistor. A temperature changes
the resistance value. And it changes voltage. In other
words it measures a temperature value. Low air
temperature produces a high resistance.
The ECM supplies 5 volts signal to the IAT sensor
through resisters in the ECM and measures the voltage.
The signal voltage will be high when the air temperature
is cold, and it will be low when the air temperature is
hot.
Vehicle Speed Sensor (VSS)
The VSS is a magnet rotated by the transmission output
shaft. The VSS uses a hall element. It interacts with the
magnetic field treated by the rotating magnet. It outputs
pulse signal. The 12 volts operating supply from the
meter fuse.
Heated Oxygen (O2) Sensor
The heated ox ygen sensor consists of a 4-wire low
temperature activated zirconia ox ygen analyzer element
with heater for operating temperature of 315°C, and
there is one mounted on each ex haust pipe.
A constant 450millivolt is supplied by the ECM between
the two supply terminals, and oxygen concentration in
the ex haust gas is reported to the ECM as returned
signal voltage.
The ox ygen present in the ex haust gas reacts with the
sensor to produce a voltage output. This voltage should
constantly fluctuate from approx imately 100mV to
1000mV and the ECM calculates the pulse width
commanded for the injectors to produce the proper
combustion chamber mix ture.
Low ox ygen sensor output voltage is a lean mix ture
which will result in a rich commanded to compensate.
High ox ygen sensor output voltage is a rich mix ture
which result in a lean commanded to compensate.
When the engine is first started the system is in “Open
Loop” operation. In “Open Loop”, the ECM ignores the
signal from the ox ygen sensors. When various
conditions (ECT, time from start, engine speed &
ox ygen sensor output) are met, the system enters
“Closed Loop” operation. In “Closed Loop”, the ECM
calculates the air fuel ratio based on the signal from the
ox ygen sensors.
Heated ox ygen sensors are used to minimize the
amount of time required for closed loop fuel control to
begin operation and allow accurate catalyst monitoring.
The ox ygen sensor heater greatly decreases the
amount of time required for fuel control sensors to
become active.
Oxygen sensor heaters are required by catalyst monitor
and sensors to maintain a sufficiently high temperature
which allows accurate ex haust ox ygen content readings
further away from the engine.
C haract erist ic of I A T Sen sor -Ref erence-
10 100 1000 10000 100000
- 20 - 10 0 10 20 30 40 50 60 70 80 90 100 110 120
I nt ake A i r T emp. ( deg . C ) ( Tec h2 R eadi ng )
Resistance (ohm) (Solid Line)

6E–52 ENGINE DRIVEABILITY AND EMISSIONS
GENERAL DESCRIPTION FOR FUEL
METERING
The fuel metering system starts with the fuel in the fuel
tank. An electric fuel pump, located in the fuel tank,
pumps fuel to the fuel rail through an in-line fuel filter.
The pump is designed to provide fuel at a pressure
above the pressure needed by the injectors.
A fuel pressure regulator in the fuel rail keeps fuel
available to the fuel injectors at a constant pressure.
A return line delivers unused fuel back to the fuel tank.
The basic function of the air/fuel metering system is to
control the air/fuel delivery to the engine. Fuel is
delivered to the engine by individual fuel injectors
mounted in the intake manifold.
The main control sensor is the heated ox ygen sensor
located in the ex haust system. The heated ox ygen
sensor reports to the ECM how much oxygen is in the
ex haust gas. The ECM changes the air/fuel ratio to the
engine by controlling the amount of time that fuel
injector is “On”.
The best mix ture to minimize exhaust emissions is 14.7
parts of air to 1 part of gasoline by weight, which allows
the catalytic converter to operate most efficiently.
Because of the constant measuring and adjusting of the
air/fuel ratio, the fuel injection system is called a “closed
loop” system.
The ECM monitors signals from several sensors in
order to determine the fuel needs of the engine. Fuel is
delivered under one of several conditions called “mode”.
All modes are controlled by the ECM.
Battery Voltage Correction Mode
When battery voltage is low, the ECM will compensate
for the weak spark by increasing the following:
The amount of fuel delivered.
The idle RPM.
Clear Flood Mode
Clear a flooded engine by pushing the accelerator pedal
down all the way. The ECM then de-energizes the fuel
injectors. The ECM holds the fuel injectors de-energized
as long as the throttle remains above 75% and the
engine speed is below 800 RPM. If the throttle position
becomes less than 75%, the ECM again begins to pulse
the injectors ON and OFF, allowing fuel into the
cylinders.
Deceleration Fuel Cutoff (DFCO) Mode
The ECM reduces the amount of fuel injected when it
detects a decrease in the throttle position and the air
flow. When deceleration is very fast, the ECM may cut
off fuel completely. Until enable conditions meet the
engine revolution less 1000 rpm or manifold absolute
pressure less than 10 kPa.
Engine Speed/ Vehicle Speed/ Fuel Disable
Mode
The ECM monitors engine speed. It turns off the fuel
injectors when the engine speed increases above 6000
RPM. The fuel injectors are turned back on when
engine speed decreases below 3500 RPM.
Acceleration Mode
The ECM provides ex tra fuel when it detects a rapid
increase in the throttle position and the air flow.
Fuel Cutoff Mode
No fuel is delivered by the fuel injectors when the
ignition is OFF. This prevents engine run-on. In addition,
the ECM suspends fuel delivery if no reference pulses
are detected (engine not running) to prevent engine
flooding.
Starting Mode
When the ignition is first turned ON, the ECM energizes
the fuel pump relay for two seconds to allow the fuel
pump to build up pressure. The ECM then checks the
engine coolant temperature (ECT) sensor and the
throttle position sensor to determine the proper air/fuel
ratio for starting.
The ECM controls the amount of fuel delivered in the
starting mode by adjusting how long the fuel injectors
are energized by pulsing the injectors for very short
times.
Run Mode
The run mode has the following two conditions:
Open loop
Closed loop
When the engine is first started, the system is in “open
loop” operation. In “Open Loop,” the ECM ignores the
signal from the heated oxygen sensor (HO2S). It
calculates the air/fuel ratio based on inputs from the TP,
ECT, and MAP sensors.
The system remains in “Open Loop” until the following
conditions are met:
The HO2S has a varying voltage output showing that
it is hot enough to operate properly (this depends on
temperature).
The ECT has reached a specified temperature.
A specific amount of time has elapsed since starting
the engine.
Engine speed has been greater than a specified RPM
since start-up.
The specific values for the above conditions vary with
different engines and are stored in the programmable
read only memory (PROM). When these conditions are
met, the system enters “closed loop” operation. In
“closed loop,” the ECM calculates the air/fuel ratio
(injector on-time) based on the signal from the HO2S.
This allows the air/fuel ratio to stay very close to 14.7:1.

