power ISUZU TF SERIES 2004 Workshop Manual

6E–270 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
6 Using the DVM and check the A/C compressor relay
power supply circuit.
1. Ignition “On”, engine “Off”.
2. Remove the A/C compressor relay from the relay
box .
3. Check the circuit for open or short to ground
circuit.
Was the DVM indicated specified value?
10-14.5V Go to Step 8Go to Step 7
7 Repair the open or short to ground circuit between the
ECM main relay and A/C compressor relay.
Is the action complete?—Verify repair— Step Action Value(s) Yes No
3
V
X-14

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–275
3 1. Using the Tech 2, ignition “On” and engine “Off”.
2. Select “F1: Clear DTC Information” in “F0:
Diagnostic Trouble Codes” with the Tech 2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F0: Read
DTC Infor As Stored By ECU” in the “F0:
Diagnostic Trouble Codes”.
Was the DTC P0703 (Symptom Code A) stored in this
ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 Check the “Stop Lamp fuse (15A)”.
If the fuse is burnt out, repair as necessary.
Was the problem found?—Verify repair Go to Step 5
5 Check for poor/faulty connection at the brake switch
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 brake switch 1.
1. Ignition “Off”, engine “Off”.
2. Remove the brake switch connector at the brake
pedal.
3. Check the brake switch 1.
Was the DVM indicated specified value?
Pedal is not
stepped on:
Continuity
Pedal stepped
on: No
continuity Go to Step 7Replace pedal
switch and
verify repair
7 Using the DVM and check the brake switch 1 power
supply circuit.
1. Ignition “Off”, engine “Off”.
2. Remove the brake switch connector from the
brake switch.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
10-14.5V Go to Step 9Go to Step 8 Step Action Value(s) Yes No
301
2 C-56 C-44




Brake Switch
V
1C-44

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–279
6 Using the DVM and check the brake switch 2 power
supply circuit.
1. Ignition “On”, engine “Off”.
2. Remove the brake switch connector from the
brake switch.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
10-14.5V Go to Step 8Go to Step 7
7 Repair the open circuit between the “ECM fuse (10A)”
and brake switch 2.
Is the action complete?—Verify repair—
8 Using the DVM and check the brake switch 2 circuit.
Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type B. (ECM
connected)
3. Ignition “On”, engine “Off”.
4. Check the circuit for open or short to voltage
circuit.
Was the DVM indicated specified value?
Breaker box is not available:
1. Ignition “On”, engine “Off”.
2. Back probe the DVM to the brake switch 2 and
check the circuit for open or short to voltage
circuit.
Was the problem found?
Pedal is not
stepped on:
10-14.5V
Pedal stepped
on: Less than
1V Go to Step 11Fix ed at 10-
14.5V: Go to
Step 9
Fix ed at less
than 1V: Go to
Step 10 Step Action Value(s) Yes No
V
3C-44
65Breaker Box
V
V
4 C-44

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–283
6 Using the DVM and check the clutch switch power supply circuit.
1. Ignition “On”, engine “Off”.
2. Remove the clutch switch connector from the clutch switch.
3. Check the circuit for open circuit.
Was the DVM indicated specified value?
10-14.5V Go to Step 8Go to Step 7
7 Repair the open circuit between the “ECM fuse (10A)” and clutch switch.
Is the action complete? — Verify repair —
8 Using the DVM and check the clutch switch circuit. Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type B. (ECM connected) Ref. Page 6E-104
3. Ignition “On”, engine “Off”.
4. Check the circuit for open or short to voltage circuit.
Was the DVM indicated specified value?
Breaker box is not available: 1. Ignition “On”, engine “Off”.
2. Back probe the DVM to the clutch switch and check the circuit for open or short to voltage
circuit.
Was the problem found?
Pedal is not
stepped on: 10-14.5V
Pedal stepped on: Less than 1V Go to Step 11 Fix ed at 10-
14.5V: Go to Step 9
Fix ed at less
than 1V: Go to Step 10
Step Action Value(s) Yes No
V
1
2
C-77
31Breaker Box
V
V
2
C-77

