2004 ISUZU TF SERIES Workshop Manual

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Page 2201 of 4264

ISUZU TF SERIES 2004 Workshop Manual 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. Disc

Page 2202 of 4264

ISUZU TF SERIES 2004 Workshop Manual 6E-206 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
11
1. Using the Tech 2, ignition "On" and engine "On".
2. Select the "Miscellaneous Test" and perform the
"IAC Co

Page 2203 of 4264

ISUZU TF SERIES 2004 Workshop Manual 3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-207
DIAGNOSTIC TROUBLE CODE (DTC) P0134 (FLASH CODE 15) O2 SENSOR
CIRCUIT NO ACTIVITY DETECTED (BANK 1 SENSOR 1)
DIAGNOSTIC TROUBLE CODE (DTC) P0154 (FLASH

Page 2204 of 4264

ISUZU TF SERIES 2004 Workshop Manual 6E-208 3.5L ENGINE DRIVEABILITY AND EMISSIONS
CIRCUIT DESCRIPTION
The Engine Control Module (ECM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) high and low circu

6E-208 3.5L ENGINE DRIVEABILITY AND EMISSIONS
CIRCUIT DESCRIPTION
The Engine Control Module (ECM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) high and low circuits. The ECM
constantly monitors the HO2S signal during “closed
loop" operation and compensates for a rich or lean
condition by decreasing or increasing injector pulse
width as necessary. If the HO2S voltage remains a
t
or near the 450 mV bias for an extended period of
time, DTC P0134 or P0154 will be set, indicating an
open sensor signal or sensor low circuit.
DIAGNOSTIC AIDS
Check for the following conditions:
Poor connection or damaged harness – Inspect the
harness connectors for backed-out terminals,
improper mating, broken locks, improperly formed o
r
damaged terminals, poor terminal-to-wire connection,
and damaged harness.
Faulty HO2S heater or heater circuit –With the
ignition “ON," engine “OFF," after a cool down period,
the HO2S voltage displayed on the Tech 2 is
normally 455-460 mV. A reading over 1000 m
V
indicates a signal line shorted to voltage. A reading
under 5 mV indicates a signal line shorted to ground
or signal lines shorted together.
Intermittent test –With the Ignition “ON," monitor the
HO2S signal voltage while moving the wiring harness
and related connectors. If the fault is induced, the
HO2S signal voltage will change. This may help
isolate the location of the malfunction.

Diagnostic Trouble Code (DTC) P0134 (Flash Code 15) O2 Sensor Circuit No
Activity Detected (Bank 1 Sensor 1)
Diagnostic Trouble Code (DTC) P0154 (Flash Code 15) O2 Sensor Circuit No
Activity Detected (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 P0134 or P0154 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 P0134 or P0154 stored in this ignition
cycle?
- Go to Step 4 Refer to
Diagnostic Aids
and Go to Step 4

Page 2205 of 4264

ISUZU TF SERIES 2004 Workshop Manual 3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-209
Step Action Value (s) Yes No
4
Check for poor/faulty connection at the O2 sensor or
ECM connector. If a poor/faulty connection is found,
repair

Page 2206 of 4264

ISUZU TF SERIES 2004 Workshop Manual 6E-210 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Step Action Value (s) Yes No
7
Repair the open or short to ground circuit between the
fuel pump relay and O2 sensor heater for the affected
cyli

Page 2207 of 4264

ISUZU TF SERIES 2004 Workshop Manual 3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-211
DIAGNOSTIC TROUBLE CODE (DTC) P0171 (FLASH CODE 44) O2 SENSOR
SYSTEM TOO LEAN (BANK 1)
DIAGNOSTIC TROUBLE CODE (DTC) P0174 (FLASH CODE 44) O2 SENSOR
S

Page 2208 of 4264

ISUZU TF SERIES 2004 Workshop Manual 6E-212 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)
P0171 B

6E-212 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)
P0171 B O2 Sensor System Too
Lean (Bank 1) 44

P0174 B O2 Sensor System Too
Lean (Bank 2) 1. No DTC relating to MAF sensor, IAT sensor, ECT sensor,
TPS, CMP sensor, CKP sensor, VSS, injector control
circuit, ignition control circuit, O2 sensor circuit low voltage
& high voltage (bank 1 & 2) and O2 sensor circuit no
activity (bank 1 & 2).
2. Engine speed is more than 600rpm.
3. Intake air temperature is more than 50C.
4. Engine coolant temperature is between 35C and 120C.
5. Engine load is more than 20%.
6. EVAP purge solenoid valve on-duty is below 100%.
7. Air-fuel ratio correction volume is more than 150%
for 20 seconds. No fail-safe function.

CIRCUIT DESCRIPTION
To provide the best possible combination of driveability,
fuel economy, and emission control, a “closed loop"
air/fuel metering system is used. While in “closed loop,"
the Engine Control Module (ECM) monitors the HO2S
signals and adjusts fuel delivery based upon the HO2S
signal voltages. A change made to fuel delivery will be
indicated by the long and short term fuel trim values
which can be monitored with a Tech 2. Ideal fuel trim
values are around 0%; if the HO2S signals are
indicating a lean condition the ECM will add fuel,
resulting in fuel trim values above 0%. If a rich condition
is detected, the fuel trim values will be below 0%,
indicating that the ECM is reducing the amount of fuel
delivered. If an excessively lean condition is detected,
the ECM will set DTC P0171 or P0174.
The ECM's maximum authority to control long term fuel
trim allows a range between –15% (automatic
transmission) or –12% (manual transmission) and
+20%. The ECM monitors fuel trim under various
engine speed/load fuel trim cells before determining the
status the fuel trim diagnostic.

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 HO2S display on the Tech 2 while moving
connectors and wiring harnesses related to the
engine harness. A change in the display will indicate
the location of the fault.

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