2004 ISUZU TF SERIES relay

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E -83

MISCELLANEOUS TEST
The state of each circuit can be tested by using
miscellaneous test menus. Especially when DTC cannot
be detected, a faulty circuit can be diagnosed by testing
each circuit by means of these menus.
Even DTC has been detected, the circuit tests using
these menus could help discriminate between a
mechanical trouble and an electrical trouble.
Connect Tech 2 and select "Powertrain", "3.5L V6 6VE1
Hitachi" & "Miscellaneous Test".

F0: Lamps
F0: Malfunction Indicator Lamp
When the Tech 2 is operated, "Malfunction Indicato
r
Lamp (Check Engine Lamp)" is turned on or off.
The circuit is normal if the "Malfunction Indicator Lamp
(Check Engine Lamp)" in the instrument panel is turned
on or off in accordance with this operation.

F1: Relays
F0: Fuel Pump Relay
When the Tech 2 is operated, fuel pump relay signal
turns ON or OFF.
The circuit is normal if fuel pump sound is generated in
accordance with this operation when key switch is
turned ON.

"F1: A/C Clutch Relay"
When the Tech 2 is operated, A/C clutch relay signal
turns ON or OFF.
The circuit is normal if A/C compressor clutch is
energized in accordance with this operation when the
engine is running.

F2: EVAP
F0: Purge Solenoid
When the Tech 2 is operated, duty ratio of EVAP purge
solenoid is changed 10%-by-10%.

Purge Solenoid
Engine Speed 800 RPM
Desired Idle Speed 762 RPM
Engine Coolant Temperature 80

C
Start Up ECT 50

C
Intake Air Temperature 30

C
Throttle Position 0 %
EVAP Purge Solenoid 10 %



Press "Increase" key.

Then, EVAP Purge Solenoid increases

10%-by-10%.


Press "Quit" Key.

F3: IAC System
F0: RPM Control
When the Tech 2 is operated, "Desired Idle Speed"
increases 50rpm-by-50rpm up to 1550rpm.
The circuit is normal if engine speed is changed in
accordance with this operation.
RPM Control
Engine Speed 850 RPM
Desired Idle Speed 850 RPM
Engine Coolant Temperature 80

C
Start Up ECT 50

C
Intake Air Temperature 30

C
Throttle Position 0 %
Desired Idle Speed 850 RPM



Press "Increase" key.

Then, Desired Idle speed increases

50rpm-by-50rpm up to 1550rpm. Engine speed is
also changed by this operation.


Press "Quit" Key.

F0: IAC Control
When the Tech 2 is operated, "Idle Air Control"
increases or decreases 10steps-by-10steps up to
160steps.
The circuit is normal if idle engine speed is changed in
accordance with this operation.
IAC Control
Engine Speed 875 RPM
Desired Idle Speed 762 RPM
Engine Coolant Temperature 80

Start Up ECT 50

Intake Air Temperature 30

Throttle Position 0 %
Idle Air Control 30 Steps



Press "Increase" key.

Then, Idle Air Control increases 10steps-by-
10steps up to 160steps.

Engine speed is also changed by this operation.


Press "Quit" Key.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-111
FUEL SYSTEM ELECTRICAL TEST




RTW36ELF000101
CIRCUIT DESCRIPTION
When the ignition switch is first turned “ON," the Engine
Control Module (ECM) energizes the fuel pump relay
which applies power to the in-tank fuel pump. The fuel
pump relay will remain “ON" as long as the engine is
running or cranking and the ECM is receiving 58X
crankshaft position pulses. If no 58X crankshaft position
pulses are present, the ECM de-energizes the fuel
pump relay within 2 seconds after the ignition is turned
“ON" or the engine is stopped.
The fuel pump delivers fuel to the fuel rail and injectors,
then to the fuel pressure regulator. The fuel pressure
regulator controls fuel pressure by allowing excess fuel
to be returned to the fuel tank. With the engine stopped
and ignition “ON," the fuel pump can be turned “ON" by
using a command by the Tech 2.
DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection,
rubbed-through wire insulation, or a wire broken inside
the insulation. Check for the following items:
 Poor connection or damaged harness –Inspect the
ECM harness and connectors for improper mating,
broken locks, improperly formed or damaged
terminals, poor terminal-to-wire connection, and
damaged harness.

