2004 ISUZU TF SERIES air conditioning

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-79
TYPICAL SCAN DATA & DEFINITIONS (ENGINE DATA)
Use the typical values table only after the On-Board Diagnostic System check has been completed, no DTC(s) were noted, and you have determined that the On-Board
Diagnostic are functioning properly.
Tech2 values from a properly running engine may be used for comparison with the engine you are diagnosing.
Condition : Vehicle stopping, engine running, air conditioning off & after warm-up (Coolant temperature approximately 80
C)

Tech 2
Parameter
Units Idle 2000rpm Definitions
1 Ignition Voltage V 10.0  14.5 10.0  14.5 This displays the system voltage measured by the ECM at ignition feed.
2 Engine Speed rpm 710  860 1950  2050 The actual engine speed is measured by ECM from the CKP sensor 58X signal.
3 Desired Idle
Speed rpm 750  770 750  770 The desired engine idle speed that the ECM commanding.
The ECM compensates for various engine loads.
4 Engine Coolant
Temperature
C or
F 80  90 (

) 80  90 (

) The ECT is measured by ECM from ECT sensor output voltage.
When the engine is normally warm upped, this data displays approximately 80 °C or
more.
5 Start Up ECT
(Engine Coolant
Temperature)
C or
F Depends on ECT
at start-up
Depends on ECT
at start-up
Start-up ECT is measured by ECM from ECT sensor output voltage when engine is
started.
6 Intake Air
Temperature

C or
F Depends on
ambient temp.
Depends on
ambient temp.
The IAT is measured by ECM from IAT sensor output voltage.
This data is changing by intake air temperature.
7 Throttle Position % 0 4  6 Throttle position operating angle is measured by the ECM from throttle position
output voltage.
This should display 0% at idle and 99  100% at full throttle.
8 Throttle Position
Sensor V 0.4  0.7 0.6  0.8 The TPS output voltage is displayed.
This data is changing by accelerator operating angle.
9 Mass Air Flow g/s 5.0  8.0 13.0  16.0 This displays intake air amount.
The mass air flow is measured by ECM from the MAF sensor output voltage.
10 Air Fuel Ratio 14.7:1 14.7:1 This displays the ECM commanded value.
In closed loop, this should normally be displayed around 14.2:1  14.7:1.
11 Idle Air Control Steps 10  20 20  30 This displays the ECM commanded position of the idle air control valve pintle.
A larger number means that more air is being commanded through the idle air
passage.
12 EGR Valve V 0.00 0.00  0.10 The EGR position sensor output voltage is displayed.
This data is changing by EGR valve solenoid operating position.
13 Desired EGR
Opening V 0.00 0.05  1.10 The ECM commanded EGR position sensor voltage is displayed.
According to the current position, ECM changes EGR valve solenoid operating
position to meet the desired position.
14 EGR Valve On
Duty % 0 32 – 38 This displays the duty signal from the ECM to control the EGR valve.
15 Engine Load % 2  7 8  15 This displays is calculated by the ECM form engine speed and MAF sensor reading.
Engine load should increase with an increase in engine speed or air flow amount.
16 B1 Fuel System
Status Open Loop/ Close
Loop Close Loop Close Loop
17 B2 Fuel System
Status Open Loop/ Close
Loop Close Loop Close Loop
When the engine is first started the system is in "Open Loop" operation.
In "Open Loop", the ECM ignores the signal from the oxygen sensors.
When various conditions (ECT, time from start, engine speed & oxygen 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
oxygen sensors.
18 Fuel Trim
Learned (Bank 1) Yes/No Yes Yes
19 Fuel Trim
Learned (Bank 2) Yes/No Yes Yes
When conditions are appropriate for enabling long term fuel trim corrections, fuel trim
learn will display "Yes".
This indicates that the long term fuel trim is responding to the short term fuel trim.
If the fuel trim lean displays "No", then long term fuel trim will not respond to changes
in short term fuel trim.
20 Injection Pulse
Bank 1 ms 2.0  4.0 2.0  4.0
21 Injection Pulse
Bank 2 ms 2.0  4.0 2.0  4.0
This displays the amount of time the ECM is commanding each injector On during
each engine cycle.
A longer injector pulse width will cause more fuel to be delivered. Injector pulse width
should increase with increased engine load.
22 Spark Advance °CA 10  15 35  42 This displays the amount of spark advance being commanded by the ECM.

