engine ISUZU TF SERIES 2004 Workshop Manual

6E–144 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
8 Using the DVM and check the vacuum pressure
sensor signal circuit.
1 . I g n i t i o n " O n " , e n g i n e " O f f " .
2. Disconnect the vacuum pressure sensor
connector.
3 . C h e c k t h e c i r c u i t f o r s h o r t t o p o w e r s u p p l y c i r c u i t .
Was the DVM indicated specified value?
Less than 1V Go to Step 9Repair faulty
harness and
verify repair
9 Substitute a known good vacuum pressure sensor
a n d re ch e c k.
Was the problem solved? - Go to Step 10Go to Step 11
10 Replace the vacuum pressure sensor.
Is the action complete? - Verify repair -
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
1 2 R e p l a c e t h e E C M .
I s t h e a c t i o n c o mp l e t e ?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobiliser system
(if equipped) must be linked to the ECM. Refer to
section 11 "Immobilizer System-ECM replacement" for
the ECM/Immobilizer linking procedure. - Verify repair - Step Action Value(s) Yes No
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4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–145
Diagnostic Trouble Code (DTC) P0105 (Symptom Code 2) (Flash Code 34)
Vacuum Pressure Sensor Circuit Low Input
Step Action 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 As Stored By ECU" in
"F0: Diagnostic Trouble Codes".
Is the DTC P0105 (Symptom Code 2) stored as
"Present Failure"? - Go to Step 3Refer to
Diagnostic Aids
and Go to Step
3
3 1. Using the Tech 2, ignition "On" and engine "Off".
2. Select "F1: Clear DTC Information" in "F0:
Diagnostic Trouble Codes" with the Tech 2 and
c l e a r t h e D T C i n f o r m a t i o n .
3. Operate the vehicle and monitor the "F0: Read
DTC Infor As Stored By ECU" in the "F0:
Diagnostic Trouble Codes".
Was the DTC P0105 (Symptom Code 2) 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 vacuum
pressure 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 V i s u a l l y c h e c k t h e v a c u u m p r e s s u r e s e n s o r .
Was the problem found? - Go to Step 9Go to Step 6
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6E–146 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
6 Using the DVM and check the vacuum pressure
sensor signal circuit.
Breaker box is available:
1 . I g n i t i o n " O f f " , e n g i n e " O f f " .
2. Install the breaker box as type A. (ECM
disconnected) Ref. Page 6E-103
3. Disconnect the vacuum pressure sensor
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 . I g n i t i o n " O f f " , e n g i n e " O f f " .
2. Disconnect the vacuum pressure sensor
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 7
7 Using the DVM and check the vacuum pressure
sensor power supply circuit.
1. Ignition "On", engine "Off".
2. Disconnect the vacuum pressure sensor
connector.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
Approx imately
5.0V
Go to Step 9Go to Step 8
85
Breaker BoxC-124





