2004 ISUZU TF SERIES brake

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–91
18 Brake Switch 2 Active/
InactiveInactive Inactive Inactive This displays operating status of the brake switch. This
should display "Active" when the brake pedal is stepped
on.
19 Clutch Switch (M/T
On ly )Active/
InactiveInactive Inactive Inactive This displays operating status of the clutch switch. This
should display "Active" when the clutch pedal is stepped
on.
20 Neutra l Switch On/Off On On On This displa ys o pe rating status of the neutra l switch. This
should display "On" when the gear position is neutral (M/T)
or P, N positio n (A/T).
21 A/C Informa tion
SwitchActive 12V/
Inactive 0VInactive 0V Inactive 0V Inactive 0V This displays the air conditioner request signal. This
should display "Active 12V" when the air conditioner switch
is switched on.
22 Dia gnostic Re quest Activ e 0V/
Inactive 12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis displays the diagnostic request signal. This should
display "Inactive 12V" when the Tech 2 is connected.
23 System Voltage V 10 - 15 10 - 15 10 - 15 This displays the system voltage measured by the ECM at
ignition feed.
24 Ma in Re la y Activ e /
InactiveActive Active Active This displays operating status for the ECM main relay. This
should display "Active" when the key switch is turned on
and while engine is running.
25 Glow Time Relay Activ e 0V/
Inactive12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis displays operating status for the glow relay. This
should display "Inactive 12V" when the engine is warm
uppe d.
26 Check Engine Light On/Off Off Off Off This displays operating status for the Check Engine Lamp.
This should display "On" when the Check Engine Lamp is
turned on.
27 Glow Time Telltale On/Off Off Off Off This displays operating status for the glow indicator lamp.
This sho uld display "On" whe n the glo w la mp is turne d o n.
28 Desired Engine Idle
Speedrpm 700 700 700 The desired engine idle speed that the ECM commanding.
The ECM compensates for various engine loads based on
engine coolant temperature.
29 A/C Re que st Activ e 0V/
Inactive 12VIna ctiv e
12VInactive
12VIna ctiv e
12VThis displays operating status of the A/C compressor. This
should display "Active 0V" when the compressor relay is
operated.
30 Immo bilize r Activ e /
InactiveInactive Inactive Inactive This should display "Inactive" when the immobilizer is
correctly operated.
31 Immo bilize r Signal Rece iv ed/
Not
Rece iv edNo t
Receive dNot
Re ceive dNot
Re ce iv e dThis sho uld displa y "No t Receive d" whe n the immo bilize r is
not activated.
32 Immo bilize r Function
ProgrammedYes/ No Yes Yes Yes This should display "Yes" when the immobilizer is correctly
programmed.
33 EGR Pulse Ratio
(Ex ha ust Ga s
Recirculatio n)% 85 - 90 85 - 90 85 - 90 This displays the duty signal from the ECM to control the
EGR flow amount. Tech 2 Parameter Units Idle 1500rpm 2000rpm Definition

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–123
46 P0645 4 ON A/C Compressor Relay
Circuit Voltage LowA/C compressor relay circuit
open or short to ground
circuit.No fail-safe function. A/C compressor relay circuit
is correct condition.1. A/C compressor relay
circuit open or short to
g r o u n d c i r c u i t .
2. Poor connector
c o n n e c t i o n .
3. A/C compressor relay
m a l f u n c t i o n .
4. ECM malfunction.41 —
8 ON A/C Compressor Relay
Circuit Voltage High A/C compressor relay circuit
short to voltage circuit.ECM malfunction.
——
25 P0703 A ON Brake Switch Circuit
Malfunction1. Throttle position is more
t h a n 0 % .
2. Engine speed is more
than 693rpm (4JA1-TC)
or 665rpm (4JH1-TC).
3. Vehicle speed is more
t h a n 0 k m / h .
4. Brake switch 1 signal and
brake switch 2 signal are
differently inputted to the
ECM since the ignition
switch was turned on.No fail-safe function. Brake switch 1 signal and
brake switch 2 signal are
correctly inputted to the
ECM.1. Brake switch 1 circuit
open, short to ground or
short to voltage circuit.
2. Poor connector
c o n n e c t i o n .
3. Brake switch 1
m a l f u n c t i o n .
4. ECM malfunction.30 —
B ON Brake Switch Circuit
Malfunction1. Throttle position is more
t h a n 0 % .
2. Engine speed is more
than 693rpm (4JA1-TC)
or 665rpm (4JH1-TC).
3. Vehicle speed is more
t h a n 0 k m / h .
4. Brake switch 1 signal and
brake switch 2 signal are
differently inputted to the
ECM.1. Brake switch 2 circuit
open or short to ground
c i r c u i t .
2. Poor connector
c o n n e c t i o n .
3. Brake switch 2
m a l f u n c t i o n .
4. ECM malfunction.65 —
57 P0704 6 ON Clutch Switch Input Circuit
MalfunctionClutch signal does not
change between vehicle
speed 1.5km/h and 80km/h
since ignition switch was
tuned on. No fail-safe function. Clutch signal correctly
changes.1. Clutch switch circuit
open, short to ground or
short to voltage circuit.
2. Poor connector
c o n n e c t i o n .
3. Clutch switch
m a l f u n c t i o n .
4. ECM malfunction.31 — —
86 P1105 1 ON Barometric Pressure Sensor
Circuit High InputBarometric pressure sensor
output voltage is more than
4.4V.ECM uses 1013hpa
condition as substitute.Barometric pressure sensor
output voltage is below 4.4V.ECM malfunction.
——
2 ON Barometric Pressure Sensor
Circuit Low InputBarometric pressure sensor
output voltage is below 1.5V.Barometric pressure sensor
output voltage is more than
1.5V.ECM malfunction.
—— Flash
CodeCodeSymptom
CodeMILDTC Name DTC Setting Condition Fail-Safe (Back Up) Recovery Condition Related Failure PartsRelated
ECM Pin
No.Related
Multiple
DTC4JA1-TC
(MT)4JH1-TC
(MT)4JH1-TC
(AT)