6E-80 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Tech 2
Parameter
Units Idle 2000rpm Definitions
23 A/C Request (Air
Conditioning) On/Off Off Off This displays the air conditioner request signal. This should display "On" when the air
conditioner switch is switched on.
24 A/C Clutch On/Off Off Off This displays whether the ECM has commanded the A/C compressor clutch "On" or
"Off".
25 EVAP Purge
Solenoid
(Evaporative
Emission) % 50
80 0 This displays the duty signal from the ECM to control the canister purge solenoid
valve.
26 Fuel Trim Cell 49
52 13
17 This displays dependent on engine speed and MAF sensor reading.
A plot of engine speed versus MAF amount is divided into the cells.
Fuel trim cell indicates which cell is currently active.
27 Fuel Pump On/Off On On This displays operating status for the fuel pump main relay.
This should display "On" when the key switch is turned on and while engine is
running.
28 Deceleration Fuel
Cutoff Active/ Inactive Inactive Inactive The ECM will command the deceleration fuel mode when it detects a closed throttle
position while the vehicle is traveling.
While in decreasing fuel mode, the ECM will decrease the amount of fuel delivered
by entering open loop and decreasing the injector pulse width.
29 Power Enrichment Yes/No No No The ECM will command power enrichment mode "Yes" when a large increase in
throttle position and load is detected.
While in power enrichment mode, the ECM will increase the amount of fuel delivered
by entering open loop and increasing the injector pulse width.
30 Vehicle Speed km/h or mph 0 0 This displays vehicle speed.
The vehicle speed is measured by ECM from the vehicle speed sensor.
31 Cam Signal Present/ Missing Present Present This displays input signal from the camshaft position sensor.
When the correct pulse is generated, signal is received.
32 PSP Switch
(Power Steering
Pressure) Normal Pressure /
High Pressure Normal PressureNormal PressureThis displays the power steering pressure signal.
This should display "High Pressure" when the steering is steered.
33 Security Code
Status Programmable/
Not
Programmable Programmable Programmable This should display "Programmable" when the correct security code & secret code
are programmed.
34 Security Code Okay/ Not Okay Okay Okay This should display "Okay" when the security code is correctly accepted.
35 Immobilizer
System Normal /
Abnormal Normal Normal This should display "Normal" when the immobilizer is correctly operated.
36 Malfunction
Indicator Lamp On/Off Off Off This displays operating status for the Check Engine Lamp.
This should display "On" when the Check Engine Lamp is turned on.
37 Time From Start   This displays the engine time elapsed since the engine was started.
If the engine is stopped, engine run time will be reset to 00:00:00

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-81
TYPICAL SCAN DATA & DEFINITIONS (O2 SENSOR DATA)
Use the typical values table only after the On-Board Diagnostic System check has been completed, no DTC(s) were noted, and you have determined that the On-Board
Diagnostic are functioning properly.
Tech2 values from a properly running engine may be used for comparison with the engine you are diagnosing.
Condition : Vehicle stopping, engine running, air conditioning off & after warm-up (Coolant temperature approximately 80
C)