6E-112 3.5L ENGINE DRIVEABILITY AND EMISSIONS
CAUTION: To reduce the risk of fire and personal
injury:
 It is necessary to relieve fuel system pressure
before connecting a fuel pressure gauge. Refer to
Fuel Pressure Relief Procedure, below.
 A small amount of fuel may be released when
disconnecting the fuel lines. Cover fuel line
fittings with a shop towel before disconnecting,
to catch any fuel that may leak out. Place the
towel in an approved container when the
disconnect is completed.
FUEL PRESSURE RELIEF PROCEDURE
1. Remove the fuel cap.
2. Remove the fuel pump relay from the underhood
relay center.
3. Start the engine and allow it to stall.
4. Crank the engine for an additional 3 seconds.
FUEL GAUGE INSTALLATION
1. Remove the fuel pressure fitting cap.
2. Install fuel gauge 5-8840-0378-0 to the fuel feed line
located in front of and above the right side valve
cover.
3. Reinstall the fuel pump relay.

Fuel System Electrical Test
Step Action Value (s) Yes No
1
Was the "On-Board Diagnostic (OBD) System Check"
performed?
- Go to Step 2 Go to On Board
Diagnostic (OBD)
System Check
2
1. Using the Tech 2, ignition "On" and engine "On".
2. Select the "Miscellaneous Test" and perform the
"Fuel Pump Relay" in the "Relays".
3. Operate the Tech 2 in accordance with procedure.
Was the fuel pump operated, when the Tech 2 is
operated?
- Test completed Go to Step 3
3
Check the "Fuel Pump" fuse (20A). If the fuse is burnt
out, repair as necessary.
Was the problem found?
- Verify repair Go to Step 4
4
Check for poor/faulty connection at the fuel pump, fuel
pump relay or ECM connector. If a poor/faulty
connection is found, repair as necessary.
E-61(B)
X-2


F-2
C-109










Was the problem found?
- Verify repair Go to Step 5

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-113
Step Action Value (s) Yes No
5
Using the DVM and check the fuel pump relay.
1. Ignition "Off", engine "Off".
2. Remove the fuel pump relay from the relay box.
3. Check the relay coil.
Was the DVM indicated specified value?
X-2


1
3 2
4






Approximately
140

Go to Step 6 Replace fuel
pump relay and
verify repair
6
Using the DVM and check the fuel pump relay power
supply circuit.
1. Ignition "On", engine "Off".
2. Remove the fuel pump relay from the relay box.
3. Check the circuit for open or short to ground circuit.
Was the DVM indicated specified value?
X-2


V



10 – 14.5V Go to Step 8 Go to Step 7
7
Repair the open or short to ground circuit between the
"ECM" fuse (15A) and fuel pump relay.
Is the action complete?
- Verify repair -
8
Using the DVM and check the fuel pump relay ground
circuit.
1. Ignition "Off", engine "Off".
2. Disconnect the ECM connector.
3. Remove the fuel pump relay from the relay box.
4. Check the circuit for open or short to ground circuit.
Was the problem found?
E-61(B)
X-2









- Repair faulty
harness and
verify repair Go to Step 9

6E-114 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
9
Using the DVM and check the fuel pump relay power
supply circuit.
1. Ignition "Off", engine "Off".
2. Remove the fuel pump relay from the relay box.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
X-2

V



10 – 14.5V Go to Step 11 Go to Step 10
10
Repair the open circuit between the fuel pump relay
and battery.
Is the action complete?
- Verify repair -
11
Using the DVM and check the fuel pump power supply
circuit.
1. Ignition "On", engine "Off".
2. Disconnect the fuel pump connector.
3. Check the circuit for open or short to ground circuit.
Was the DVM indicated specified value?
F-2


V

10 – 14.5V Go to Step 13 Go to Step 12
12
Repair the open or short to ground circuit between the
fuel pump relay and fuel pump.
Is the action complete?
F-2
X-2





- Verify repair -

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-117
CIRCUIT DESCRIPTION
When the ignition switch is turned “ON," the Engine
Control Module (ECM) will turn “ON" the in-tank fuel
pump. The in-tank fuel pump will remain “ON" as long
as the engine is cranking or running and the ECM is
receiving 58X crankshaft position pulses. If there are no
58X crankshaft position pulses, the ECM will turn the
in-tank fuel pump “OFF" 2 seconds after the ignition
switch is turned “ON" or 2 seconds after the engine
stops running.
The in-tank fuel pump is an electric pump within an
integral reservoir. The in-tank fuel pump supplies fuel
through an in-line fuel filter to the fuel rail assembly. The
fuel pump is designed to provide fuel at a pressure
above the pressure needed by the fuel injectors. A fuel
pressure regulator, attached to the fuel rail, keeps the
fuel available to the fuel injectors at a regulated
pressure. Unused fuel is returned to the fuel tank by a
separate fuel return line.
TEST DESCRIPTION
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Connect the fuel pressure gauge to the fuel feed line
as shown in the fuel system illustration. Wrap a shop
towel around the fuel pressure connection in order to
absorb any fuel leakage that may occur when
installing the fuel pressure gauge. With the ignition
switch “ON" and the fuel pump running, the fuel
pressure indicated by the fuel pressure gauge
should be 333-376 kPa (3.4-3.8 kg/cm
2 / 48-55 psi).
This pressure is controlled by the amount o
f
pressure the spring inside the fuel pressure regulator
can provide.
3. A fuel system that cannot maintain a constant fuel
pressure has a leak in one or more of the following
areas:
 The fuel pump check valve.
 The fuel pump flex line.
 The valve or valve seat within the fuel pressure
regulator.
 The fuel injector(s).
4. Fuel pressure that drops off during acceleration,
cruise, or hard cornering may case a lean condition.
A lean condition can cause a loss of power, surging,
or misfire. A lean condition can be diagnosed using
a Tech 1 Tech 2. If an extremely lean condition
occurs, the oxygen sensor(s) will stop toggling. The
oxygen sensor output voltage(s) will drop below 500
mV. Also, the fuel injector pulse width will increase.

