ISUZU TF SERIES 2004 Workshop Manual

ENGINE DRIVEABILITY AND EMISSIONS 6E–145
7 Using the DVM and check the TPS power supply
circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the TPS connector.
3. Check the circuit for open or short to ground
circuit.
Was the DVM indicated specified value?
Approx imately
5.0V Go to Step 9Go to Step 8
8 Repair the open or short to ground circuit between the
ECM and TPS.
Was the problem solved?
—Verify repair Go to Step 12 Step A ction Value(s) Yes No
V
E68
2
2E60(J1) E68
15

6E–146 ENGINE DRIVEABILITY AND EMISSIONS
9 Using the DVM and check the TPS 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 TPS connector.
4. Check the circuit for open, short to sensor ground
or short to ground circuit.
Was the problem found?
Breaker box is not available:
1. Ignition “Off”, engine “Off”.
2. Disconnect the TPS connector and ECM
connector.
3. Check the circuit for open, short to sensor ground
or short to ground circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 12
10 Substitute a known good TPS and recheck.
Was the problem solved?—Go to Step 11Go to Step 12
11 Replace the TPS.
Is the action complete?—Veri fy repai r -
12 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
13 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
J1-7J1-32


Breaker BoxE-86









32 73E60(J1) E68

ENGINE DRIVEABILITY AND EMISSIONS 6E–147
DIAGNOSTIC TROUBLE CODE (DTC) P0123 THROTTLE POSITION SENSOR
HIGH INPUT
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The throttle position sensor circuit provides a voltage
signal that changes relative to throttle blade angle. The
signal voltage will vary from below 1 volt at closed
throttle to about 4 volts at wide open throttle (WOT).
The TPS is used by the engine control module (ECM)
for fuel control and most of the ECM-controlled outputs.
If the ECM detect a continuous short voltage in the TPS
or circuit, then a code P0123 will set.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM - Inspect harnessconnectors for backed-out terminals, improper
mating, broken locks, improperly formed or damaged
terminals, and poor terminal-to-wire connection.
If these codes are also set, it could indicate a
problem with the 5 Volt reference circuit or
components itself.
Damaged harness - Inspect the wiring harness for
damage, short to ground, short to battery positive and
open circuit. If the harness appears to be OK,
observe the Throttle Position sensor display on the
Tech 2 while moving connectors and wiring
harnesses related to the TP sensor. A change in the
display will indicate the location of the fault.
Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P0123 A Throttle Po sition Se nsor High Input TPS output v olta ge is mo re tha n 4.9V. The ECM uses 0% co nditio n as substitute.

6E–148 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0123 Throttle Position Sensor High Input
Step A ction Value(s) Yes No
1 Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go to On Board
Diagnostic
(OBD) System
Check
2 1. Connect the Tech 2.
2. Review and record the failure information.
3. Select “F0: Read DTC Infor By Priority” in “F0:
Diagnostic Trouble Code”.
Is the DTC P0123 stored as “Present Failure”?—Go to Step 3Refer to
Diagnostic Aids
and Go to Step
3
3 1. Using the Tech2, ignition “On” and engine “Off”.
2. Select “Clear DTC Information” with the Tech2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F5: Failed
This Ignition” in “F2: DTC Information”.
Was the DTC P0123 stored in this ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 Check for poor/faulty connection at the TPS or ECM
connector. If a poor/faulty connection is found, repair
as necessary.
Was the problem found?
—Verify repair Go to Step 5
5 Visually check the TPS.
Was the problem found? —Go to Step 12Go to Step 6
6 Using the DVM and check the TPS.
1. Ignition “Off”, engine “Off”.
2. Disconnect TPS connector.
3. Measure the resistance of TPS.
Does the tester indicate standard resistance as shown
in the following table?
Standard
resistance Go to Step 7Go to Step 12
E60(J1) E68
32 15
7
Measurement
Te r m i n a lRe sista nce (
)
1 - 2 Approximately 5.6k
a t idle po sitio n &
WO T
2 - 3 Approximately 6.0k
a t idle po sitio n
Approximately 1.7k
at WOT
1 - 3 Approximately 2.3k
a t idle po sitio n &
WO T
Approximately 6.6k
at WOT
21
3
TPS