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4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–147
8 Repair the open circuit between the ECM and vacuum
p r e s s u r e s e n s o r.
Was the problem solved?
- Verify repair Go to Step 11
9 Substitute a known good vacuum pressure sensor
a s s e m b l y a n d r e c h e c k .
Was the problem solved? - Go to Step 10Go to Step 11
1 0 R e p l a c e t h e v a c u u m s e n s o r a s s e m b l y .
Is the action complete? - Verify repair -
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
1 2 R e p l a c e t h e E C M .
I s t h e a c t i o n c o mp l e t e ?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobiliser system
(if equipped) must be linked to the ECM. Refer to
section 11 "Immobilizer System-ECM replacement" for
the ECM/Immobilizer linking procedure. - Verify repair -
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6E–148 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0105 (Symptom Code 7) (Flash Code 34)
Vacuum Pressure Sensor Voltage Supply Circuit High Input
Step Action 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 As Stored By ECU" in
"F0: Diagnostic Trouble Codes".
Is the DTC P0105 (Symptom Code 7) stored as
"Present Failure"? - Go to Step 3Refer to
Diagnostic Aids
and Go to Step
3
3 1. Using the Tech 2, ignition "On" and engine "Off".
2. Select "F1: Clear DTC Information" in "F0:
Diagnostic Trouble Codes" with the Tech 2 and
c l e a r t h e D T C i n f o r m a t i o n .
3. Operate the vehicle and monitor the "F0: Read
DTC Infor As Stored By ECU" in the "F0:
Diagnostic Trouble Codes".
Was the DTC P0105 (Symptom Code 7) 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 vacuum
pressure 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 V i s u a l l y c h e c k t h e v a c u u m p r e s s u r e s e n s o r .
Was the problem found? - Go to Step 8Go to Step 6
6 Using the DVM and check the vacuum pressure
sensor power supply circuit.
1. Ignition "On", engine "Off".
2. Disconnect the vacuum pressure sensor
connector.
3. Check the circuit for short to battery voltage
circuit.
Was the DVM indicated specified value?
Approx imately
5.0V
Go to Step 8Go to Step 7
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4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–149
7 Repair the short to battery voltage circuit between the
ECM and vacuum pressure sensor.
Was the problem solved?
- Verify repair Go to Step 10
8 Substitute a known good vacuum pressure sensor
a s s e m b l y a n d r e c h e c k .
Was the problem solved? - Go to Step 9Go to Step 10
9 Replace the vacuum pressure sensor assembly.
Is the action complete? - Verify repair -
10 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 11
11 R e p l a c e t h e E C M .
I s t h e a c t i o n c o mp l e t e ?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobiliser system
(if equipped) must be linked to the ECM. Refer to
section 11 "Immobilizer System-ECM replacement" for
the ECM/Immobilizer linking procedure. - Verify repair -
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6E–150 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0105 (Symptom Code 9) (Flash Code 34)
Vacuum Pressure Sensor Voltage Supply Circuit Low Input
Step Action 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 As Stored By ECU" in
"F0: Diagnostic Trouble Codes".
Is the DTC P0105 (Symptom Code 9) stored as
"Present Failure"? - Go to Step 3Refer to
Diagnostic Aids
and Go to Step
3
3 1. Using the Tech 2, ignition "On" and engine "Off".
2. Select "F1: Clear DTC Information" in "F0:
Diagnostic Trouble Codes" with the Tech 2 and
c l e a r t h e D T C i n f o r m a t i o n .
3. Operate the vehicle and monitor the "F0: Read
DTC Infor As Stored By ECU" in the "F0:
Diagnostic Trouble Codes".
Was the DTC P0105 (Symptom Code 9) 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 vacuum
pressure 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 V i s u a l l y c h e c k t h e v a c u u m p r e s s u r e s e n s o r .
Was the problem found? - Go to Step 10Go to Step 6
6 Using the DVM and check the vacuum pressure
sensor power supply circuit.
1. Ignition "On", engine "Off".
2. Disconnect the vacuum pressure sensor
connector.
3 . C h e c k t h e c i r c u i t f o r s h o r t t o g r o u n d c i r c u i t .
Was the DVM indicated specified value?
Approx imately
5.0V
Go to Step 10Go to Step 7
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4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–151
7 Using the DVM and check the vacuum pressure
sensor power supply circuit.
1 . I g n i t i o n " O f f " , e n g i n e " O f f " .
2. Disconnect the vacuum pressure sensor
connector and ECM connector.
3. Check the circuit for short to vacuum pessure
sensor ground circuit.
Was the DVM indicated specified value?
No continuity Go to Step 9Go to Step 8
8 Repair the circuit for short to vacuum pressure sensor
ground.
Is the action complete? - Verify repair -
9 Repair the short to ground circuit between the vacuum
p r e s s u r e s e n s o r.
Was the problem solved? - Verify repair Go to Step 12
10 Substitute a known good MAF & IAT sensor assembly
a n d re ch e c k.
Was the problem solved? - Go to Step 11Go to Step 12
11 R e p l a c e t h e M A F & I A T s e n s o r a s s e m b l y .
Is the action complete? - Verify repair -
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 13
1 3 R e p l a c e t h e E C M .
I s t h e a c t i o n c o mp l e t e ?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobiliser system
(if equipped) must be linked to the ECM. Refer to
section 11 "Immobilizer System-ECM replacement" for
the ECM/Immobilizer linking procedure. - Verify repair -
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6E–152 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) P0110 (SYMPTOM CODE 1)
(FLASH CODE 23) INTAKE AIR TEMPERATURE (IAT) SENSOR CIRCUIT HIGH
INPUT
DIAGNOSTIC TROUBLE CODE (DTC) P0110 (SYMPTOM CODE 2)
(FLASH CODE 23) INTAKE AIR TEMPERATURE (IAT) SENSOR CIRCUIT LOW
INPUT
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The IAT sensor is a thermistor. A temperature changesthe resistance value. And it changes voltage. In other
words it measures a temperature value. Low air
temperature produces a high resistance.
Flash
CodeCode Symptom
CodeMIL DTC Name DTC Setting Condition Fail-Safe (Back Up)
23 P0110 1 ON Intake Air Temperature (IAT)
Se nsor Circuit High InputIAT sensor output voltage is
more than 4.7V.ECM use deg.C conditions as
substitute.
2 ON Intake Air Temperature (IAT)
Se nsor Circuit Low InputIAT sensor output voltage is
be lo w 0.3V.

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E –153
The ECM supplies 5 volts signal to the IAT sensor
through resisters in the ECM and measures the voltage.
The signal voltage will be high when the air temperature
is cold, and it will be low when the air temperature is
hot.
The output voltage ex cessively high or low, DTC P0110
(Symptom Code 1) or P0110 (Symptom Code 2) will be
stored.
Diagnostic Aids
An intermittent may be caused by the following:
 Poor connections. 
Misrouted harness.
 Rubbed through wire insulation.
 Broken wire inside the insulation.
Check for the following conditions:
 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.
 Damaged harness-Inspect the wiring harness for
damage. If the harness appears to be OK, observe
the “Intake Air Temperature ” display on the Tech2
while moving connectors and wiring harness related
to the sensor.
Diagnostic Trouble Code (DTC) P0110 (Sy mptom Code 1) (Flash Code 23)
Intake Air Temperature (IAT) Sensor Circuit High Input
Step Action Value(s) Yes No
1Was the “On-Board Diagnostic (OBD) System Check ”
performed?
— Go to Step 2 Go 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 As Stored By ECU ” in
“ F0: Diagnostic Trouble Codes ”.
Is the DTC P0110 (Symptom Code 1) stored as
“ Present Failure ”? —Go to Step 3 Refer to
Diagnostic Aids and Go to Step
3
3 1. Using the Tech 2, ignition “On ” and engine “Off ”.
2. Select “F1: Clear DTC Information ” in “F0:
Diagnostic Trouble Codes ” with the Tech 2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F0: Read
DTC Infor As Stored By ECU ” in the “F0:
Diagnostic Trouble Codes ”.
Was the DTC P0110 (Symptom Code 1) stored in this
ignition cycle? —Go to Step 4 Refer to
Diagnostic Aids and Go to Step
4
4 Check for poor/faulty connection at the IAT 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 Visually check the IAT sensor. Was the problem found? —Go to Step 12 Go to Step 6
92
84
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