2004 ISUZU TF SERIES fuse

6E–104 ENGINE DRIVEABILITY AND EMISSIONS
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 alow it to stall.
4. Crank the engine for an additional 3 seconds.
Fuel Pressure Gauge Installation
1. Remove the fuel pressure fitting cap.
2. Install fuel pressure 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
1Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go 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?—Go to Fuel
System
DiagnosisGo 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.
Was the problem found?
—Verify repair Go to Step 5
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?
120 - 150
Go to Step 6Replace fuel
pump relay and
verify repair
11C56(J2)
F2 X2
Fuel Pump Relay

 




ENGINE DRIVEABILITY AND EMISSIONS 6E–105
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?
10 - 14.5V Go to Step 8Go 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?—Veri fy repai r—
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?
—Repair faulty
harness and
verify repair Go to Step 9
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?
10 - 14.5V Go to Step 11Go to Step 10 Step Action Value(s) Yes No
V
3
X2
4
11C56(J2) X2
V
1X2

ENGINE DRIVEABILITY AND EMISSIONS 6E–109
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 2 Scan Tool.
Following are applicable to the vehicle with
closed Loop System:
If an ex tremely lean condition occurs, the ox ygen
sensor(s) will stop toggling. The ox ygen 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 regulator
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 particular
fuel injector for fouling or saturation in order to
determine if that particular fuel injector is leaking. If
checking the spark plug associated with a particular
fuel injector for fouling or saturation does not
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 Fuel
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 20
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 45 to set. Driveability conditions associatedwith rich conditions can include hard starting
(followed by black smoke) and a strong sulfur smell
in the ex haust.
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 below
333 kPa (48 psi). A lean condition may cause a 44 to
set. Driveability conditions associated with lean
conditions can include hard starting (when the
engine is cold), hesitation, poor driveability, lack of
power, surging, and misfiring.
22.Restricting the fuel return line causes the fuel
pressure to rise above the regulated fuel pressure.
Command the fuel pump ON with the scan tool. 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. Located on the intake manifold which is at the top
right part of the engine.
3. Start the engine and allow it to stall.
4. Crank the engine for an additional 3 seconds.
Fuel Pressure Gauge Installation
1. Remove the fuel pressure fitting cap.
2. Install fuel pressure gauge 5-8840-0378-0 to the
fuel feed line located on the upper right side of the
engine.
3. Reinstall the fuel pump relay.

ENGINE DRIVEABILITY AND EMISSIONS 6E–165
7 Using the DVM and check the heater power supply
circuit for the affected cylinder.
1. Ignition “On”, engine “Off”.
2. Disconnect the O
2 sensor connector.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
10 - 14.5V Go to Step 9Go to Step 8
8 Repair the open or short to ground circuit between the
“O
2 Sensor” fuse (10A) and O2 sensor.
Is the action complete?—Veri fy repai r—
9 Using the DVM and check the heater ground circuit.
Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type A. (ECM
disconnected) Refer to 6E-88 page.
3. Disconnect the O
2 sensor connector.
4. Check the circuit for open or short to ground
circuit.
Was the problem found?
Breaker box is not available:
1. Ignition “Off”, engine “Off”.
2. Disconnect the O
2 sensor connector and ECM
connector.
3. Check the circuit for open or short to ground
circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 10 Step A ction Value(s) Yes No
4
V
E77
J2-31Breaker BoxE-77





331E56(J2) E77

6E–170 ENGINE DRIVEABILITY AND EMISSIONS
7 Using the DVM and check the injector power supply
circuit for the affected cylinder.
1. Ignition “On”, engine “Off”.
2. Disconnect the injector connector for the affected
cylinder.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
10 - 14.5V Go to Step 9Go to Step 8
8 Repair the open or short to ground circuit between the
“IGN” fuse (15A) and injector for the affected cylinder.
Is the action complete?—Veri fy repai r— Step A ction Value(s) Yes No
V
1
E-6 No.1 Cylinder
V
1
E-7 No.2 Cylinder
V
1
E-8 No.3 Cylinder
V
1
E-9 No.4 Cylinder

6E–190 ENGINE DRIVEABILITY AND EMISSIONS
8 Using the DVM and check the ignition coil module
power supply circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the ignition coil module connector.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
10 - 14.5V Go to Step 10Go to Step 9
9 Repair the open or short to ground circuit between the
“IGN. Coil” fuse (15A) and ignition coil module.
Is the action complete?—Veri fy repai r—
10 Replace the ignition coil module.
Was the problem solved?—Verify repair Go to Step 11
11 Is the ECM programmed with the latest software
release?
If not, download the latest software to the ECM using
the “SPS (Service Programming System)”.
Was the problem solved?—Verify repair Go to Step 12
12 Replace the ECM.
Is the action complete?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobilizer system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobilizer System-ECM replacement” for
the ECM/Immobilizer linking procedure.—Veri fy repai r— Step A ction Value(s) Yes No
V
E-18
2

ENGINE DRIVEABILITY AND EMISSIONS 6E–193
6 Using the DVM and check the purge solenoid valve
power supply circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the purge solenoid valve connector.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
10 - 14.5V Go to Step 8Go to Step 7
7 Repair the open or short to ground circuit between the
“Engine” fuse (15A) and purge solenoid valve.
Is the action complete?—Veri fy repai r -
8 Using the DVM and check the purge solenoid valve
solenoid signal circuit.
Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type A. (ECM
disconnected) Refer to 6E-88 page.
3. Disconnect the purge solenoid valve connector.
4. Check the circuit for open or short to ground
circuit.
Was the problem found?
Breaker box is not available:
1. Ignition “Off”, engine “Off”.
2. Disconnect the purge solenoid valve connector
and ECM connector.
3. Check the circuit for open or short to ground
circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 9 Step A ction Value(s) Yes No
V
E-66
2
J1-5Breaker BoxE-66




E-66 E-60(J1)
51

ENGINE DRIVEABILITY AND EMISSIONS 6E–195
DIAGNOSTIC TROUBLE CODE (DTC) P0502 VEHICLE SPEED SENSOR (VSS)
CIRCUIT LOW INPUT
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The vehicle speed sensor has a magnet rotated by the
transmission output shaft. Attached to the sensor is a
hall effect circuit that interacts with the magnetic field
created by the rotating magnet. A 12-volt operating
supply for the speed sensor hall circuit is supplied from
the meter fuse.
Diagnostic Aids
Poor connection at ECM: Inspect harness connectors
for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal to wire connection.
Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P0502 B Vehicle Speed Sensor Circuit Low
Input1. No DTC relating to MAP senso r, TPS, ECT
se nsor, inje ctor co ntrol circuit a nd ignitio n
co ntro l circuit.
2. Engine is running.
3. Vehicle spe ed is below 3km/h in po wer
condition or 2km/h in deceleration condi-
tion.ECM use s 0km/h co ndition a s substitute.