6E–124 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
21 P1120 1 ON Pedal/Throttle Position
Sensor Circuit High InputThrottle position sensor
output voltage is more than
4.5V.ECM increases idle speed up
to 1400rpm.Throttle position sensor
output voltage is below 4.5V.1. Sensor power supply
circuit short to voltage
c i r c u i t .
2. Sensor signal circuit
short to voltage circuit.
3. Sensor ground circuit
open or short to voltage
c i r c u i t .
4. Poor connector
c o n n e c t i o n .
5 . T P S m a l f u n c t i o n .
6. ECM malfunction.3 8 /
4 9 /
57—
7 ON Pedal/Throttle Position
Sensor Voltage Supply
Circuit High InputThrottle position sensor
power supply voltage is more
than 5.2V.Throttle position sensor
power supply voltage is
below 5.2V.1. Sensor power supply
circuit short to battery
voltage circuit.
2 . T P S m a l f u n c t i o n .
3. ECM malfunction.57 —
9 ON Pedal/Throttle Position
Sensor Voltage Supply
Circuit Low InputThrottle position sensor
power supply voltage is
below 4.6V.Throttle position sensor
power supply voltage is more
than 4.6V.1. Sensor power supply
circuit short to ground
c i r c u i t .
2 . T P S m a l f u n c t i o n .
3. ECM malfunction.57 —
D ON Pedal/Throttle Position
Sensor Brake Switch Error1. Engine speed is more
t h a n 1 7 0 0 r p m .
2. Vehicle speed is more
t h a n 1 . 5 k m / h .
3. When brake pedal is
depressed during
accelerator pedal is
d e p r e s s i n g . Throttle position is more than
20% or brake pedal is
released (switch is inactive). 1 . T h r o t t l e s t i c k i n g .
2. TPS incorrect adjusting.
3 . T P S m a l f u n c t i o n .
4. Brake switch
m a l f u n c t i o n .
5. ECM malfunction.3 0 /
3 8 /
65—
E ON Pedal/Throttle Position
Sensor Idle Position Switch
Error1. When idle switch is
turned off, throttle
position sensor was
b e l o w 0 . 3 5 % .
o r
2. When idle switch is tuned
on, throttle position
sensor was more than
7.8%.1. When throttle position
sensor is 100%, idle
s w i t c h t u r n s o f f .
2. When throttle position
sensor is 0%, idle switch
turns on.1 . T P S m a l f u n c t i o n .
2. Idle switch malfunction.
3. ECM malfunction.
3 8 /
69—
22 P1173 3 OFF Fuel Reduction Caused By
High Coolant TemperatureExcessive high engine
coolant temperature is
detected.No fail-safe function. Engine coolant temperature
is normal range.1 . E n g i n e o v e r h e a t .
2. ECT sensor malfunction.








