2007 ISUZU KB P190 heater

ENGINE MECHANICAL 6A – 41

















































Coolant Replenishment
Warning:
When the coolant is heated to a high temperature, be
sure not to loosen or remove the rediator cap.
Otherwise you might get scalded by hot vapor or
boiling water.
To open the radiator cap, put a piece of thick cloth on
the cap and loosen the cap slowly to reduce the
pressure when the coolant has become cooler.
1. Open rediator cap pour coolant up to filler neck
2. Pour coolant into reservoir tank up to "MAX" line
3. Tighten radiator cap and start the engine. After idling for 2 to 3 minutes, stop the engine and reopen radiator
cap. If the water level is lower, replenish.
4. After replenish the coolant tighten radiator cap, warm up the engine at about 2000 rpm. Set heater
adjustment to the highest temperature position, and let
the coolant circulate also into heater water system.
5. Check to see the thermometer, continuously idling 5 minutes and stop the engine.
6. W hen the engine has been cooled, check filler neck for water level and replenish if required. Should extreme
shortage of coolant is found, check the coolant system
and reservoir tank hose for leakage.
7. Pour coolant into the reservoir tank up to "MAX" line.
Coolant Capacity lit (US/UK gal)

4JA1 / TC 9.4 (2.5 / 2.1)
4JH1TC M/T: 10.1 (2.7 / 2.2)
A/T: 10.0 (2.6 / 2.2)
























Engine Warm-Up
After completing the required maintenance procedures,
start the engine and allow it to idle until it is warm.
Check the following:
1. Engine idling speed.
2. Engine noise level.
3. Engine lubricating system and cooling system. Carefully check for oil and coolant leakage.
4. Clutch engagement.
5. Transmission operation.
6. Indicator warning light operation.



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ISUZU KB P190 2007

ENGINE COOLING 6B – 9
• After tightening radiator cap, warm up the engine at about
2000 rpm. Set heater adjustment to the highest temperature
position, and let the coolant circulate also into heater wate
r
system.
• Check to see the thermostat has opened through the
needle position of water thermometer, conduct a 5–minute
idling again and stop the engine.
• W hen the engine has been cooled, check filler neck fo
r
water level and replenish if required. Should extreme
shortage of coolant is found, check the cooling system and
reservoir tank hose for leakage.
• Pour coolant into the reservoir tank up to “MAX" line.


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ISUZU KB P190 2007

6E-242 Engine Control System (4JH1)
DTC A/C Compressor System Check
Description
W hen air conditioning (A/C) and blower fan are
selected, and if the system has a sufficient refrigerant
charge. A 12-volt signal is supplied to the A/C request
input of the Engine Control Module (ECM). The A/C
request signal may be temporarily canceled during
system operation by the electronic thermostat in the
evaporator to prevent the evaporator icing. Also, it is
cancelled when the pressure switch detected abnormal
pressure in the line. W hen the A/C request signal is
received by the ECM, the ECM supplies a ground from
the A/C compressor relay if the engine operating
conditions are within acceptable ranges. W ith the A/C
compressor relay energized, voltage is supplied to the
compressor clutch coil. The ECM will enable the
compressor clutch to engage whenever A/C has been
selected with the engine running and enable conditions
are met.
Condition for Running the A/C Compressor:
• The engine is running.
• The A/C switch is ON.
• The engine coolant temperature (ECT) is less than
105 °C(221 °F).

A/C Compressor System Check
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Chart 1 of 2
Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check-
Engine Controls? 
Go to Step 2 Go to Diagnostic
System Check – Engine Controls
2 1. Install the scan tool. 2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Monitor the Diagnostic Trouble Code (DTC) Information of the engine control system with the
scan tool and check whether following DTC(s) is
set: • P0115 (Symptom Code 1 & 2)
• P0645 (Symptom Code 4 & 8)
Are any of the above DTC(s) set? 

Refer to Applicable DTC Go to Step 3
3 1. Turn ON the ignition, with the engine OFF.
2. Turn ON the blower motor switch.
Does the blower motor turn ON and operate
correctly? 

