ISUZU TF SERIES 2004 Workshop Manual

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E –159
7 Using the DVM and check the IAT sensor signal
circuit.
Breaker box is available:
1. Ignition “Off ”, engine “Off ”.
2. Install the breaker box as type A. (ECM disconnected) Ref. Page 6E-103
3. Disconnect the MAF & IAT sensor connector.
4. Check the circuit for short to sensor ground or ground circuit.
Was the problem found?
Breaker box is not available: 1. Ignition “Off ”, engine “Off ”.
2. Disconnect the MAF & IAT sensor connector and ECM connector.
3. Check the circuit for short to sensor ground or ground circuit.
Was the problem found?
— Repair faulty
harness and verify repair Go to Step 10
8 Substitute a known good MAF & IAT sensor assembly and recheck.
Was the problem solved? —Go to Step 9 Go to Step 10
9 Replace the MAF & IAT 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 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. —Verify repair —
Step Action Value(s) Yes No
8492


Breaker Box


92
84
C-57(B)

6E–160 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) P0115 (SYMPTOM CODE 1)
(FLASH CODE 14) ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT
HIGH INPUT
DIAGNOSTIC TROUBLE CODE (DTC) P0115 (SYMPTOM CODE 2)
(FLASH CODE 14) ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT LOW
INPUT
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The ECT sensor is a thermistor. A temperature changesthe resistance value. And it changes voltage. In other
words it measures a temperature value. It is installed on
the coolant stream. Low coolant temperature produces
Flash
CodeCode Symptom
CodeMIL DTC Name DTC Setting Condition Fail-Safe (Back Up)
14 P0115 1 ON Engine Coolant Temperature
(ECT) Se nsor Circuit High
InputECT sensor output voltage is
more than 4.7V.1. ECM uses fue l te mpe rature
as substitute.
2. ECM uses 60 de g.C
condition for injection timing
contro l.
3. ECM uses -25 de g.C
condition (4JA1-TC) or -15
deg.C condition (4JH1-TC)
for glo w time co ntro l. 2 ON Engine Coolant Temperature
(ECT) Se nsor Circuit Low
InputECT sensor output voltage is
be lo w 0.3V.

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E –161
a high resistance.
The ECM supplies 5 volts signal to the ECT sensor
through resisters in the ECM and measures the voltage.
The signal voltage will be high when the engine
temperature is cold, and it will be low when the engine
temperature is hot.
The output voltage ex cessively high or low, DTC P0115
(Symptom Code 1) or P0115 (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 “Coolant Temperature ” display on the Tech2 while
moving connectors and wiring harness related to the
sensor.
Diagnostic Trouble Code (DTC) P0115 (Sy mptom Code 1) (Flash Code 14)
Engine Coolant Temperature 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 P0115 (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 P0115 (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 ECT 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 ECT sensor. Was the problem found? —Go to Step 12 Go to Step 6
932
1
89 E-41
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6E –162 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
6 Using the DVM and check the ECT sensor.
1. Ignition “Off ”, engine “Off ”.
2. Disconnect ECT sensor connector.
3. Measure the resistance of ECT sensor.
Does the tester indicate standard resistance as shown
in the following table?
Standard
resistance Go to Step 7Go to Step 12
7 Using the DVM and check the ECT sensor signal circuit.
1. Ignition “On ”, engine “Off ”.
2. Disconnect the ECT sensor connector.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
Approx imately 5.0V Go to Step 10 Less than 1V:
Go to Step 8
More than
specified value: Go to Step 9
8 Repair the open circuit between the ECM and ECT sensor.
Was the problem solved?
— Verify repair Go to Step 14
Step Action Value(s) Yes No
Temperature (
°C) Re sista nce (
) (Appro xima te ly )
-20 16100 0 5760
20 2370
40 1080
60 537
80 290
100 161
120 95
1
2
ECT Sensor
1
2
V
1 E-41
891
E-41
C-57(B)