Tech 2
Parameter
Units Idle 2000rpm Definitions
1 Ignition Voltage V 10.0  14.5 10.0  14.5 This displays the system voltage measured by the ECM at ignition feed.
2 Engine Speed rpm 710  860 1950  2050 The actual engine speed is measured by ECM from the CKP sensor 58X signal.
3 Desired Idle
Speed rpm 750  770 750  770 The desired engine idle speed that the ECM commanding.
The ECM compensates for various engine loads.
4 Engine Coolant
Temperature
C or
F 80  90 (
C) 80  90 (
C) The ECT is measured by ECM from ECT sensor output voltage.
When the engine is normally warm upped, this data displays approximately 80 °C or
more.
5 Start Up ECT
(Engine Coolant
Temperature)
C or
F Depends on ECT
at start-up
Depends on ECT
at start-up
Start-up ECT is measured by ECM from ECT sensor output voltage when engine is
started.
6 Throttle Position % 0 4  6 Throttle position operating angle is measured by the ECM from throttle position
output voltage.
This should display 0% at idle and 99  100% at full throttle.
7 Throttle Position
Sensor V 0.4  0.7 0.6  0.8 The TPS output voltage is displayed.
This data is changing by accelerator operating angle.
8 Mass Air Flow g/s 5.0  8.0 13.0  16.0 This displays intake air amount.
The mass air flow is measured by ECM from the MAF sensor output voltage.
9 Air Fuel Ratio 14.7:1 14.7:1 This displays the ECM commanded value. In closed loop, this should normally be
displayed around 14.2:1  14.7:1.
10 Engine Load % 2  7 8  15 This displays is calculated by the ECM form engine speed and MAF sensor reading.
Engine load should increase with an increase in engine speed or air flow amount.
11 B1 Fuel System
Status Open Loop/ Close
Loop Close Loop Close Loop
12 B2 Fuel System
Status Open Loop/ Close
Loop Close Loop Close Loop
When the engine is first started the system is in "Open Loop" operation.
In "Open Loop", the ECM ignores the signal from the oxygen sensors.
When various conditions (ECT, time from start, engine speed & oxygen 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
oxygen sensors.
13 B1S1 O2 Sensor
(Bank1 Sensor 1)
mV 50  950 50 950
14 B2S1 O2 Sensor
(Bank2 Sensor 1)
mV 50  950 50  950
This displays the exhaust oxygen sensor output voltage.
Should fluctuate constantly within a range between 10mV (lean exhaust) and
1000mV (rich exhaust) while operating in closed loop.
15 B1 O2 Sensor
Ready (Bank 1)
Yes/No Yes Yes
16 B2 O2 Sensor
Ready (Bank 2)
Yes/No Yes Yes
This displays the status of the exhaust oxygen sensor.
This display will indicate "Yes" when the ECM detects a fluctuating oxygen sensor
output voltage sufficient to allow closed loop operation.
This will not occur unless the oxygen sensor is warmed up.
17 B1 Long Term
Fuel Trim (Bank
1)
% -10  20 -10  20
18 B2 Long Term
Fuel Trim (Bank
2)
% -10  20 -10  20
The long term fuel trim is delivered from the short term fuel term values and
represents a long term correction of fuel delivery for bank in question.
A value of 0% indicates that fuel delivery requires no compensation to maintain the
ECM commanded air fuel ratio.
A negative value indicates that the fuel system is rich and fuel delivery is being
reduced (decreased injector pulse width).
A positive value indicates that a lean condition exists and the ECM is compensating
by add fuel (increased injector pulse width).
Because long term fuel trim tends to follow short term fuel trim, a value in the
negative range due to canister purge at idle should not be considered unusual.
Excessive long term fuel trim values may indicate an rich or lean condition.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-119
Fuel System Diagnosis

Step Action Value(s) YES NO
1
Was the “On-Board Diagnostic (OBD) System Check"
performed? — Go to Step 2 Go to OBD
System Check
2
1. Turn the ignition “OFF."
2. Turn the air conditioning system “OFF."
3. Relieve fuel system pressure and install the fuel
pressure gauge.
Refer to 6E-118 FUEL GAUGE INSTALLATION
4. Turn the ignition “ON."
NOTE: The fuel pump will run for approximately 2
seconds. Use the Tech 2 to command the fuel
pump “ON".
5. Observe the fuel pressure indicated by the fuel
pressure gauge with the fuel pump running.
Is the fuel pressure within the specified limits? 290-376 kPa
(42-55 psi) Go to Step 3 Go to Step 17
3
The fuel pressure will drop when the fuel pump stops
running, then it should stabilize and remain constant.
Does the fuel pressure indicated by the fuel pressure
gauge remain constant? — Go to Step 4 Go to Step 12
4
1. When the vehicle is at normal operation
temperature, turn the ignition “ON" to build fuel
pressure and observe the measurement on the
gauge.
2. Start the engine and observe the fuel pressure
gauge.
Did the reading drop by the amount specified after the
engine was started? 21-105 kPa
(3-15 psi) Go to Step 5 Go to Step 9
5
Is fuel pressure dropping off during acceleration,
cruise, or hard cornering? — Go to Step 6 Check for
improper fuel
6 Visually and physically inspect the following items for
a restriction:
 The in-line fuel filter.
 The fuel feed line.
Was a restriction found? — Verify repair Go to Step 7
7 Remove the fuel tank and visually and physically
inspect the following items:
 The fuel pump strainer for a restriction.
 The fuel line for a leak.
 Verify that the correct fuel pump is in the vehicle.
Was a problem found in any of these areas? — Verify repair Go to Step 8

