2004 ISUZU TF SERIES switch

6E–10 ENGINE DRIVEABILITY AND EMISSIONS
(1) Canister(1)
(2)Fuel Tank
Fuel Pump
2 1
(1)
(2)Vehicle Speed Sensor (VSS)
Transmission Assembly
12
(1)
(2)Power Steering Pressure Switch
Power Steering Oil Pump Assembly
12

6E–28 ENGINE DRIVEABILITY AND EMISSIONS
CONNECTOR LIST
No. Connector face No. Connector face
B-24
Green Meter-BC-122
CO Adjuster
B-58
Black Check connectorE-6
Fuel injector
B-62
White Ignition switch (IGSUB : G1)E-7
Fuel injector
B-63
White Ignition switch (IGSUB : G2)E-8
Fuel injector
B-68
ImmobilizerE-9
Fuel injector
C-2
Silver Engine room-RH groundE-18
Ignition coil
C-56
ECME-60
ECM
C-107
White J/B E2E-72
Engine earth-A
C-108
White J/B E1E-74
Engine earth-B
C-121
IAT sensorE-77
O
2 sensor

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

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)

6E–58 ENGINE DRIVEABILITY AND EMISSIONS
Damaged EVAP canister
Leaking fuel sender assembly O-ring
Leaking fuel tank or fuel filler neck
The ECM supplies a ground to energize the purge
control solenoid valve (purge “ON” ). The EVAP purge
control is turned “ON” and “OFF,” several times a
second. The duty cycle (pulse width) is determined by
engine operating conditions including load, throttle
position, coolant temperature and ambient temperature.
The duty cycle is calculated by the ECM and the output
is commanded when the appropriate conditions have
been met.
The system checks for conditions that cause the EVAP
system to purge continuously by commanding the EVAP
purge solenoid “OFF”, EVAP purge solenoid duty ratio
“0%”. If fuel tank vacuum level increases during the test,
a continuous purge flow condition is indicated. This can
be caused by the following conditions:
EVAP purge solenoid leaking
EVAP purge and engine vacuum lines switched at the
EVAP purge control solenoid valve
EVAP purge control solenoid valve driver circuit
grounded

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.

ENGINE DRIVEABILITY AND EMISSIONS 6E–63
3. Check Bulletins and
Troubleshooting Hints
NOTE: As estimated 30 percent of successful vehicle
repairs are diagnosed with this step!
What you should do
You should have enough information gained from
preliminary checks to accurately search for a bulletin
and other related service information. Some service
manual sections provide troubleshooting hints that
match symptoms with specific complaints.
What resources you should use
You should use the following resources for assistance in
checking for bulletins and troubleshooting hints:
Printed bulletins
Access ISUZU Bulletin Web site.
Videotapes
Service manual
4. Perform Service Manual
Diagnostic Checks
What you should do
The “System Checks” in most service manual sections
and in most cells of section 8A (electrical) provide you
with:
A systematic approach to narrowing down the
possible causes of a system fault
Direction to specific diagnostic procedures in the
service manual
Assistance to identify what systems work correctly
What resources you should use
Whenever possible, you should use the following
resources to perform service manual checks:
Service manual
Technical equipment (for viewing DTCs and
analyzing data)
Digital multimeter and circuit testing tools
Other tools as needed
5a and 5b. Perform Service Manual
Diagnostic Procedures
NOTE: An estimated 40 percent of successful vehicle
repairs are diagnosed with these steps!
What you should do
When directed by service manual diagnostic checks,
you must then carefully and accurately perform the
steps of diagnostic procedures to locate the fault relatedto the customer complaint.
What resources you should use
Whenever appropriate, you should use the following
resources to perform service manual diagnostic
procedures:
Service manual
Technical equipment (for analyzing diagnostic data)
Digital multimeter and circuit testing tools
Essential and special tools
5c. Technician Self Diagnoses
When there is no DTC stored and no matching
symptom for the condition identified in the service
manual, you must begin with a thorough understanding
of how the system(s) operates. Efficient use of the
service manual combined with you ex perience and a
good process of elimination will result in accurate
diagnosis of the condition.
What you should do
Step 1: Identify and understand the suspect
circuit(s)
Having completed steps 1 through 4 of the Strategy
Based Diagnostics chart, you should have enough
information to identify the system(s) or sub-system(s)
involved. Using the service manual, you should
determine and investigate the following circuit
characteristics:
Electrical:
–How is the circuit powered (power distribution
charts and/or fuse block details)?
–How is the circuit grounded (ground distribution
charts)?
–How is the circuit controlled or sensed (theory of
operation):
–If it is a switched circuit, is it normally open or
normally closed?
–Is the power switched or is the ground
switched?
–Is it a variable resistance circuit (ECT sensor
or TP sensor, for ex ample)?
–Is it a signal generating device (MAF sensor of
VSS, for example)?
–Does it rely on some mechanical/vacuum
device to operate?
Physical:
–Where are the circuit components (component
locators and wire harness routing diagrams):
–Are there areas where wires could be chafed
or pinched (brackets or frames)?
–Are there areas subjected to ex treme
temperatures?