6E–288 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The TPS is a potentiometer connected to throttle shaft
on the throttle body. It is installed to the main TPS and
idle switch.
The engine control module (ECM) monitors the voltage
on the signal line and calculates throttle position. As the
throttle valve angle is changed when accelerator pedal
moved. The TPS signal also changed at a moved
throttle valve. As the throttle valve opens, the output
increases so that the output voltage should be high.
The ECM monitors the TPS supply voltage and TPS
output voltage. The supply voltage is out of range, DTC
P1120 (Symptom Code 7) or P1120 (Symptom Code 9)
will be stored. The output voltage excessively high, DTC
P1120 (Symptom Code 1) will be stored.
If the brake pedal is depressed during accelerator pedal
is depressing, DTC P1120 (Symptom Code D) will be
stored.
If the relation of idle switch and TPS position are
incorrect, DTC P1120 (Symptom Code E) will be stored.
Diagnostic Aids
An intermittent may be caused by the following:
Poor connections.
Misrouted harness.
Rubbed through wire insulation.
Broken wire inside the insulation.
Check for the following conditions:
Poor connection at ECM-Inspect harness connectors
for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal to wire connection.
Damaged harness-Inspect the wiring harness for
damage. If the harness appears to be OK, observe
the “Throttle Position”, “Idle Switch”, “Brake Switch 1”
and “Brake Switch 2” display on the Tech2 while
moving connectors and wiring harness related to the
sensor.
Diagnostic Trouble Code (DTC) P1120 (Sy mptom Code 1) (Flash Code 21)
Pedal/Throttle Position Sensor Circuit High Input
Flash
CodeCode Symptom
CodeMIL DTC Name DTC Setting Condition Fail-Safe (Back Up)
21 P1120 1 ON Pedal/Throttle Position Sen-
sor Circuit High InputThrottle position sensor out-
put voltage is more than 4.5V.ECM increa ses idle spe ed up
to 1400rpm.
7 ON Pedal/Throttle Position Sen-
sor Voltage Supply Circuit
High InputThrottle position sensor
power supply voltage is more
than 5.2V.
9 ON Pedal/Throttle Position Sen-
sor Voltage Supply Circuit
Lo w InputThrottle position sensor
power supply voltage is below
4.6V.
D ON Pedal/Throttle Position Sen-
sor Brake Switch Error1. Engine speed is more than
1700rpm.
2. Vehicle speed is more than
1.5km/h.
3. When brake pedal is
depressed during accelera-
tor pe da l is de pre ssing.
E ON Pedal/Throttle Position Sen-
sor Idle Position Switch Error1. Whe n idle switch is turne d
o ff, thro ttle positio n se nsor
wa s be lo w 0.35%.
or
2. Whe n idle switch is tune d
on, throttle position sensor
was more than 7.8%.
Step Action Value(s) Yes No
1Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go to On Board
Diagnostic
(OBD) System
Check

6E–290 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
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?
Standard
resistance Go to Step 7Go 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?
Approx imately
5.0V Go to Step 9Go to Step 8
8 Repair the short to voltage circuit between the ECM
and TPS.
Was the problem solved?
—Verify repair Go to Step 14 Step Action Value(s) Yes No
Measurement
Te r m i n a lRe sista nce (
)
1 - 2Approximately 0.4k
a t idle po sitio n
Approximately 4.0k
at WOT
2 - 3Approximately 4.3k
a t idle po sitio n
Approximately 0.8k
at WOT
1 - 3Approximately 4.6k
a t idle po sitio n &
WO T
TPS
123
1
23
V3 E-22
57
3 C-56
E-22

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–291
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?
Less than 1V Go to Step 10Repair 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?
Less than 1V Go to Step 11Repair faulty
harness and
verify repair Step Action Value(s) Yes No
V
2 E-22
V1E-22

6E–294 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
6 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 ground circuit.
Was the DVM indicated specified value?
Approx imately
5.0V Go to Step 12Go to Step 7
7 Repair the short to battery voltage circuit between the
ECM and TPS.
Was the problem solved?
—Verify repair Go to Step 8
8 Substitute a known good TPS and recheck.
Was the problem solved?—Go to Step 9Go to Step 10
9 Replace the TPS.
Is the action complete?—Verify repair—
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.—Verify repair— Step Action Value(s) Yes No
V3 E-22
57
3 C-56
E-22

6E–296 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
6 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 battery voltage
circuit.
Was the DVM indicated specified value?
Approx imately
5.0V Go to Step 10Go to Step 7
7 Using the DVM and check the TPS power supply
circuit.
1. Ignition “Off”, engine “Off”.
2. Disconnect the TPS connector and ECM
connector.
3. Check the circuit for short to TPS ground circuit.
Was the DVM indicated specified value?
No continuity Go to Step 9Go to Step 8
8 Repair the circuit for short to TPS ground circuit.
Is the action complete?—Verify repair—
9 Repair the short to ground circuit between the ECM
and TPS.
Was the problem solved?
—Verify repair Go to Step 12
10 Substitute a known good TPS and recheck.
Was the problem solved?—Go to Step 11Go to Step 12
11 Replace the TPS.
Is the action complete?—Verify repair— Step Action Value(s) Yes No
V3 E-22
3 1
E-22
57
3 C-56
E-22

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–309
7 Using the DVM and check the CKP sensor output
circuit.
Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type A. (ECM
disconnected) Ref. Page 6E-103
3. Disconnect the PSG (pump 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 ECM connector.
3. Disconnect the PSG (pump control unit)
connector.
4. 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 CKP sensor output
circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the PSG (pump control unit)
connector.
3. Check the circuit for short to power supply circuit.
Was the DVM indicated specified value?
Less than 1V Go to Step 9Repair faulty
harness and
verify repair Step Action Value(s) Yes No
E-691Breaker Box




918 C-57(B) E-6
8
V
E-6