Go to Step 4 Refer to Applicable
Diagnostic Chart in Heating & Air Conditioning Section
4 1. Turn OFF the blower motor switch. 2. Keep the A/C switch OFF.
Does the A/C Request Signal parameter indicate
OFF? 

Go to Step 5 Go to Chart 2 of 2
with heater Step 1 OR
Go to Chart 2 of 2
without heater Step 1
5 1. Start the engine and let the engine idle. 2. Keep the blower motor switch OFF.
3. Keep the A/C switch OFF.
Does the A/C compressor clutch keep OFF
(disengage)? 

Go to Step 6 Go to Step 11
6 1. Turn ON the blower motor switch. 2. Keep the A/C switch OFF.
Does the A/C compressor clutch keep OFF
(disengage)? 

Go to Step 7 Go to Chart 2 of 2
with heater Step 7 OR
Go to Chart 2 of 2
without heater Step 4

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-243
Step Action Value(s) Yes No
7 1. Turn OFF the blower motor switch.
2. Turn ON the A/C switch.
Does the A/C compressor clutch keep OFF
(disengage)? 

Go to Step 8 Go to Chart 2 of 2
with heater Step 8 OR
Go to Chart 2 of 2
without heater Step 10
8 1. Turn ON the blower motor switch. 2. Keep the A/C switch ON.
Does the A/C compressor clutch ON and OFF
(engage and disengage) periodically within the
Condition for Running the A/C Compressor? 

Go to Step 9 Go to Step 10
9 Does the air flow cool enough. 
System OK Refer to Applicable
Diagnostic Chart in Heating & Air Conditioning Section
10 Does the A/C Relay Command parameter indicate ON at previous step?

Go to Step 14 Go to Chart 2 of 2
with heater Step 9 OR
Go to Chart 2 of 2
without heater Step 11
11 1. Turn OFF the ignition. 2. Disconnect the A/C compressor clutch harness connector (E-3).
3. Start the engine.
Does the A/C compressor clutch ON (engage)? 

Go to Step 22 Go to Step 12
12 1. Turn OFF the ignition. 2. Remove the A/C compressor relay from the engine room relay block.
3. Connect a test lamp between the A/C compressor clutch voltage supply circuit (pin 2 of
X-14 connector) and a known good ground.
4. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate? 

Go to Step 13 Go to Step 21
13 Repair the short to battery or ignition voltage on the A/C compressor voltage feed circuit between the
A/C compressor relay (pin 2 of X-14 connector) and
the A/C compressor (E-3).
Did you complete the repair? 

Go to Step 23 
14 1. Turn OFF the ignition.
2. Remove the A/C compressor relay from the engine room fuel block.
3. Connect a test lamp between the voltage feed circuit of the relay switch side terminal (pin 1 of
X-14 connector) and known good ground.
4. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate? 

Go to Step 15 Go to Step 17
15 1. Keep the ignition ON, with the engine OFF. 2. Disconnect the test lamp.
3. Connect a 3-amp fused jumper wire between both switch side terminals of the A/C compressor
relay (pins 1 and 2 of X-14 connector).
Does the A/C compressor clutch click (engage)? 

Go to Step 19 Go to Step 16

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ISUZU KB P190 2007

6E-244 Engine Control System (4JH1)
Step Action Value(s) Yes No
16 1. Keep the ignition ON, with the engine OFF.
2. Keep 3-amp fused jumper wire with connected.
3. Disconnect A/C compressor clutch harness connector.
4. Connect a test lamp between A/C compressor voltage feed circuit (E-3) and a known good
ground.
Does the test lamp illuminate? 

Go to Step 20 Go to Step 18
17 Repair the open circuit or high resistance on the relay switch side voltage feed circuit between the
A/C compressor relay (pin 1 of X-14 connector) and
the A/C (10A) fuse (EB-13).
Did you complete the repair? 

Go to Step 23 
18 Repair the open circuit or high resistance on the
relay switched voltage supply circuit between the
A/C compressor relay (pin 2 of X-14 connector) and
the A/C compressor clutch (pin 1 of E-3 connector).
Did you complete the repair? 