6E–64 ENGINE DRIVEABILITY AND EMISSIONS
–Are there areas subjected to vibration or
movement (engine, transmission or
suspension)?
–Are there areas ex posed to moisture, road salt
or other corrosives (battery acid, oil or other
fluids)?
–Are there common mounting areas with other
systems/components?
–Have previous repairs been performed to wiring,
connectors, components or mounting areas
(causing pinched wires between panels and
drivetrain or suspension components without
causing and immediate problem)?
–Does the vehicle have aftermarket or dealer-
installed equipment (radios, telephone, etc.)
Step 2: Isolate the problem
At this point, you should have a good idea of what could
cause the present condition, as well as could not cause
the condition. Actions to take include the following:
Divide (and separate, where possible) the system or
circuit into smaller sections
Confine the problem to a smaller area of the vehicle
(start with main harness connections while removing
panels and trim as necessary in order to eliminate
large vehicle sections from further investigation)
For two or more circuits that do not share a common
power or ground, concentrate on areas where
harnesses are routed together or connectors are
shared (refer to the following hints)
Hints
Though the symptoms may vary, basic electrical failures
are generally caused by:
Loose connections:
–Open/high resistance in terminals, splices,
connectors or grounds
Incorrect connector/harness routing (usually in new
vehicles or after a repair has been made):
–Open/high resistance in terminals, splices,
connectors of grounds
Corrosion and wire damage:
–Open/high resistance in terminals, splices,
connectors of grounds
Component failure:
–Opens/short and high resistance in relays,
modules, switches or loads
Aftermarket equipment affecting normal operation of
other systems
You may isolate circuits by:
Unplugging connectors or removing a fuse to
separate one part of the circuit from another part
Operating shared circuits and eliminating those that
function normally from the suspect circuit
If only one component fails to operate, begin testingat the component
If a number of components do no operate, begin tests
at the area of commonality (such as power sources,
ground circuits, switches or major connectors)
What resources you should use
Whenever appropriate, you should use the following
resources to assist in the diagnostic process:
Service manual
Technical equipment (for data analysis)
Ex perience
Technical Assistance
Circuit testing tools
5d. Intermittent Diagnosis
By definition, an intermittent problem is one that does
not occur continuously and will occur when certain
conditions are met. All these conditions, however, may
not be obvious or currently known. Generally,
intermittents are caused by:
Faulty electrical connections and wiring
Malfunctioning components (such as sticking relays,
solenoids, etc.)
EMI/RFI (Electromagnetic/radio frequency
interference)
Aftermarket equipment
Intermittent diagnosis requires careful analysis of
suspected systems to help prevent replacing good
parts. This may involve using creativity and ingenuity to
interpret customer complaints and simulating all
ex ternal and internal system conditions to duplicate the
problem.
What you should do
Step 1: A cquire information
A thorough and comprehensive customer check sheet
is critical to intermittent problem diagnosis. You should
require this, since it will dictate the diagnostic starting
point. The vehicle service history file is another
source for accumulating information about the
complaint.
Step 2: A nalyze the intermittent problem
Analyze the customer check sheet and service history
file to determine conditions relevant to the suspect
system(s).
Using service manual information, you must identify,
trace and locate all electrical circuits related to the
malfunctioning system(s). If there is more than one
system failure, you should identify, trace and locate
areas of commonality shared by the suspect circuits.