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E –163
9 Repair the short to voltage circuit between the ECM
and ECT sensor.
Was the problem solved?
— Verify repair Go to Step 14
10 Using the DVM and check the ECT sensor ground circuit.
1. Ignition “On ”, engine “Off ”.
2. Disconnect the ECT sensor connector.
3. Check the circuit for short to power supply circuit.
Was the DVM indicated specified value?
Less than 1V Go to Step 11 Repair faulty
harness and verify repair
11 Using the DVM and check the ECT sensor ground circuit.
Breaker box is available:
1. Ignition “Off ”, engine “Off ”.
2. Install the breaker box as type A. (ECM disconnected) Ref. Page 6E-103
3. Disconnect the ECT sensor 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 ECT sensor connector ECM connector.
3. Check the circuit for open circuit.
Was the problem found?
— Repair faulty
harness and verify repair Go to Step 14
Step Action Value(s) Yes No
891
E-41
C-57(B)
2
V
E-41
E-4193Breaker Box



2
93
E-41
C-57

6E–164 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
12 Substitute a known good ECT sensor assembly and
recheck.
Was the problem solved?—Go to Step 13Go to Step 14
13 Replace the ECT sensor.
Is the action complete?—Verify repair—
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 15
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.—Verify repair— Step Action Value(s) Yes No

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E –165
Diagnostic Trouble Code (DTC) P0115 (Sy mptom Code 2) (Flash Code 14)
Engine Coolant Temperature Sensor Circuit Low 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 P0115 (Symptom Code 2) 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 P0115 (Symptom Code 2) 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 ECT 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 ECT sensor. Was the problem found? —Go to Step 8 Go to Step 6
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89 E-41
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6E –166 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
6 Using the DVM and check the ECT sensor.
1. Ignition “Off ”, engine “Off ”.
2. Disconnect ECT sensor connector.
3. Measure the resistance of ECT sensor.
Does the tester indicate standard resistance as shown
in the following table?
Standard
resistance Go to Step 7Go to Step 8
Step Action Value(s) Yes No
Temperature (
°C) Re sista nce (
) (Appro xima te ly )
-20 16100 0 5760
20 2370
40 1080
60 537
80 290
100 161
120 95
1
2
ECT Sensor
1
2

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E –167
7 Using the DVM and check the ECT sensor signal
circuit.
Breaker box is available:
1. Ignition “Off ”, engine “Off ”.
2. Install the breaker box as type A. (ECM disconnected) Ref. Page 6E-103
3. Disconnect the ECT sensor connector.
4. Check the circuit for short to sensor ground or ground circuit.
Was the problem found?
Breaker box is not available: 1. Ignition “Off ”, engine “Off ”.
2. Disconnect the ECT sensor connector and ECM connector.
3. Check the circuit for short to sensor ground or ground circuit.
Was the problem found?
— Repair faulty
harness and verify repair Go to Step 10
8 Substitute a known good ECT sensor assembly and recheck.
Was the problem solved? —Go to Step 9 Go to Step 10
9 Replace the ECT sensor. 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 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. —Verify repair —
Step Action Value(s) Yes No
8993


Breaker Box


93
89
C-57(B)

6E–168 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) P0180 (SYMPTOM CODE B)
(FLASH CODE 15) FUEL TEMPERATURE SENSOR CIRCUIT RANGE/
PERFORMANCE
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The fuel temperature sensor is assembled inside of the
pump control unit (PSG). The signal of fuel temperature
is sent via the CAN-bus from the PSG to ECM.
If the fuel temperature is ex cessively high or low
condition, DTC P0180 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 and PSG-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 “Fuel Temperature” display on the Tech2 while
Flash
CodeCode Symptom
CodeMIL DTC Name DTC Setting Condition Fail-Safe (Back Up)
15 P0180 B ON Fuel Temperature Sensor Cir-
cuit Range/PerformanceFT sensor output is high tem-
pe ra ture (mo re tha n
150deg.C) or low temperature
(below -40deg.C).The ECM use 75de g.C condi-
tions as substitute.