ENGINE DRIVEABILITY AND EMISSIONS 6E–149
7 Using the DVM and check the TPS power supply
circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the TPS connector.
3. Check the circuit for short to voltage circuit.
Was the DVM indicated specified value?
Approx imately
5.0V Go to Step 9Go to Step 8
8 Repair the short to voltage circuit between the ECM
and TPS.
Was the problem solved?
—Verify repair Go to Step 14
9 Using the DVM and check the TPS signal circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the TPS connector.
3. Check the circuit for short to power supply circuit.
Was the DVM indicated specified value?
Less than 1V Go to Step 10Repair faulty
harness and
verify repair
10 Using the DVM and check the TPS ground circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the TPS connector .
3. Check the circuit for short to power supply circuit.
Was the DVM indicated specified value?
Less than 1V Go to Step 11Repair faulty
harness and
verify repair Step A ction Value(s) Yes No
V
E68
2
2E60(J1) E68
15
3
V
E68
1
V
E68

6E–150 ENGINE DRIVEABILITY AND EMISSIONS
11 Using the DVM and check the TPS 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 TPS connector.
4. Check the circuit for open circuit.
Was the problem found?
Breaker box is not available:
1. Ignition “Off”, engine “Off”.
2. Disconnect the TPS connector and ECM
connector.
3. Check the circuit for open circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 14
12 Substitute a known good TPS and recheck.
Was the problem solved?—Go to Step 13Go to Step 14
13 Replace the TPS.
Is the action complete?—Veri fy repai r—
14 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 14
15 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
J1-32Breaker BoxE-86








321E60(J1) E68

ENGINE DRIVEABILITY AND EMISSIONS 6E–151
DIAGNOSTIC TROUBLE CODE (DTC) P0131 O2 SENSOR CIRCUIT LOW
VOLTAGE (BANK 1 SENSOR 1)
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The engine control module (ECM) supplies a bias
voltage of about 450 mV between the heated ox ygen
sensor (HO2S) signal and low circuits. The ox ygen
sensor varies the voltage within a range of about 1000
mV when the ex haust is rich, down through about 10
mV when ex haust is lean. The ECM constantly monitors
the HO2S signal during “Closed Loop” operation and
compensates for a rich or lean condition by decreasing
or increasing injector pulse width as necessary. If theBank 1 HO2S 1 voltage remains ex cessively low for an
ex tended period of time, Diagnostic Trouble Code
P0131 will be set.
Diagnostic Aids
Check for the following conditions:
Heated oxygen sensor wiring - The sensor pigtail
may be routed incorrectly and/or contacting the
exhaust system. Also, check for shorts to ground,
shorts to battery positive and open circuits.
Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P0131 A O
2 SensorCircuit Low Voltage (Bank 1
Se nsor 1)1. No DTC re lating to MAP senso r, TPS,
EVAP purge, ECT sensor, CKP sensor,
VSS, injecto r contro l circuit and ignitio n
co ntro l circuit.
2. Engine coolant temperature is more than
60 de g. C.
3. O
2 sensor bank 1 output voltage is below
50mV in “Closed Loop” condition. “Ope n Lo op” fuel control.

