Isuzu Trooper (2000 year). Manual - part 235

6E–69

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

A/C Clutch Control Circuit Diagnosis

  (Cont'd)

Step

No

Yes

Value(s)

Action

7

Temporarily substitute the A/C compressor relay in
place of the A/C thermostat relay, then repeat Step 5.

Did the “A/C Request” display indicate “Yes?”

—

Go to 

Step 8

Go to 

Step 9

8

Replace the original A/C thermostat relay.

Is the action complete?

—

Verify repair

—

9

Dose the blower operate?

—

Go to 

Step 10

Go to 

Step 11

10

Repair the blower.

Is the action complete?

—

Verify repair

—

11

Check for a faulty 10A A/C fuse in the underdash fuse
panel.

Was the 10A fuse OK?

—

Go to 

Step 13

Go to 

Step 12

12

Check for short circuit and make repairs if necessary.
Replace the 10A A/C fuse.

Is the action complete?

—

Verify repair

—

13

1. Remove the glove box to gain access to the A/C

thermostat.

2. Disconnect the thermostat connector.
3. Attach a fused jumper between ground and the

PNK/GRN wire at the thermostat.

4. A/C “ON.”
5. Blower “ON.”

Dose A/C request indicate “YES” on the Tech 2?

—

Go to 

Step 14

Go to 

Step 17

14

1. Ignition “ON.”
2. Use a DVM to check voltage at the electronic A/C

thermostat.

Was voltage equal to the specified value?

B+

Go to 

Step 17

Go to 

Step 15

15

Check for an open (LT GRN) between the thermostat
and the A/C switch.

Was the wire open?

—

Go to 

Step 16

Go to 

Step 17

16

Repair the open wire (LT GRN) between the thermostat
and the A/C switch.

Is the action complete?

—

Verify repair

—

17

Check for an open circuit between A/C thermostat relay
and PCM A/C request terminal (F45).

Was there an open circuit?

—

Go to 

Step 18

Go to 

Step 19

18

Repair the open circuit between the PCM and A/C
thermostat relay.

Is the action complete?

—

Verify repair

—

19

1. Ignition “ON.”
2. Use a DVM to check voltage at the A/C pressure

switch (BRN).

Was voltage equal to the specified value?

B+

Go to 

Step 21

Go to 

Step 20

20

Repair the open circuit between the 10A A/C fuse and
the pressure switch.

Is the action complete?

—

Verify repair

—

6E–70

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

A/C Clutch Control Circuit Diagnosis

  (Cont'd)

Step

No

Yes

Value(s)

Action

21

Use an ohmmeter to check continuity between the
pressure switch (GRN/WHT) and the A/C thermostat
relay (GRN/WHT).

Was the circuit open?

—

Go to 

Step 22

Go to 

Step 23

22

Repair the open circuit between the pressure switch
and the A/C thermostat relay.

Is the action complete?

—

Verify repair

—

23

Check for damaged pin or terminal at F45 of the PCM.

Was a damaged pin or terminal found?

—

Go to 

Step 24

Go to 

Step 25

24

Repair the damaged pin or terminal.

Is the action complete?

—

Verify repair

—

25

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed.  Refer to 

On-Vehicle Servicein

Powertrain Control Module Sensors for procedures.

And also refer to latest Service Bulletin.

Check to see if the Latest software is released or not.
And then Down Load the LATEST PROGRAMMED
SOFTWARE to the replacement PCM.

Is the action complete?

—

Verify repair

—

26

1. Remove the A/C compressor relay.
2. Ignition “ON.”
3. Use a DVM to check voltage at both of the BRN

wires at the A/C compressor relay socket.

Is the voltage equal to the specified value?

B+

Go to 

Step 28

Go to 

Step 27

27

Repair the faulty BRN wire between the A/C fuse and
the A/C compressor relay .

Is the action complete?

—

Verify repair

—

28

1. A/C compressor relay removed.
2. Engine idling.
3. A/C “ON.”
4. Blower “ON.”
5. Use a DVM to measure voltage between the

GRN/BLK wire at the A/C compressor relay socket
and battery

±

.

Did the DVM indicate the specified value?

B+

Go to 

Step 32

Go to 

Step 29

29

Check for an open GRN/BLK wire between PCM
terminal F4 and the A/C compressor relay.

Was the wire open?

—

Go to 

Step 30

Go to 

Step 31

30

Repair the open GRN/BLK wire between the PCM and
the A/C compressor relay.

Is the action complete?

—

Verify repair

—

31

Check for a damaged pin or terminal at F4 of the PCM.

Was a damaged pin or a terminal found?

—

Go to 

Step 24

Go to 

Step 25

6E–71

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

A/C Clutch Control Circuit Diagnosis

  (Cont'd)

Step

No

Yes

Value(s)

Action

32

1. A/C compressor relay removed.
2. Connect a fused jumper at the A/C compressor

relay socket between either BRN wire and the
BRN/YEL wire.

3. Engine idling.
4. A/C “ON.”
5. Blower “ON.”

Did the compressor magnetic clutch engage?

—

Go to 

Step 33

Go to 

Step 34

33

Repair the A/C compressor relay.