ENGINE DRIVEABILITY AND EMISSIONS 6E–53
Fuel Metering System Components
The fuel metering system is made up of the following
parts.
Fuel injector
Throttle body
Fuel rail
Fuel pressure regulator
ECM
Crankshaft position (CKP) sensor
Idle air control (IAC) valve
Fuel pump
Fuel Injector
The group fuel injection fuel injector is a solenoid
operated device controlled by the ECM. The ECM
energizes the solenoid, which opens a valve to allow
fuel delivery.
The fuel is injected under pressure in a conical spray
pattern at the opening of the intake valve. Ex cess fuel
not used by the injectors passes through the fuel
pressure regulator before being returned to the fuel
tank.
Fuel Pressure Regulator
The fuel pressure regulator is a diaphragm-operated
relief valve mounted on the fuel rail with fuel pump
pressure on one side and manifold pressure on the
other side. The fuel pressure regulator maintains the
fuel pressure available to the injector at three times
barometric pressure adjusted for engine load. It may be
serviced separately.
If the pressure is too low or poor performance, DTC
P0131 or P1171 will be the result. If the pressure is too
high, DTC P0132 or P1167 will be the result. Refer to
Fuel System Diagnosis for information on diagnosing
fuel pressure conditions.
Fuel Rail
The fuel rail is mounted to the top of the engine and
distributes fuel to the individual injectors. Fuel is
delivered to the fuel inlet tube of the fuel rail by the fuel
lines. The fuel goes through the fuel rail to the fuel
pressure regulator. The fuel pressure regulator
maintains a constant fuel pressure at the injectors.
Remaining fuel is then returned to the fuel tank.
Fuel Pump Electrical Circuit
When the key is first turned ON, the ECM energizes the
fuel pump relay for two seconds to build up the fuel
pressure quickly. If the engine is not started within two
seconds, the ECM shuts the fuel pump off and waits
until the engine is cranked. When the engine is cranked
and the 58X crankshaft position signal has been
detected by the ECM, the ECM supplies 12 volts to the
fuel pump relay to energize the electric in-tank fuel
pump.
An inoperative fuel pump will cause a “no-start”
condition. A fuel pump which does not provide enoughpressure will result in poor performance.
Thottle Body Unit
The throttle body has a throttle plate to control the
amount of air delivered to the engine. The Thottle
position sensor and IAC valve are also mounted on the
throttle body.
Vacuum ports located behind the throttle plate provide
the vacuum signals needed by various components.
Engine coolant is directed through a coolant cavity in
the throttle body to warm the throttle valve and to
prevent icing.

6E–60 ENGINE DRIVEABILITY AND EMISSIONS
A/C CLUTCH DIAGNOSIS
A/C Clutch Circuit Operation
A 12-volt signal is supplied to the A/C request input of
the ECM when the A/C is selected through the A/C
control switch.
The A/C compressor clutch relay is controlled through
the ECM. This allows the ECM to modify the idle air
control position prior to the A/C clutch engagement for
better idle quality. If the engine operating conditions are
within their specified calibrated acceptable ranges, the
ECM will enable the A/C compressor relay. This is done
by providing a ground path for the A/C relay coil within
the ECM. When the A/C compressor relay is enabled,
battery voltage is supplied to the compressor relay is
enabled, battery voltage is supplied to the compressor
clutch coil.
The ECM will enable the A/C compressor clutch
whenever the engine is running and the A/C has been
requested. The ECM will not enable the A/C
compressor clutch if any of the following conditions are
met:
The engine speed is greater than 6000 RPM.
The ECT is greater than 122°C (251°F).
The throttle is more than 95% open.
A/C Clutch Circuit Purpose
The A/C compressor operation is controlled by the
engine control module (ECM) for the following reasons:
It improves idle quality during compressor clutch
engagement.
It improves wide open throttle (WOT) performance.
It provides A/C compressor protection from operation
with incorrect refrigerant pressures.
The A/C electrical system consists of the following
components:
The A/C control switch.
The A/C refrigerant pressure switches.
The A/C compressor clutch.
The A/C compressor clutch relay.
The ECM.
A/C Request Signal
This signal tells the ECM when the A/C mode is
selected at the A/C control switch. The ECM uses this
input to adjust the idle speed before turning on the A/C
clutch. The A/C compressor will be inoperative if this
signal is not available to the ECM.
Refer to A/C Clutch Circuit Diagnosis for A/C wiring
diagrams and diagnosis for the A/C electrical system.