6E–152 ENGINE DRIVEABILITY AND EMISSIONS
Poor ECM to engine block grounds.
Fuel pressure - The system will go lean if pressure is
too low. The ECM can compensate for some
decrease. However, if fuel pressure is too low, a
Diagnostic Trouble Code P0131 may be set. Refer to
Fuel System Diagnosis.
Lean injector(s) - Perform “I njector Balance Test.”
Vacuum leaks - Check for disconnected or damaged
vacuum hoses and for vacuum leaks at the intake
manifold, throttle body, EGR system, and PCV
system.Ex haust leaks - An ex haust leak may cause outside
air to be pulled into the ex haust gas stream past the
HO2S, causing the system to appear lean. Check for
exhaust leaks that may cause a false lean condition
to be indicated.
Fuel contamination - Water, even in small amounts,
can be delivered to the fuel injectors. The water can
cause a lean ex haust to be indicated. Ex cessive
alcohol in the fuel can also cause this condition. For
the procedure to check for fuel contamination, Refer
to Fuel System Diagnosis.
Diagnostic Trouble Code (DTC) P0131
O
2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
Step A ction Value(s) Yes No
1 Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go to On Board
Diagnostic
(OBD) System
Check
2 1. Connect the Tech 2.
2. Review and record the failure information.
3. Select “F0: Read DTC Infor By Priority” in “F0:
Diagnostic Trouble Code”.
Is the DTC P0131 stored as “Present Failure”?—Go to Step 3Refer to
Diagnostic Aids
and Go to Step
3
3 1. Using the Tech2, ignition “On” and engine “Off”.
2. Select “Clear DTC Information” with the Tech2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F5: Failed
This Ignition” in “F2: DTC Information”.
Was the DTC P0131 stored in this ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 Check for poor/faulty connection at the O
2 sensor 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 O
2 sensor circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the O
2 sensor connector.
3. Check the circuit for short to heater ground or
ground circuit.
Was the DVM indicated specified value?
Approximatly
450mV Go to Step 7Go to Step 6
C56(J2) E77
31 216
V
2 1
E77

ENGINE DRIVEABILITY AND EMISSIONS 6E–153
6 Using the DVM and check the O2 sensor 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.
4. Check the circuit for short to heater ground 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 short to heater ground or
short to ground circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 15
7 Using the DVM and check the O
2 sensor circuit.
1. Ignition “Off”, engine “Off”.
2. Disconnect the the O
2 sensor connector.
3. Check the circuit for short to heater ground circuit.
Was the DVM indicated specified value?
No continuity Go to Step 9Go to Step 8
8 Repair the short to heater ground circuit.
Was the problem found?—Verify repair Go to Step 15 Step A ction Value(s) Yes No
J2-6J2-21 Breaker BoxJ2-31






C-56(J2)



C-56(J2)




O2 Sensor










6E–154 ENGINE DRIVEABILITY AND EMISSIONS
9 1. Using the Tech 2, ignition “On” and engine “On”.
2. Monitor the “Manifold Absolute Pressure” in the
data display.
Does the Tech 2 indicate correct “Manifold Absolute
Pressure” in accordance with engine speed or
acceleration? —Go to Step 11Go to Step 10
10 Remove the MAP sensor and check for the following
conditions.
Objects blocking the air cleaner.
Objects blocking the MAP sensor.
Objects blocking the throttle valve.
Vacuum leaking at intake duct.
Vacuum leaking at throttle body.
If a problem is found, repair as necessary.
Was the problem found?—Verify repair Go to Step 11
11 1. Using the Tech 2, ignition “On” and engine “On”.
2. Select the “Miscellaneous Test” and perform the
“IAC Control” in the “IAC System”.
3. Operate the Tech 2 in accordance with procedure.
Was the engine speed changed, when the IAC valve
is operating step by step?—Go to Step 13Go to Step 12
12 Check for the following conditions.
Objects blocking the IAC valve.
Objects blocking the throttle valve.
Vacuum leaking at throttle body.
If a problem is found, repair as necessary.
Was the problem found?—Verify repair Go to Step 13
13 Check for injector for the affected bank.
Refer to “Injector Coil Test & Injector Balance Test
Procedure” 6E-98 page.
Was the injector operation correct?
—Go to Step 14Refer to Injector
Coil Test &
Injector
Balance Test
Procedure
14 Check for fuel pressure.
Refer to “Fuel System Diagnosis” 6E-108 page.
Was the fuel pressure correct? —Go to Step 15Refer to Fuel
System
Diagnosis
15 Replace the O
2 sensor.
Was the problem solved?—Verify repair Go to Step 16
16 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 17
17 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