3. ECM malfunction.89 —
7 OFF Fuel Reduction Caused By
High Fuel TemperatureFuel temperature is more
than 100 deg. C.PSG (pump control unit)
controls fuel injection
quantity based on engine
speed and fuel temperature.Fuel temperature is below
100 deg. C.1 . E C M m a l f u n c t i o n .
2. PSG (pump control unit)
malfunction.——
A OFF Fuel Reduction Caused By
Low Fuel TemperatureExcessive low fuel
temperature is detected.No fail-safe function. Fuel temperature is normal
range.1 . E C M m a l f u n c t i o n .
2. PSG (pump control unit)
malfunction.——— Flash
CodeCodeSymptom
CodeMILDTC Name DTC Setting Condition Fail-Safe (Back Up) Recovery Condition Related Failure PartsRelated
ECM Pin
No.Related
Multiple
DTC4JA1-TC
(MT)4JH1-TC
(MT)4JH1-TC
(AT)

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–273
DIAGNOSTIC TROUBLE CODE (DTC) P0703 (SYMPTOM CODE A)
(FLASH CODE 25) BRAKE SWITCH CIRCUIT MALFUNCTION
DIAGNOSTIC TROUBLE CODE (DTC) P0703 (SYMPTOM CODE B)
(FLASH CODE 25) BRAKE SWITCH CIRCUIT MALFUNCTION

6E–274 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The ECM monitors the brake switch signal on the feed
terminal to the ECM. If brake switch 1 or 2 circuit with
malfunction, DTC P0703 (Symptom Code A) or P0703
(Symptom Code B) 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 “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) P0703 (Symptom Code A) (Flash Code 25)
Brake Switch Circuit Malfunction
Flash
CodeCode Symptom
CodeMIL DTC Name DTC Setting Condition Fail-Safe (Back Up)
25 P0703 A ON Bra ke Switch Circuit
Malfunctio n1. Thro ttle po sitio n is more
tha n 0%.
2. Engine speed is more than
693rpm (4JA1-TC) or
665rpm (4JH1-TC).
3. Vehicle speed is more than
0km/h.
4. Brake switch 1 signal and
brake switch 2 signal are
differently inputted to the
ECM since the ignition
sw it ch w a s tur ne d o n.No fa il-sa fe fun ctio n.
B ON Bra ke Switch Circuit
Malfunctio n1. Thro ttle po sitio n is more
tha n 0%.
2. Engine speed is more than
693rpm (4JA1-TC) or 665
rpm (4JH1-TC).
3. Vehicle speed is more than
0km/h.
4. Brake switch 1 signal and
brake switch 2 signal are
differently inputted to the
ECM.
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
2 1. Connect the Tech 2.
2. Review and record the failure information.
3. Select “F0: Read DTC Infor As Stored By ECU” in
“F0: Diagnostic Trouble Codes”.
Is the DTC P0703 (Symptom Code A) stored as
“Present Failure”?—Go to Step 3Refer to
Diagnostic Aids
and Go to Step
3

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

6E–276 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
8 Repair the open circuit between the “Stop Lamp fuse
(15A)” and brake switch 1.
Is the action complete?—Verify repair—
9 Using the DVM and check the brake switch 1 circuit.
Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type B. (ECM
connected) Ref. Page 6E-103
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 1 and
check the circuit for open or short to voltage
circuit.
Was the problem found?
Pedal is not
stepped on:
Less than 1V
Pedal stepped
on: 10-14.5V Go to Step 12Fix ed at 10-
14.5V: Go to
Step 10
Fix ed at less
than 1V: Go to
Step 11
10 Repair the short to voltage circuit between the brake
switch 1 connector and ECM.
Is the action complete?
—Verify repair—
11 Repair the open circuit between the brake switch 1
connector and ECM.
Is the action complete?
—Verify repair— Step Action Value(s) Yes No
105Breaker Box
V
V
2 C-44
230C-56
C-44
230C-56
C-44

6E–278 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0703 (Symptom Code B) (Flash Code 25)
Brake Switch Circuit Malfunction
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
2 1. Connect the Tech 2.
2. Review and record the failure information.
3. Select “F0: Read DTC Infor As Stored By ECU” in
“F0: Diagnostic Trouble Codes”.
Is the DTC P0703 (Symptom Code B) stored as
“Present Failure”?—Go to Step 3Refer to
Diagnostic Aids
and Go to Step
3
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 B) stored in this
ignition cycle?—Go to Step 4Refer to
Diagnostic Aids
and Go to Step
4
4 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 5
5 Using the DVM and check the brake switch 2.
1. Ignition “Off”, engine “Off”.
2. Remove the brake switch connector at the brake
pedal.
3. Check the brake switch 2.
Was the DVM indicated specified value?
Pedal is not
stepped on:
No continuity
Pedal stepped
on: Continuity Go to Step 6Replace pedal
switch and
verify repair
653
4 C-56 C-44




Brake Switch