power ISUZU TF SERIES 2004 Workshop Manual

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-45
Signal or Continuity Tester Position Pin
No.

B/Box
No.
Pin Function Wire
Color
Key SW
Off Key SW
On Engine
Idle Engine
2000rpmECM
Connection Range(+) (-)
A31 A31 No. 3 Ignition
Coil RED/
BLU - - Wave form - - - -
A32 A32 No. 1 Ignition
Coil RED - - Wave form - - - -
A33 A33 Ground (Power) BLK/
RED Continuity
with ground - - - Disconnect Ohm A33 GND
A34 A34 No. 5 Injector GRN/
BLK Less than 1V Wave form or 12-14V Connect DC V A34 GND
A35 A35 No. 3 Injector BLU Less than 1V Wave form or 12-14V Connect DC V A35 GND
A36 A36 No. 1 Injector GRN/
WHT Less than 1V Wave form or 12-14V Connect DC V A36 GND
A37 A37 Ground (Case) BLK/
RED Continuity
with ground - - - Disconnect Ohm A37 GND
A38 A38 No Connection - - - - - - - - -
A39 A39 No Connection - - - - - - - - -
A40 A40 No Connection - - - - - - - - -

6E-46 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Connector B Port: View Looking Into ECM Cace





Signal or Continuity Tester Position Pin
No. B/Box
No. Pin Function Wire
Color
Key SW Off Key SW On Engine IdleEngine
2000rpm ECM
Connection Range (+) (-)
B1 B1 No Connection - - - - - - - - -
B2 B2 No Connection - - - - - - - - -
B3 B3 No. 2 Injector GRN/
ORG Less than 1V Wave form or 12-14V Connect DC V B3 GND
B4 B4 No. 4 Injector GRN/
RED Less than 1V Wave form or 12-14V Connect DC V B4 GND
B5 B5 No. 6 Injector GRN/
YELLess than 1V Wave form or 12-14V Connect DC V B5 GND
B6 B6 Ground
(Power) BLK Continuity
with ground - - - Disconnect Ohm B6 GND
B7 B7 No. 2 Ignition
Coil RED/
BLK- - Wave form - - - -
B8 B8 No. 4 Ignition
Coil RED/
WHT - - Wave form - - - -
B9 B9 No. 6 Ignition
Coil RED/
GRN - - Wave form - - - -
B10 B10 No Connection - - - - - - - - -
B11 B11 A/C
Compressor
Relay GRY/
RED Less than 1V A/C comp. is operated: Less than 1V
A/C comp. is not operated: 10-14V Connect DC V B11 GND
B12 B12 Tachometer
Output Signal BLK/
RED - - Wave form or
6.2V Wave form or
6.2V Connect AC V B12 GND
B13 B13 Idle Air Control
(IAC) Valve
Coil A High BLU Less than 1V Less than 1V / 10-14V Connect DC V B13 GND
B14 B14 Idle Air Control
(IAC) Valve
Coil B High BLU/
WHT Less than 1V Less than 1V / 10-14V Connect DC V B14 GND
B15 B15 Canister Purge
Solenoid Valve RED/
BLULess than 1V Wave form or 12-14V Connect AC V B15 GND

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-47
Signal or Continuity Tester Position Pin
No. B/Box
No. Pin Function Wire
Color
Key SW Off Key SW On Engine IdleEngine
2000rpm ECM
Connection Range (+) (-)
B16 B16 Idle Air Control
(IAC) Valve
Coil A Low BLU/
RED Less than 1V Less than 1V / 10-14V Connect DC V B16 GND
B17 B17 Idle Air Control
(IAC) Valve
Coil B Low BLU/
BLKLess than 1V Less than 1V / 10-14V Connect DC V B17 GND
B18 B18 Check Engine
Lamp
(Immobilizer
Control Unit
Terminal B7) BRN/
YELLess than 1V Less than 1VLamp is turned on:
Less than 1V
Lamp is turned off: 10-14VConnect DC V B18 GND
B19 B19 Fuel Pump
Relay GRN/
WHT Less than 1V While relay is
activated:
10-14V
Relay is not
activated:
Less than 1V10-14V Connect DC V B19 GND
B20 B20 Mass Air Flow
(MAF) Sensor BLK/
YELLess than 1V Approx. 0.47VApprox. 1.5V
at 750 rpmApprox. 2V Connect DC V B20 GND
B21 B21 Bank 1 Oxygen
Sensor Signal PNK Less than 1V Approx. 0.4V 0.1 - 0.9V Connect DC V B21 B22
B22 B22 Bank 1 Oxygen
Sensor Ground BLU/
YELContinuity
with ground - - - Connect Ohm B22 GND
B23 B23 Bank 2 Oxygen
Sensor Signal RED Less than 1V Approx. 0.4V 0.1 - 0.9V Connect DC V B23 B24
B24 B24 Bank 2 Oxygen
Sensor Ground BLU/
BLKContinuity
with ground - - - Connect Ohm B24 GND
B25 B25 To Data Link
Connector
No.6 BLK/
GRN - - - - - - - -
B26 B26 Throttle
Position
Sensor (TPS)
Signal BLU Less than 1V Approx. 0.5V Approx. 0.6V Connect DC V B26 B39
B27 B27 TPS & Cam
Position
Sensor +5V
Supply GRN Less than 1V Approx. 5V Connect DC V B27 B39
B28 B28 Camshaft
Position (CMP)
Sensor Signal BLU - - Wave form - - - -
B29 B29 Inhibitor Switch
(AT Only) BLK Less than 1V P or N range: Less than 1V
Other than P or N range: 10-14V Connect DC V B29 GND
B30 B30 Power Steering
Pressure
Switch GRN/
YELLess than 1V Pressure switch is turned on: Less than 1V
Pressure Switch is turned off: 10-14V Connect DC V B30 GND
B31 B31 A/C Thermo
Relay GRN/
BLKLess than 1V A/C request is activated: 10-14V
A/C request is not activated: Less than 1VConnect DC V B31 GND

