ignition ISUZU TF SERIES 2004 Workshop Manual

6E-186 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
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-95 page.
3. Disconnect TPS connector.
4. Check the circuit for open, short to sensor ground
or short to ground circuit.
Was the problem found?
B26B39


Breaker BoxE-68







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?
E-61(B)
E-68












-

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 11 Go to Step 12
11
Replace the TPS.
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

6E-188 3.5L ENGINE DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) P0123 (FLASH CODE 21) THROTTLE
POSITION SENSOR CIRCUIT HIGH 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 P0123 A Throttle Position
Sensor High Input TPS output voltage is more than 4.56V. 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 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.
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 TPS 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.
 Faulty TPS –With the ignition key “ON," engine
“OFF," observe the TPS display on the Tech 2 while
slowly depressing the accelerator to wide open
throttle. If a voltage over 4.56 volts is seen at any
point in normal accelerator travel, replace the TPS.
If DTC P0123 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-189
Diagnostic Trouble Code (DTC) P0123 (Flash Code 21) Throttle Position
Sensor Circuit High 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 P0123 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 P0123 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 12 Go to Step 6

6E-190 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
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?
TPS










Measurement Terminal Resistance ()
1 - 2 Approximately 4.7k at idle position
Approximately 1.0k at WOT
2 – 3 Approximately 0.6k at idle position
Approximately 4.3k at WOT
1 – 3 Approximately 5.0k at idle position & WOT
Standard
resistance
Go to Step 7
Go to Step 12
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?
E-68


V


Approximately
5.0V
Go to Step 9
Go to Step 8
8
Repair the short to voltage circuit between the ECM
and TPS.
Was the problem solved?
E-68


E-61(B)

- Verify repair Go to Step 14

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-191
Step Action Value (s) Yes No
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
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?
E-68
V




Less than 1V
Go to Step 11
Repair faulty
harness and
verify repair
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-95 page.
3. Disconnect the TPS connector.
4. Check the circuit for open circuit.
Was the problem found?
E-68

B39
Breaker Box

6E-192 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
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?
E-61(B)
E-68







- 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 13 Go to Step 14
13
Replace the TPS.
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 -

6E-194 3.5L ENGINE DRIVEABILITY AND EMISSIONS
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)
P0131 A O2 Sensor Circuit Low
Voltage (Bank 1
Sensor 1) 15
P0151 A O2 Sensor Circuit Low
Voltage (Bank 2
Sensor 1) 1. No DTC relating to ECT sensor, CMP sensor, CKP sensor,
VSS, injector control circuit, ignition control circuit and O2
sensor circuit no activity (bank 1 & 2).
2. Engine speed is between 1000rpm and 4000rpm.
3. Engine coolant temperature is between 70
C and 110
C.
4. Vehicle speed is between 0km/h and 120km/h.
5. Engine load is between 80% and 160%.
6. Throttle position fluctuation is below 0.28V.
7. O2 sensor bank 1 or bank 2 output voltage is more than
400mV for 50 seconds. "Open Loop" fuel control.

CIRCUIT DESCRIPTION
The Engine Control Module (ECM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) signal high and signal low circuits. The
ECM constantly monitors the HO2S signal during
“closed loop" operation and compensates for a rich o
r
lean condition by decreasing or increasing injector pulse
width as necessary. If HO2S voltage remains
excessively low for an extended period of time, DTC
P0131 or P0151 will be set.
DIAGNOSTIC AIDS
Check for the following conditions:
 Heated oxygen sensor wiring – The sensor pigtail
may be routed incorrectly and contacting the exhaus
t
system.
 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 DTC
P0131 or P0151 may be set. Refer to 6E-116 Fue
l
System Diagnosis.

 Lean injector(s) – Perform “Injector Balance Test."
 Exhaust leaks – An exhaust leak may cause outside
air to be pulled into the exhaust gas stream past the
HO2S, causing the system to appear lean. Check fo
r
exhaust leaks that may cause a false lean condition
to be indicated.
 MAF sensor –The system can go lean if the MAF
sensor signal indicates an engine airflo
w
measurement that is not correct. Disconnect the MAF
sensor to see if the lean condition is corrected. If so,
replace the MAF sensor.
 Fuel contamination –Water, even in small amounts,
can be delivered to the fuel injectors. The water can
cause a lean exhaust to be indicated. Excessive
alcohol in the fuel can also cause this condition.
Refer to 6E-116 Fuel System Diagnosisfor the
procedure to check for fuel contamination.
 If none of the above conditions are present, replace
the affected HO2S.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-195
Diagnostic Trouble Code (DTC) P0131 (Flash Code 15) O2 Sensor Circuit Low
Voltage (Bank 1 Sensor 1)
Diagnostic Trouble Code (DTC) P0151 (Flash Code 15) O
2 Sensor Circuit Low
Voltage (Bank 2 Sensor 1)
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 P0131 or P0151 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 P0131 or P0151 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 O2 sensor or
ECM connector. If a poor/faulty connection is found,
repair as necessary.
Was the problem found?
E-77/E-78



E-61(B)




- Verify repair Go to Step 5

6E-196 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
5
Using the DVM and check the O2 sensor circuit for the
affected bank.
1. Ignition "On", engine "Off".
2. Disconnect the O2 sensor connector for the
affected bank.
3. Check the circuit for open, short to heater ground or
ground circuit.
Was the DVM indicated specified value?
E-77/E-78 BANK1/BANK2
V




Approximatly
450mV
Go to Step 7
Go to Step 6
6
Using the DVM and check the O2 sensor circuit for the
affected bank.
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 O2 sensor for the affected bank.
4. Check the circuit for open, short to heater ground or
short to ground circuit.
Was the problem found?
B21B22


Breaker BoxE-77










 BANK1


B21B22 Breaker Box
E-77








3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-197
Step Action Value (s) Yes No

B23B24


Breaker BoxE-78










 BANK2


B23B24 Breaker Box
E-78







Breaker box is not available:
1. Ignition "Off", engine "Off".
2. Disconnect the O2 sensor connector for the
affected bank and ECM connector.
3. Check the circuit for open, short to heater ground or
short to ground circuit.
Was the problem found?
E-61(B)






BANK1
E-77









E-61(B)








E-77


- Repair faulty
harness and
verify repair Go to Step 15