Is the action complete?

—

Verify repair

—

34

Check for an open circuit between the A/C compressor
relay and the A/C clutch.

Was an open circuit found?

—

Go to 

Step 35

Go to 

Step 36

35

Repair the open circuit between the compressor Clutch
and the A/C compressor relay.

Is the action complete?

—

Verify repair

—

36

Service the compressor clutch or replace the
compressor due to a faulty internal overheat switch.

Is the action complete?

—

Verify repair

—

37

1. Remove the A/C compressor relay.
2. Idle the engine.

Is the compressor clutch still engaged when A/C is not
selected?

—

Go to 

Step 38

Go to 

Step 39

38

Repair the short to voltage between the A/C clutch and
A/C compressor relay.

Is the action complete?

—

Verify repair

—

39

1. Reinstall the A/C compressor relay.
2. Remove the A/C thermostat relay.
3. Engine idling.

Is the compressor clutch still engaged when A/C is not
selected?

—

Go to 

Step 40

Go to 

Step 42

40

Use a DVM to check for a short to ground between the
A/C compressor relay and F4 of the PCM.

Was a short detected?

—

Go to 

Step 41

Go to 

Step 25

41

Repair the short to ground between the PCM and A/C
compressor relay.

Is the action complete?

—

Verify repair

—

42

Repair the short to ground between the A/C thermostat
relay and the electronic thermostat.

Is the action complete?

—

Verify repair

—

6E–72

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Electronic Ignition System Diagnosis

If the engine cranks but will not run or immediately stalls,
the Engine Cranks But Will Not Start chart must be used
to determine if the failure is the ignition system or the fuel
system.  If DTC P0300 through P306, P0341, or P0336 is
set, the appropriate diagnostic trouble code chart must be
used for diagnosis.
If a misfire is being experienced with no DTC set, refer to
the 

Symptoms section for diagnosis.

EVAP Canister Purge Solenoid and

EVAP Vacuum Switch

A continuous purge condition with no purge commanded
by the PCM will set a DTC P1441. Refer to the DTC charts
for further information.

Visual Check of The Evaporative

Emission Canister

D

If the canister is cracked or damaged, replace the
canister.

D

If fuel is leaking from the canister, replace the canister
and check hoses and hose routing.

Fuel Metering System Check

Some failures of the fuel metering system will result in an
“Engine Cranks But Will Not Run” symptom.  If this
condition exists, refer to the 

Cranks But Will Not Run

chart.  This chart will determine if the problem is caused
by the ignition system, the PCM, or the fuel pump
electrical circuit.
Refer to 

Fuel System Electrical Test for the fuel system

wiring schematic.
If there is a fuel delivery problem, refer to 

Fuel System

Diagnosis, which diagnoses the fuel injectors, the fuel
pressure regulator, and the fuel pump.  If a malfunction
occurs in the fuel metering system, it usually results in
either a rich HO2S signal or a lean HO2S signal.  This
condition is indicated by the HO2S voltage, which causes
the PCM to change the fuel calculation (fuel injector pulse
width) based on the HO2S reading.  Changes made to the
fuel calculation will be indicated by a change in the long
term fuel trim values which can be monitored with a
Tech 2.  Ideal  long term fuel trim values are around 0%;
for a lean HO2S signal, the PCM will add fuel, resulting in
a fuel trim value above 0%.  Some variations in fuel trim
values are normal because all engines are not exactly the
same.  If the evaporative emission canister purge is “ON,”
the fuel trim may be as low as –38%.  If the fuel trim values
are greater than +23%, refer to 

DTC P0131, DTC P0151,

DTC P0171, and DTC 1171 for items which can cause a
lean HO2S signal.

Fuel System Pressure Test

A fuel system pressure test is part of several of the
diagnostic charts and symptom checks.  To perform this
test, refer to 

Fuel Systems Diagnosis.

Fuel Injector Coil Test Procedure and
Fuel Injector Balance Test Procedure

T32003

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart:
2. Relieve the fuel pressure by connecting the J

34730-1 Fuel Pressure Gauge to the fuel pressure
connection on the fuel rail.

CAUTION: In order to reduce the risk of fire and
personal injury, wrap a shop towel around the fuel
pressure connection.  The towel will absorb any fuel
leakage that occurs during the connection of the fuel
pressure gauge.  Place the towel in an approved
container when the connection of the fuel pressure
gauge is complete.

Place the fuel pressure gauge bleed hose in an
approved gasoline container.
With the ignition switch “OFF,” open the valve on the
fuel pressure gauge.

3. Record the lowest voltage displayed by the DVM

after the first second of the test.  (During the first
second, voltage displayed by the DVM may be
inaccurate due to the initial current surge.)

Injector Specifications:

Resistance Ohms

Voltage Specification at

10

°

C-35

°

C (50

°

F-95

°

F)

11.8 – 12.6

5.7 – 6.6

D

The voltage displayed by the DVM should be within
the specified range.

D

The voltage displayed by the DVM may increase
throughout the test as the fuel injector windings
warm and the resistance of the fuel injector windings
changes.