6E-48 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Signal or Continuity Tester Position Pin
No. B/Box
No. Pin Function Wire
Color
Key SW Off Key SW On Engine IdleEngine
2000rpm ECM
Connection Range (+) (-)
B32 B32 Vehicle Speed
Signal
(Immobilizer
Control Unit
Terminal B8) WHT - - Wave form or approx. 6.5V at
20km/h Connect AC V B32 GND
B33 B33 Ignition Switch BLU/
YELLess than 1V 10-14V Connect DC V B33 GND
B34 B34 Back Up
Power Supply RED/
WHT 10-14V Connect DC V B34 GND
B35 B35 No Connection - - - - - - - - -
B36 B36 ECM Main
Relay RED/
BLUWhile main
relay is
activated:
10-14V
Main relay is
not activated:
Less than 1V 10-14V Connect DC V B36 GND
B37 B37 ECM Main
Relay RED/
BLUWhile main
relay is
activated:
10-14V
Main relay is
not activated:
Less than 1V 10-14V Connect DC V B37 GND
B38 B38 To Data Link
Connect to No.
2 GRN - - - - - - - -
B39 B39 TPS, MAF, IAT
& CMP Sensor
Ground RED Continuity
with ground - - - Connect Ohm B39 GND
B40 B40 No Connection - - - - - - - - -

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-51

GENERAL DESCRIPTION FOR ECM AND
SENSORS
Engine Control Module (ECM)


1 2
(1) A Port
(2) B Port


The engine control module (ECM) is located on the
common chamber. The ECM controls the following.

Fuel metering system

Ignition timing

On-board diagnostics for powertrain functions.

The ECM constantly observes the information from
various sensors. The ECM controls the systems tha
t
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

Exhaust oxygen content

Mass air flow

Intake air temperature

Engine coolant temperature

Crankshaft position

Camshaft position

Throttle position

Vehicle speed

Power steering pressure

Air conditioning request on or off

EGR valve position

Outputs (Systems controlled):

Ignition control

Fuel control

Idle air control

Fuel pump

EVAP canister purge

Air conditioning

Diagnostics functions

The vehicle with automatic transmission, the
interchange of data between the engine control module
(ECM) and the transmission control module (TCM) is
performed via a CAN-bus system.
The following signals are exchanged via the CAN-bus:

ECM to TCM:

ECM CAN signal status

Engine torque

Coolant temperature

Throttle position

Engine speed

A/C status

CAN valid counter

TCM to ECM:

Ignition timing retard request

Garage shift status

CAN valid counter

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-53
Idle Air Control (IAC) Valve








Step
CoilAB CD
Coil A High
(EC M B13)On On
Coil A Low
(EC M B16)On On
Coil B High
(EC M B14)On On
Coil B Low
(EC M B17)On On

(IAC Valve Close Direction)
(IAC Valve Open Direction)



The idle air control valve (IAC) valve is two directional
and gives 2-way control. It has a stepping moto
r
capable of 256 steps, and also has 2 coils. With power
supply to the coils controlled steps by the engine control
module (ECM), the IAC valve's pintle is moved to adjus
t
idle speed, raising it for fast idle when cold or there is
extra load from the air conditioning or power steering.
By moving the pintle in (to decrease air flow) or out (to
increase air flow), a controlled amount of the air can
move around the throttle plate. If the engine speed is
too low, the engine control module (ECM) will retract the
IAC pintle, resulting in more air moving past the throttle
plate to increase the engine speed.
If the engine speed is too high, the engine control
module (ECM) will extend the IAC pintle, allowing less
air to move past the throttle plate, decreasing the
engine speed.

