ISUZU TF SERIES 2004 Workshop Manual

ENGINE DRIVEABILITY AND EMISSIONS 6E–215
Diagnostic Aids
Check for the following conditions:
Heated oxygen sensor wiring - The sensor pigtail
may be routed incorrectly and contacting the ex haust
system.
Poor ECM to engine block ground.
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
diagnostic Trouble Code P1171 may be set. Refer to
Fuel System Diagnosis.
Lean injector(s) - Perform “Injector Balance Test.”Vacuum leaks - Check for disconnected or damaged
vacuum hoses and for vacuum leaks at the intake
manifold, throttle body, and PCV system.
Ex haust leaks - An ex haust leak may cause outside
air to be pulled into the ex haust gas stream past the
HO2S, causing the system to appear lean. Check for
exhaust leaks that may cause a false lean condition
to be indicated.
Fuel contamination - Water, even in small amounts,
can be delivered to the fuel injectors. The water can
cause a lean ex haust to be indicated, Ex cessive
alcohol in the fuel can also cause this condition.
Refer to Fuel System Diagnosis for the procedure to
check for fuel contamination.
Diagnostic Trouble Code (DTC) P1171
Fuel Supply Sy stem Lean During Power Enrichment
Step A ction Value(s) Yes No
1 Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go 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 P1171 stored as “Present Failure”?—Go to Step 3Refer 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 P1171 stored in this ignition cycle?—Go to Step 4Refer 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” in
accordance with accelerator pedal operation? —Go to Step 6Go to Step 5
5 Check for the following conditions.
Objects blocking the throttle valve.
Incorrectly installed.
If a problem is found, repair as necessary.
Was the problem found?—Verify repair Go to Step 12
6 1. Using the Tech 2, ignition “On” and engine “On”.
2. Monitor the “Manifold Absolute Pressure” in the
data display.
Does the Tech 2 indicate correct “Manifold Absolute
Pressure” in accordance with engine speed or
acceleration? —Go to Step 8Go to Step 7

6E–216 ENGINE DRIVEABILITY AND EMISSIONS
7 Remove the MAP sensor and check for the following
conditions.
Objects blocking the air cleaner.
Objects blocking the MAP 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 Go to Step 13
8 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 accordance with procedure.
Was the engine speed changed, when the IAC valve
is operating step by step?—Go to Step 10Go to Step 9
9 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 Go to Step 14
10 Check for injector for the affected bank.
Refer to “Injector Coil Test & Injector Balance Test
Procedure” 6E-98 page.
Was the injector operation correct?
—Go to Step 11Refer to Injector
Coil Test &
Injector
Balance Test
Procedure
11 Check for fuel pressure.
Refer to “Fuel System Diagnosis” 6E-108 page.
Was the fuel pressure correct? —Go to Step 15Refer to Fuel
System
Diagnosis
12 Replace the TPS.
Is the action complete?—Veri fy repai r—
13 Replace the MAP sensor.
Is the action complete?—Veri fy repai r—
14 Replace the IAC valve.
Is the action complete?—Veri fy repai r—
15 Replace the O
2 sensor.
Was the problem solved?—Verify repair Go to Step 16
16 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 17
17 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.—Veri fy repai r— Step A ction Value(s) Yes No

ENGINE DRIVEABILITY AND EMISSIONS 6E–217
DIAGNOSTIC TROUBLE CODE (DTC) P1625 ECM SYSTEM RESET
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The engine control module (ECM) monitors unex pected
ECM reset. This will not turn on MIL light on, only
records code DTC P1625.
Diagnostic Aids
Check for the follwing conditions:
P1625 alone stored does not need diagnosis. Clear
DTC code.
NOTE: DTC P1625 is a DTC to record a ECM reset
history. If DTC P1625 is not reset and no engine
abnormality occurs after learing the DTC, no farther
diagnostic procedures are required.
Diagnostic Trouble Code (DTC) P1625 ECM System Reset
Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P1625 B ECM Sy ste m Reset ECM re se t ha s o ccurre d o ther tha n “On”. Engine control disabled.
Step A ction Value(s) Yes No
1 Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go 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 P1625 stored as “Present Failure”?—Go to Step 3Refer 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 P1625 stored in this ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 Is the Immobilizer function programmed in the ECM?—Verify repair Go to Step 5
5 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 6
6 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.—Veri fy repai r—

6E–218 ENGINE DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) P1626 IMMOBILIZER NO SIGNAL
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The ECM decides whether that is an abnomality in the
immobilizer control system. DTC P1626 is recorded by
the ECM when no response from immobiliser.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM and Immobilizer-Inspect
harness connectors for backed out terminals,
improper mating, broken locks, improperly formed ordamaged terminals, and poor terminal to wire
connection.
Damaged harness Inspect the wiring harness for
damage, If the harness appears to be OK, disconnect
the ECM and Immobilizer, turn the ignition “ON” and
observe a voltmeter connected to the suspect driver
circuit at the ECM and Immobilizer harnass connector
while moving connectors and wiring harnesses
relates to the MIL. A change in voltage will indicate
the location of the fault.
Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P1626 - Immobilizer No Signal No response from immobilizer control unit. 1. Engine does not start.
2. Check engine lamp flash.