Important: Make sure the fuel system is not operating
in the “Fuel Cut-Off Mode."
When the engine is at idle, the manifold pressure is
low (high vacuum). This low pressure (high vacuum)
is applied to the fuel pressure regulator diaphragm.
The low pressure (high vacuum) will offset the
pressure being applied to the fuel pressure regulato
r
diaphragm by the spring inside the fuel pressure
regulator. When this happens, the result is lower fuel
pressure. The fuel pressure at idle will vary slightly
as the barometric pressure changes, but the fuel
pressure at idle should always be less than the fuel
pressure noted in step 2 with the engine “OFF."
16.Check the spark plug associated with a particula
r
fuel injector for fouling or saturation in order to
determine if that particular fuel injector is leaking. I
f
checking the spark plug associated with a particular
fuel injector for fouling or saturation does no
t
determine that a particular fuel injector is leaking,
use the following procedure:
 Remove the fuel rail, but leave the fuel lines and
injectors connected to the fuel rail. Refer to Fue
l
Rail Assembly in On-Vehicle Service.
 Lift the fuel rail just enough to leave the fuel
injector nozzles in the fuel injector ports.
CAUTION: In order to reduce the risk of fire and
personal injury that may result from fuel spraying
on the engine, verify that the fuel rail is positioned
over the fuel injector ports and verify that the fuel
injector retaining clips are intact.
 Pressurize the fuel system by connecting a 10
amp fused jumper between B+ and the fuel pump
relay connector.

Visually and physically inspect the fuel injector
nozzles for leaks.
17. A rich condition may result from the fuel pressure
being above 376 kPa (55 psi). A rich condition may
cause a DTC P0132 or a DTC P0172 to set.
Driveability conditions associated with rich conditions
can include hard starting (followed by black smoke)
and a strong sulfur smell in the exhaust.
20.This test determines if the high fuel pressure is due
to a restricted fuel return line or if the high fuel
pressure is due to a faulty fuel pressure regulator.
21.A lean condition may result from fuel pressure belo
w
333 kPa (48 psi). A lean condition may cause a DTC
P0131 or a DTC P0171 to set. Driveability conditions
associated with lean conditions can include hard
starting (when the engine is cold ), hesitation, poo
r
driveability, lack of power, surging , and misfiring.

6E-118 3.5L ENGINE DRIVEABILITY AND EMISSIONS
22.Restricting the fuel return line causes the fuel
pressure to rise above the regulated fuel pressure.
Command the fuel pump “ON" with the Tech 2. The
fuel pressure should rise above 376 kPa (55 psi) as
the fuel return line becomes partially closed.
NOTE: Do not allow the fuel pressure to exceed 414
kPa (60 psi). Fuel pressure in excess of 414 kPa (60
psi) may damage the fuel pressure regulator.
CAUTION: To reduce the risk of fire and personal
injury:
 It is necessary to relieve fuel system pressure
before connecting a fuel pressure gauge. Refer to
Fuel Pressure Relief Procedure, below.
 A small amount of fuel may be released when
disconnecting the fuel lines. Cover fuel line
fittings with a shop towel before disconnecting,
to catch any fuel that may leak out. Place the
towel in an approved container when the
disconnect is completed.
FUEL PRESSURE RELIEF PROCEDURE
1. Remove the fuel cap.
2. Remove the fuel pump relay from the underhood
relay center.
3. Start the engine and allow it to stall.
4. Crank the engine for an additional 3 seconds.
FUEL GAUGE INSTALLATION
1. Remove the fuel pressure fitting cap.
2. Install fuel gauge 5-8840-0378-0 to the fuel supply
line located in front of and above the right side valve
cover.
3. Reinstall the fuel pump relay.

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.