Go to Step 23 
19 1. Turn OFF the ignition.
2. Inspect for an intermittent and for poor connections at the A/C compressor relay
terminals (pins 3 and 5 of X-14 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 23 Go to Step 21
20 1. Turn OFF the ignition. 2. Inspect for an intermittent and for a poor connection at the harness connector of the A/C
compressor clutch (E-3).
3. Repair the connection(s) as necessary.
Did you find and correct the condition? 

Go to Step 23 Go to Step 22
21 Replace the A/C compressor relay. Did you complete the replacement? 

Go to Step 23 
22 Replace the A/C compressor. Refer to Heating and
Air Conditioning section.
Did you complete the replacement? 

Go to Step 23 
23 1. Reconnect all previously disconnected fuse,
relay or harness connector(s).
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Turn ON the blower motor switch.
Does the blower motor turn ON and operate
correctly? 

Go to Step 4 Refer to Applicable
Diagnostic Chart in Heating & Air Conditioning Section

Chart 2 of 2 with heater
Step Action Value(s) Yes No
1 1. Turn OFF the ignition.
2. Replace the thermo relay with the horn relay or replace with a known good relay.
3. Turn OFF the blower motor switch.
4. Turn OFF the A/C switch.
5. Turn ON the ignition, with the engine OFF.
Does the A/C Request Signal parameter indicate
OFF? 

Go to Step 33 Go to Step 2

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ISUZU KB P190 2007

Engine Control System (4JH1) 6E-249
Step Action Value(s) Yes No
39 1. Reconnect all previously disconnected fuse,
relay or harness connector(s).
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Turn ON the blower motor switch.
Does the blower motor turn ON and operate
correctly? 

Go to Char 1 of 2 Step 4 Refer to Applicable
Diagnostic Chart in Heating & Air Conditioning Section

Chart 2 of 2 without heater
Step Action Value(s) Yes No
1 1. Turn OFF the ignition.
2. Replace the thermo relay with the horn relay or replace with a known good relay.
3. Turn OFF the blower motor switch.
4. Turn OFF the A/C switch.
5. Turn ON the ignition, with the engine OFF.
Does the A/C Request Signal parameter indicate
OFF? 

Go to Step 37 Go to Step 2
2 1. Turn OFF the ignition. 2. Remove the thermo relay from the engine room relay block.
3. Turn ON the ignition, with the engine OFF.
Does the A/C Request Signal parameter indicate
OFF? 

Go to Step 3 Go to Step 5
3 1. Turn OFF the ignition. 2. Reinstall the thermo relay.
3. Remove the radiator grille in order to access the pressure switch.
4. Disconnect the pressure switch harness connector (C-24).
5. Turn OFF the blower motor switch.
6. Turn OFF the A/C switch.
7. Turn ON the ignition, with the engine OFF.
Does the A/C Request Signal parameter indicate
OFF? 

Go to Step 7 Go to Step 6
4 1. Turn OFF the ignition. 2. Remove the glove box in order to access the electronic thermostat.
3. Back probe a test lamp between the electronic thermostat harness (pin 2 of C-55 connector) and
battery voltage.
4. Turn ON the blower motor switch.
5. Turn OFF the A/C switch.
6. Keep the ignition OFF.
Does the test lamp illuminate? 

Go to Step 8 Go to Step 9
5 Repair the short to battery or ignition voltage on the thermo relay signal input circuit between the thermo
relay (pin 1 of X-15 connector) and the engine
control module (ECM) (pin 33 of C-56 connector).
Did you complete the repair? 

Go to Step 43 
6 Repair the short to ground between the thermo relay
(pin 5 of X-15 connector) and pressure switch (pin 1
of C-24 connector).
Did you complete the repair? 

Go to Step 43 

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ISUZU KB P190 2007

ENGINE COOLING (4JK1/4JJ1) 6B-7
Draining and Refilling Cooling System
Before draining the cooling system, inspect the system
and perform any necessary service to ensure that it is
clean, does not leak and is in proper working order.
The engine coolant (EC) level should be between the
“MIN" and “MAX" lines of the reserve tank when the
engine is cold. If low, check for leakage and add EC up
to the “MAX" line.
There should not be any excessive deposit of rust o
r
scales around the radiator cap or radiator filler hole, and
the EC should also be free from oil.
Replace the EC if excessively dirty.

