ISUZU TF SERIES 2004 Workshop Manual

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-175
Step Action Value (s) Yes No
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?
ECT Sensor






Temperature (
C) Resistance ()
(Approximately)
-20 30300
0 9850
20 3650
40 1540
60 649
100 182
120 104

Standard
resistance
Go to Step 7
Go 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?
E-69
V



Approximately
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?
E-60(A)
E-69




- Verify repair Go to Step 14

6E-176 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
9
Repair the short to voltage circuit between the ECM
and ECT sensor.
Was the problem solved?
E-60(A)
E-69




- 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?
E-69
V




Less than 1V
Go to Step 11
Repair faulty
harness and
verify repair

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-177
Step Action Value (s) Yes No
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)
Refer to 6E-95 page.
3. Disconnect the ECT sensor connector.
4. Check the circuit for open circuit.
Was the problem found?
A22
Breaker Box
E-69






Breaker box is not available:
1. Ignition "Off", engine "Off".
2. Disconnect the ECT sensor connector.
3. Check the circuit for open circuit.
Was the problem found?
E-60(A)
E-69










-

Repair faulty
harness and
verify repair

Go to Step 14
12
Substitute a known good ECT sensor assembly and
recheck.
Was the problem solved?
- Go to Step 13 Go 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

6E-178 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
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 -

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-179
DIAGNOSTIC TROUBLE CODE (DTC) P0121 (FLASH CODE 21) THROTTLE
POSITION SENSOR (TPS) CIRCUIT RANGE/PERFORMANCE



RUW46EMF000101

Condition For Setting The DTC and Action Taken When The DTC Sets
Flash
Code Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
21
P0121
A
Throttle Position
Sensor
Range/Performance
1. No DTC relating to barometer sensor, ECT sensor, CMP
sensor, CKP sensor, MAF sensor and TPS (low input &
high input).
2. Engine speed is more than 2000rpm.
3. Engine coolant temperature is more than 75
C.
4. TPS output voltage is between 0.24V and 0.26V.
Above conditions are met for 3 seconds.
OR
1. No DTC relating to barometer sensor, ECT sensor, CMP
sensor, CKP sensor, MAF sensor and TPS (low input &
high input).
2. Engine speed is below 3200rpm.
3. Engine coolant temperature is more than 75
C.
4. TPS output voltage is between 4.54V and 4.56V.
Above conditions are met for 3 seconds. No fail-safe function.

6E-180 3.5L ENGINE DRIVEABILITY AND EMISSIONS
CIRCUIT DESCRIPTION
The TPS circuit provides a voltage signal that changes
relative to throttle blade angle. The signal voltage will
vary from about 0.6 volts at closed throttle to about 4.5
volts at wide open throttle (WOT).
The TPS signal is one of the most important inputs
used by the Engine Control Module (ECM) for fuel
control and many of the ECM-controlled outputs. The
ECM monitors throttle position and compares actual
throttle position from the TPS to a predicted TPS value
calculated from engine speed. If the ECM detects an
out-of-range condition, DTC P0121 will set.

DIAGNOSTIC AIDS
Check for the following conditions:
 Poor connection at ECM – Inspect harness
connectors for backed-out terminals, imprope
r
mating, broken locks improperly formed or damaged
terminals, and poor terminal-to-wire connection.
 Damaged harness –Inspect the wiring harness fo
r
damage. If the harness appears to be OK, observe
the ECT display on the Tech 2 while moving
connectors and wiring harnesses related to the
sensor. A change in the display will indicate the
location of the fault.
If DTC P0121 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

Diagnostic Trouble Code (DTC) P0121 (Flash Code 21) Throttle Position
Sensor (TPS) Circuit Range/Performance
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. 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 P0121 stored as "Present Failure"?
- Go to Step 3 Refer 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 P0121 stored in this ignition cycle?
- Go to Step 4 Refer to
Diagnostic Aids
and Go to Step 4
4

1. Using the Tech 2, ignition "On" and engine "Off".
2. Monitor the "Throttle Position" in the data display.
Does the Tech 2 indicate correct "Throttle Position"
from 0% to 100% depending on accelerator pedal
operation?
- Go to Step 6 Go to Step 5
5
1. Using the Tech 2, ignition "On" and engine "Off
2. Monitor the "Throttle Position" in the data display.
3. Adjust the TPS within 0% to 100%.
Was the problem solved?
- Verify repair Go to Step 12

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-181
Step Action Value (s) Yes No
6
Check for the following conditions.

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 7
7
Check for poor/faulty connection at the TPS or ECM
connector. If a poor/faulty connection is found, repair
the faulty terminal.
Was the problem found?
E-61(B)




E-68




- Verify repair Go to Step 8
8
Visually check the TPS.
Was the problem found?
- Go to Step 12 Go to Step 9
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?
E-68


V


Less than 1V
Go to Step 10
Repair faulty
harness and
verify repair
10
Check any accessory parts which may cause electric
interference.
Was the problem found?
- Remove the
accessory parts
and verify repair Go to Step 11
11
Check the shield wire for open or short circuit.
Was the problem found?
- Verify repair Go to Step 12
12
Substitute a known good TPS and recheck.
Was the problem solved?
- Go to Step 13 Go to Step 14
13
Replace the TPS.
Is the action complete?
- Verify repair -

6E-182 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
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 -

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-183
DIAGNOSTIC TROUBLE CODE (DTC) P0122 (FLASH CODE 21) THROTTLE
POSITION SENSOR CIRCUIT LOW INPUT



RUW46EMF000101

Condition For Setting The DTC and Action Taken When The DTC Sets
Flash
Code Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
21 P0122 A Throttle Position
Sensor Low Input TPS output voltage is below 0.24V. The ECM uses default throttle
position value based on mass air
flow and engine speed.

CIRCUIT DESCRIPTION
The TPS circuit provides a voltage signal that changes
relative to throttle blade angle. The signal voltage will
vary from below 0.6 volts at closed throttle to about 4.5
volts at wide open throttle (WOT).
The TPS signal is used by the Engine Control Module
(ECM) for fuel control and many of the ECM-controlled
outputs.

DIAGNOSTIC AIDS
Check for the following conditions:
 Poor connection at ECM – Inspect harness
connectors for backed-out terminals, imprope
r
mating, broken locks, improperly formed or damaged
terminals, and poor terminal-to-wire connection.
 Damaged harness –Inspect the wiring harness fo
r
damage. If the harness appears to be OK, observe
the throttle position display on the Tech 2 while
moving connectors and wiring harnesses related to
the TPS. A change in the display will indicate the
location of the fault.
If DTC P0122 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

6E-184 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0122 (Flash Code 21) Throttle Position
Sensor Circuit Low Input
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. 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 P0122 stored as "Present Failure"?
- Go to Step 3 Refer 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 P0122 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 TPS or ECM
connector. If a poor/faulty connection is found, repair
as necessary.
Was the problem found?
E-61(B)




E-68




- Verify repair Go to Step 5
5
Visually check the TPS.
Was the problem found?
- Go to Step 10 Go to Step 6