check engine ISUZU TF SERIES 2004 Workshop Manual

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

6E-198 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No

E-61(B)





 BANK2
E-78









E-61(B)







E-78




7
Using the DVM and check the O2 sensor circuit for the
affected bank.
1. Ignition "Off", engine "Off".
2. Disconnect the O2 sensor connector for the
affected bank.
3. Check the circuit for short to heater ground circuit.
Was the DVM indicated specified value?
O2 Sensor BANK1/BANK2









No continuity
Go to Step 9
Go to Step 8
8
Repair the short to heater ground circuit.
Was the problem found?
- Verify repair Go to Step 15

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-199
Step Action Value (s) Yes No
9
1. Using the Tech 2, ignition "On" and engine "On".
2. Monitor the "Mass Air Flow" in the data display.
Does the Tech 2 indicate correct "Mass Air Flow" as
shown in the following graph, when engine speed is
increasing little by little?
Characteris tic of MAF Sens or -Ref erence (No Engine Load)-
0 5 10 15 20 25 30 35 40 45 50
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Eng i ne Speed ( r pm) ( T ech2 R eadi ng )
Mass Air Flow (g/s)
( T ec h2 R eadi ng)
- Go to Step 11 Go to Step 10
10
Remove the MAF & IAT sensor assembly and check
for the following conditions.

Objects blocking the air cleaner.

Objects blocking the MAF 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 Refer to DTC
P0101 and 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 accrodance with procedure.
Was the engine speed changed, when the IAC Valve
is operating step by step?
- Go to Step 13 Go 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 Refer to DTC
P1508/P1509
and Go to Step
13
13
Check for injector for the affected bank.
Refer to 6E-106 "Injector Coil Test & Injector Balance
Test Procedure"
Was the injector operation correct?
- Go to Step 14 Refer to Injector
Coil Test &
Injecotr Balance
Test Procedure
14
Check for fuel pressure.
Refer to 6E-116 "Fuel System Diagnosis".
Was the fuel pressure correct?
- Go to Step 15 Refer to Fuel
System
Diagnosis
15
Replace the O2 sensor for the affected bank.
Was the problem solved?
- Verify repair Go to Step 16

6E-202 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)
P0132 A O2 Sensor Circuit High
Voltage (Bank 1
Sensor 1) 15
P0152 A O2 Sensor Circuit High
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
and 110
.
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 below
600mV 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 the HO2S voltage remains
excessively high for an extended period of time, DTC
P0132 or P0152 will be set.
DIAGNOSTIC AIDS
Check the following items:
 Fuel pressure – The system will go rich if pressure is
too high. The ECM can compensate for some
increase. However, if fuel pressure is too high, a DTC
P0132 or P0152 may be set. Refer to 6E-116 Fue
l
System Diagnosis.
 Perform “Injector Balance Test" – Refer to 6E-116
Fuel System Diagnosis.
 Check the canister for fuel saturation – If full of fuel,
check canister control and hoses.
 MAF sensor –The system can go rich if MAF senso
r
signal indicates an engine airflow measurement that
is not correct. Disconnect the MAF sensor to see it
the rich condition is corrected. If so, replace the MAF
sensor.

 Check for a leak in the fuel pressure regulato
r
diaphragm by checking the vacuum line to the
regulator for the presence of fuel. There should be no
fuel in the vacuum line.

An intermittent throttle position sensor output will
cause the system to go rich due to a false indication
of the engine accelerating.
 Shorted Heated Oxygen Sensor (HO2S) –If the
HO2S is internally shorted, the HO2S voltage
displayed on the Tech 2 will be over 1 volt. Try
disconnecting the affected HO2S with the key “ON,"
engine “OFF." If the displayed HO2S voltage
changes from over 1000 mV to around 450 mV,
replace the HO2S. Silicon contamination of the
HO2S can also cause a high HO2S voltage to be
indicated. This condition is indicated by a powdery
white deposit on the portion of the HO2S exposed to
the exhaust stream. If contamination is noticed,
replace the affected HO2S.
 Open HO2S Signal Circuit or Faulty HO2S–
A poor
connection or open in the HO2S signal circuit can
cause the DTC to set during deceleration fuel mode.
An HO2S which is faulty and not allowing a full
voltage swing between the rich and lean thresholds
can also cause this condition. Operate the vehicle by
monitoring the HO2S voltage with a Tech 2. If the
HO2S voltage is limited within a range between 300
mV to 600 mV, check the HO2S signal circuit wiring
and associated terminal conditions.
 If none of the above conditions are present, replace
the affected HO2S.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-203
Diagnostic Trouble Code (DTC) P0132 (Flash Code 15) O2 Sensor Circuit High
Voltage (Bank 1 Sensor 1)
Diagnostic Trouble Code (DTC) P0152 (Flash Code 15) O2 Sensor Circuit High
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 P0132 or P0152 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 P0132 or P0152 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-204 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.
1. Ignition "On", engine "Off".
2. Disconnect the O2 sensor connector for the
affected cylinder.
3. Check the circuit for short to power supply circuit.
Was the DVM indicated specifed value?
E-77/E-78 BANK1/BANK2
VV





Less than 1V
Go to Step 15
Repair faulty
harness and
verify repair

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-205
Step Action Value (s) Yes No
7
Using the DVM and check the O2 sensor circuit for the
affected bank.
1. Ignition "Off", engine "Off".
2. Disconnect the O2 sensor connector for the
affected bank.
3. Check the circuit for short to heater power supply
circuit.
Was the DVM indicated specified value?
O2 Sensor BANK1/BANK2










No continuity
Go to Step 9
Go to Step 8
8
Repair the short to heater power supply circuit.
Was the problem found?
- Verify repair Go to Step 15
9
1. Using the Tech 2, ignition "On" and engine "On".
2. Monitor the "Mass Air Flow" in the data display.
Does the Tech 2 indicate correct "Mass Air Flow" as
shown in the following graph, when engine speed is
increasing little by little?
Characteris tic of MAF Sens or -Ref erence (No Engine Load)-
0 5 10 15 20 25 30 35 40 45 50
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Eng i ne Speed ( r pm) ( T ech2 R eadi ng )
Mass Air Flow (g/s)
( T ec h2 R eadi ng)
- Go to Step 11 Go to Step 10
10
Remove the MAF & IAT sensor assembly and check
for the following conditions.

-Objects blocking the air cleaner.

Objects blocking the MAF 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 Refer to DTC
P0101 and Go to
Step 11