1. Remove the radiator skid plate.
2. Completely drain the cooling system by opening the drain plug at the bottom of the radiator.




RTW 56BSH000301
3. Remove the radiator cap.
WARNING:
To avoid the danger of being burned, do not
remove the cap while the engine and radiator are
still hot. Scalding fluid and steam can be blown out
under pressure.
4. Disconnect all hoses from the EC reserve tank.
Scrub and clean the inside of the reserve tank with soap and water. Flush it well with clean water,
then drain it. Install the reserve tank and hoses.

5. Refill the cooling system with the EC using a
solution that is at least 50 percent antifreeze.

Procedure for filling with coolant (in case of full change).
• Make sure that the engine is cool.
• Open radiator cap and pour coolant up to fille
r
neck.
• Pour coolant into reservoir tank up to “MAX" line.
• Tighten radiator cap and start the engine. Afte
r
idling for 2 to 3 minutes, stop the engine and
reopen the radiator cap. If the water level is lower,
replenish.
WARNING:
When the coolant is heated to a high temperature,
be sure not to loosen or remove the radiator cap.
Otherwise you might get scalded by hot vapor o
r
boiling water. To open the radiator cap, put a piece
of thick cloth on the cap and loosen the cap slowly
to reduce the pressure when the coolant has
become cooler.
• After tightening the radiator cap, warm up the
engine at about 2000 rpm. Set heater adjustment
to the highest temperature position, and let the
coolant circulate also into heater water system.
• Check to see the thermostat has opened through
the needle position of the water thermometer,
conduct a 5–minute idling again and stop the
engine.
• W hen the engine has been cooled, check fille
r
neck for water level and replenish if required.
Should extreme shortage of coolant be found,
check the cooling system and reservoir tank hose
for leakage.
• Pour coolant into the reservoir tank up to “MAX"
line.

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ISUZU KB P190 2007

6E-10 ENGINE CONTROL SYSTEM (4JK1/4JJ1)
Engine Controls Schematics
Power Distribution (1)
RTW76EXF003601
X-11
X-11 Heater
relay
1
2
Blower
motor Ignition
switchIgnition
switch Starter
relay
SBF1
Main
120A SBF2
ABS-1
40A SBF3
ABS-2
20A SBF5
IG1
40A SBF4
ECM
40A
SBF6
Blower
30A
EB-13
A/C
10A
2
BLU/
RED
3
BLU/
RED 3
BLU/
RED SBF8
Glow
60A
SBF7
Front
Fog
20A
SBF9
IG2
60A
EB-9
Fog
15A
or
Trailer
20AEB-10
Tail/Illumi
10A
or
Condenser
fan
20A EB-4
Engine
10A
EB-14
4WD
10A EB-15
Horn
10A EB-16
Hazard10A EB-1
ACG
(S)
10AEB-2
ECM
(B)
10AEB-3
F/Pump10A
EB-5 H/L HI(RH)10A Fuse
EB-6 H/L HI(LH)10A Fuse
EB-7 H/L LO(RH)10A Fuse
EB-8 H/L LO(LH)10A Fuse
P-6
Body
Generator P-5
8 BLK/
P-1
P-2
Battery
8
BLK 5WHTSrarter
Srarter
C-3
ELEC IG
10A
Fuse
E-92
0.5 WHT
0.3
BLK 3
WHT/
RED 5
WHT
0.3
BLK 5
RED/
BLU
5
RED
3
WHT/
BLK
30
BLK/
RED
30
BLK/
YEL
P-10
Engine
5
4 X-12
X-12
ECM
Fuel pump relay
ECM
ECM
main
relay
1
2 5
4
X-6
X-6
2
RED/
WHT
0.3
RED/
BLU Fuse/ relay box(Engine room)
2
RED
2
RED
0.5
RED
2
WHT
2
RED/
BLU 2
WHT
2
3 1
5
Lighting
switch Head
lamp
relay
C-36 C-36
RED
P-16
P-15
2nd
Battery
30
BLK/
YEL 30
BLK/
RED
P-10

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