6E-122 3.5L ENGINE DRIVEABILITY AND EMISSIONS
A/C SYSTEM CIRCUIT DIAGNOSIS



RTW36EMF000101

CIRCUIT DESCRIPTION
When air conditioning and blower fan are selected, and
if the system has a sufficient refrigerant charge, a
12-volt signal is supplied to the A/C request input of the
Engine Control Module (ECM). The A/C request signal
may be temporarily canceled during system operation
by the electronic thermostat in the evaporator case. The
electronic thermostat may intermittently remove the
control circuit ground for the A/C thermostat relay to
prevent the evaporator from forming ice. When the A/C
request signal is received by the ECM, the ECM
supplies a ground from the compressor clutch relay i
f
the engine operating conditions are within acceptable
ranges. With the A/C compressor relay energized,
voltage is supplied to the compressor clutch coil.
The ECM will enable the compressor clutch to engage
whenever A/C has been selected with the engine
running, unless any of the following conditions are
present:

 The A/C request switch is "Off".
 The engine speed is lower than 550rpm or greate
r
than 6375rpm.
 The engine coolant temperature is greater than
120
.
DIAGNOSTIC AIDS
To diagnose an the intermittent fault, check for the
following conditions:
 Poor connection at the ECM–Inspect connections fo
r
backed-out terminals, improper mating, broken locks,
improperly formed or damaged terminals, and poo
r
terminal-to-wire connection.
 Damaged harness–Inspect the wiring harness fo
r
damage. If the harness appears to OK, observe the
A/C clutch while moving connectors and wiring
harnesses related to the A/C. A sudden clutch
malfunction will indicate the source of the intermitten
t
fault.

ENGINE ELECTRICAL 6D1-5











































Battery fluid is a highly corrosive acid.
Should battery fluid come in contact with your eyes, skin,
fabric, or a painted surface, immediately and thoroughly rinse
the affected area with clean tap water.
Never allow metal tools or jumper cables to come in contact
with the positive battery terminal, or any other metal surface of
the vahicle. This will protect against a short circuit.
Always keep batteries out of reach of young children.
Jump Starting Procedure
1. Set the vehicle parking brake.
If the vahicle is equipped with an automatic transmission,
place the selector level in the "PARK" position.
If the vehicle is equipped with a manual transmission, place
the shift lever in the "NEUTRAL" position.
Turn "OFF" the ignition.
Turn "OFF" all lights and any other accessory requiring
electrical power.
2. Look at the built-in hydrometer.
If the indication area of the built-in hydrometer is completely
clear, do not try to jump start.
3.
Attach the end of one jumper cable to the positive terminal
of the booster battery.

Attach the other end of the same cable to the positive
terminal of the discharged battery.
Do not allow the vehicles to touch each other. This will
cause a ground connection, effectively neutralizing the
charging procedure.
Be sure that the booster battery has a 12 volt rating.
4.
Attach one end of the remaining cable to the negative
terminal of the booster battery.

Attach the other end of the same cable to a solid engine
ground (such as the air conditioning compressor bracket o
r
the generator mounting bracket) of the vehicle with the
discharged battery.
The ground connection must be at least 450 mm (18 in.)
from the battery of the vehicle whose battery is being
charged.
WARNING: NEVER ATTACH THE END OF THE JUMPER
CABLE DIRECTLY TO THE NEGATIVE TERMINAL OF THE
DEAD BATTERY.
5. Start the engine of the vehicle with the good battery.
Make sure that all unnecessary electrical accessories have
been turned "OFF".
6. Start the engine of the vehicle with the dead battery.
7. To remove the jumper cables, follow the above directions in
reverse order.
Be sure to first disconnect the negative cable from the
vehicle with the discharged battery.