ENGINE DRIVEABILITY AND EMISSIONS 6E–219
Diagnostic Trouble Code (DTC) P1626 Immobilizer No Signal
Step A ction Value(s) Yes No
1 Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go 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 P1626 stored as “Present Failure”?—Go to Step 3Refer 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 P1626 stored in this ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Select “Immobilizer” in the system selection menu
“Body”.
3. Select “Read DTC Info Ordered By Priority” in the
“Diagnositic Trouble Code”.
Was the DTC B0007 stored in this ignition cycle?—Refer to
“Immobilizer
Workshop
Manual” & Go
to DTC Chart
B0007 Go to Step 5
5 Check for poor/faulty connection at the immobilizer
control unit connector or ECM connector. If a poor/
faulty connection is found, repair as necessary.
Was the problem found?
—Verify repair Go to Step 6
6 Using the DVM and check the “CHECK ENGINE”
lamp circuit.
1. Ignition “Off”, engine “Off”.
2. Disconnect the meter connector and immobilizer
control unit connector.
3. Ignition “On”.
4. Check the circuit for short to power supply circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 7
3223 78 C-56(J2) B-68
VV
B-24 B-68
17
7

6E–220 ENGINE DRIVEABILITY AND EMISSIONS
7 Using the DVM and check the “CHECK ENGINE”
lamp circuit.
Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type A. (ECM
disconnected) Refer to 6E-88 page.
3. Disconnect the immobilizer control unit connector.
4. Check the circuit for open or short to ground
circuit.
Was the problem found?
Breaker box is not available:
1. Ignition “Off”, engine “Off”.
2. Disconnect the the immobilizer control unit
connector and ECM connector.
3. Check the circuit for open or short to ground
circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 8
8 Using the DVM and check the VSS signal circuit.
1. Ignition “Off”, engine “Off”.
2. Disconnect the immobilizer control unit connector
and ECM connector.
3. Ignition “On”.
4. Check the circuit for short to power supply circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Step 9 Step A ction Value(s) Yes No
J2-32
Brea ker Bo xB-24





C-56(J2) 327B-68
VV
C-56(J2)
23
7
B-68

ENGINE DRIVEABILITY AND EMISSIONS 6E–221
9 Using the DVM and check the VSS signal circuit.
Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type A. (ECM
disconnected) Refer to 6E-88 page.
3. Disconnect the immobilizer control unit connector.
4 . C h e c k t h e c i r c u i t f o r o p e n o r s h o t t o g r o u n d c i r c u i t .
Was the problem found?
Breaker box is not available:
1. Ignition “Off”, engine “Off”.
2. Disconnect the immobilizer control unit connector
and ECM connector.
3. Check the circuit for open or short to ground
circuit.
Was the problem found?
—Repair faulty
harness and
verify repair Go to Srtep 10
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.—Veri fy repai r— Step A ction Value(s) Yes No
J2-23Breaker BoxB-68




23B-68
C-56(J2)
8

6E–222 ENGINE DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) P1631
IMMOBILIZER WRONG SIGNAL
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The ECM decides whether that is an abnomality in the
immobilizer control system. DTC P1631 is recorded by
the ECM when received response was not correct.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM and Immobilizer-Inspect
harness connectors for backed out terminals,
improper mating, broken locks, improperly formed ordamaged terminals, and poor terminal to wire
connection.
Damaged harness-Inspect the wiring harness for
damage, If the harness appears to be OK, disconnect
the ECM and Immobilizer, turn the ignition “ON” and
observe a voltmeter connected to the suspect driver
circuit at the ECM and Immobilizer harnass connector
while moving connectors and wiring harnesses
relates to the MIL. A change in voltage will indicate
the location of the fault.
Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P1631 - Immobilizer Wrong Signal Received response is not correct. 1. Engine does not start.
2. Check engine lamp flash.

ENGINE DRIVEABILITY AND EMISSIONS 6E–223
Diagnostic Trouble Code (DTC) P1631 Immobilizer Wrong Signal
Step A ction Value(s) Yes No
1 Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go 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 P1631 stored as “Present Failure”?—Go to Step 3Refer 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 P1631 stored in this ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Select “Immobilizer” in the system selection menu
“Body”.
3. Select “Read DTC Info Ordered By Priority” in the
“Diagnositic Trouble Code”.
Was the DTC B0007 stored in this ignition cycle?—Refer to
“Immobilizer
Workshop
Manual” & Go
to DTC Chart
B0007 Go to Step 5
5 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 6
6 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.—Veri fy repai r—

6E–224 ENGINE DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) P1648
WRONG SECURITY CODE ENTERED
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The ECM decides whether that is an abnomality in the
immobilizer control system. DTC P1648 is recorded by
the ECM when received incorrect security code.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM and Immobilizer-Inspect
harness connectors for backed out terminals,
improper mating, broken locks, improperly formed ordamaged terminals, and poor terminal to wire
connection.
Damaged harness Inspect the wiring harness for
damage, If the harness appears to be OK, disconnect
the ECM and Immobilizer, turn the ignition “ON” and
observe a voltmeter connected to the suspect driver
circuit at the ECM and Immobilizer harnass connector
while moving connectors and wiring harnesses
relates to the MIL. A change in voltage will indicate
the location of the fault.
Code Type DTC Name DTC Setting Condition Fail-Safe (Back Up)
P1648 - Wrong Security Code Entered Received incorrect security code. 1. Engine does not start.
2. Check engine lamp flash.