The IAC pintle valve moves in small step called counts.
During idle, the proper position of the IAC pintle is
calculated by the engine control module (ECM) based
on battery voltage, coolant temperature, engine load,
and engine speed.
If the engine speed drops below a specified value, and
the throttle plate is closed, the engine control module
(ECM) senses a near-stall condition. The engine control
module (ECM) will then calculate a new IAC pintle valve
position to prevent stalls. If the IAC valve is disconnected and reconnected with
the engine running, the idle speed will be wrong. In this
case, the IAC must be reset. The IAC resets when the
key is cycled "On" then "Off". When servicing the IAC, i
t
should only be disconnected or connected with the
ignition "Off".
The position of the IAC pintle valve affects engine start-
up and the idle characteristic of the vehicle.
If the IAC pintle is fully open, too much air will be
allowed into the manifold. This results in high idle
speed, along with possible hard starting and lean
air/fuel ratio.

Camshaft Position (CMP) Sensor








12
(1) Camshaft Position (CMP) Sensor
(2) EGR Valve


With the use of sequential multi-point fuel injection, a
hall element type camshaft position (CMP) is adopted to
provide information to be used in making decisions on
injection timing to each cylinder. It is mounted on the
rear of the left-hand cylinder head and sends signals to
the ECM.
One pulse is generated per two rotations of crankshaft.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-57
Starting Mode
When the ignition is first turned "ON," the ECM
energizes the fuel pump relay for two seconds to allo
w
the fuel pump to build up pressure. The ECM then
checks the engine coolant temperature (ECT) senso
r
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.

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

Camshaft position (CMP) sensor

Idle air control valve

Fuel pump

Fuel Injector
The sequential multi-port 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. Excess 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 separate.
If the pressure is too low, poor performance and a DTC
P0131, P0151, P0171, P0174, P1171 or P1174 will be
the result. If the pressure is too high, excessive odo
r
and/or a DTC P0132, P0152, P0172 or P0175 will be
the result. Refer to Fuel System Diagnosisfo
r
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 regulato
r
maintains a constant fuel pressure at the injectors.
Remaining fuel is then returned to the fuel tank.







055RV009
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 58 X 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 enough
pressure will result in poor performance.

Camshaft Position (CMP) Sensor Signal
The ECM uses this signal to determine the position o
f
the number 1 piston during its power stroke, allowing
the ECM to calculate true sequential multiport fuel
injection. Loss of this signal will set a DTC P0341. If the
CMP signal is lost while the engine is running, the fuel
injection system will shift to a calculated sequential fuel
injection based on the last fuel injection pulse, and the
engine will continue to run. The engine can be restarted
and will run in the calculated sequential mode as long
as the fault is present, with a 1-in-6 chance of being
correct.

6E-58 3.5L ENGINE DRIVEABILITY AND EMISSIONS
GENERAL DESCRIPTION FOR
ELECTRONIC IGNITION SYSTEM IGNITION
COILS & CONTROL
A separate coil-at-plug module is located at each spark
plug.
The coil-at-plug module is attached to the engine with
two screws. It is installed directly to the spark plug by an
electrical contact inside a rubber boot.
A three way connector provides 12 volts primary supply
from the ignition coil fuse, a ground switching trigge
r
line from the ECM, and ground.
The ignition control spark timing is the ECM's method o
f
controlling the spark advance and the ignition dwell.
The ignition control spark advance and the ignition dwell
are calculated by the ECM using the following inputs.

Engine speed

Crankshaft position (CKP) sensor

Camshaft position (CMP) sensor

Engine coolant temperature (ECT) sensor

Throttle position sensor

Park or neutral position switch

Vehicle speed sensor

ECM and ignition system supply voltage

Based on these sensor signal and engine load
information, the ECM sends 5V to each ignition coil
requiring ignition. This signal sets in the powe
r
transistor of the ignition coil to establish a grounding
circuit for the primary coil, applying battery voltage to
the primary coil.
At the ignition timing, the ECM stops sending the 5V
signal voltage. Under this condition the power transistor
of the ignition coil is set off to cut the battery voltage to
the primary coil, thereby causing a magnetic field
generated in the primary coil to collapse.
On this moment a line of magnetic force flows to the
secondary coil, and when this magnetic line crosses the
coil, high voltage induced by the secondary ignition
circuit to flow through the spark plug to the ground.

Ignition Control ECM Output
The ECM provides a zero volt (actually about 100 mV to
200 mV) or a 5-volt output signal to the ignition control
(IC) module. Each spark plug has its own primary and
secondary coil module ("coil-at-plug") located at the
spark plug itself. When the ignition coil receives the
5-volt signal from the ECM, it provides a ground path fo
r
the B+ supply to the primary side of the coil-at -plug
module. This energizes the primary coil and creates a
magnetic field in the coil-at-plug module. When the
ECM shuts off the 5-volt signal to the ignition control
module, the ground path for the primary coil is broken.
The magnetic field collapses and induces a high voltage
secondary impulse which fires the spark plug and
ignites the air/fuel mixture.
The circuit between the ECM and the ignition coil is
monitored for open circuits, shorts to voltage, and
shorts to ground. If the ECM detects one of these
events, it will set one of the following DTCs:

P0351: Ignition coil Fault on Cylinder #1

P0352: Ignition coil Fault on Cylinder #2

P0353: Ignition coil Fault on Cylinder #3

P0354: Ignition coil Fault on Cylinder #4

P0355: Ignition coil Fault on Cylinder #5

P0356: Ignition coil Fault on Cylinder #6

Spark Plug
Although worn or dirty spark plugs may give satisfactory
operation at idling speed, they frequency fail at highe
r
engine speeds. Faulty spark plugs may cause poor fuel
economy, power loss, loss of speed, hard starting and
generally poor engine performance. Follow the
scheduled maintenance service recommendations to
ensure satisfactory spark plug performance. Refer to
Maintenance and Lubrication.
Normal spark plug operation will result in brown to
grayish-tan deposits appearing on the insulator portion
of the spark plug. A small amount of red-brown, yellow,
and white powdery material may also be present on the
insulator tip around the center electrode. These
deposits are normal combustion by-products of fuels
and lubricating oils with additives. Some electrode wea
r
will also occur. Engines which are not running properly
are often referred to as “misfiring." This means the
ignition spark is not igniting the air/fuel mixture at the
proper time.
Spark plugs may also misfire due to fouling, excessive
gap, or a cracked or broken insulator. If misfiring
occurs before the recommended replacement interval,
locate and correct the cause.

6E-64 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Thought Process
As you follow a diagnostic plan, every box on the
Strategy Based Diagnostics chart requires you to use
the diagnostic thought process. This method of thinking
optimizes your diagnosis in the following ways:

Improves your understanding and definition of the
customer complaint

Saves time by avoiding testing and/or replacing
good parts


Allows you to look at the problem from different
perspectives

Guides you to determine what level o
f
understanding about system operation is needed:
 Owner’s manual level
 Service manual level
 In-depth (engineering) level
1. Verify the Complaint
What you should do
To verify the customer complaint, you need to know the
correct (normal) operating behavior of the system and
verify that the customer complaint is a valid failure o
f
the system.
The following information will help you verify the
complaint:

WHAT the vehicle model/options are

WHAT aftermarket and dealer-installed
accessories exist

WHAT related system(s) operate properly

WHEN the problem occurs

WHERE the problem occurs

HOW the problem occurs

HOW LONG the condition has existed (and if the
system ever worked correctly)

HOW OFTEN the problem occurs

Whether the severity of the problem has
increased, decreased or stayed the same
What resources you should use
Whenever possible, you should use the following
resources to assist you in verifying the complaint:
Service manual Theory or Circuit Description
sections

Service manual “System Performance Check”

Owner manual operational description

Technician experience

Identical vehicle for comparison


Circuit testing tools

Vehicle road tests

Complaint check sheet

Contact with the customer
2. Perform Preliminary Checks
NOTE: An estimated 10 percent of successful
vehicle repairs are diagnosed with this step!
What you should do
You perform preliminary checks for several reasons:

To detect if the cause of the complaint is
VISUALLY OBVIOUS

To identify parts of the system that work correctly

To accumulate enough data to correctly and
accurately search for a ISUZU Service Bulletin.
The initial checks may vary depending on the
complexity of the system and may include the following
actions:

Operate the suspect system

Make a visual inspection of harness routing and
accessible/visible power and ground circuits

Check for blown fuses

Make a visual inspection for separated connectors

Make a visual inspection of connectors (includes
checking terminals for damage and tightness)

Check for any DTCs stored by the on-board
computers

Sense unusual noises, smells, vibrations o
r
movements

Investigate the vehicle service history (call othe
r
dealerships, if appropriate)
What resources you should use
Whenever appropriate, you should use the following
resources for assistance in performing preliminary
checks:

Tech 2 or other technical equipment for viewing
DTCs

Service manual information:
 Component locations
 Harness routing
 Wiring schematics
 Procedures for viewing DTCs

Dealership service history file

Vehicle road test

Identical vehicle or system for comparison

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-65
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 related
to 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 experience 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 o
r
normally closed?
 Is the power switched or is the ground
switched?
 Is it a variable resistance circuit (ECT senso
r
or TPS, for example)?
 Is it a signal generating device (MAF senso
r
of VSS, for example)?