Isuzu Trooper (2000 year). Service manual - part 234

6E–65

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

On-Board Diagnostic (OBD II) System Check

 

Step

Action

Value(s)

Yes

No

1

1.  Ignition “ON,”engine “OFF.”
2.  Observe the malfunction indicator lamp (MIL or

“Check Engine lamp”).

Is the MIL (“Check Engine lamp”)“ON?”

—

Go to 

Step 2

Go to 

No

MIL(“Check

Engine lamp”)

2

1.  Ignition “ON,”engine “OFF.”
2.  Observe the malfunction indicator lamp (“Reduced

Power lamp”).

Is the MIL (“Reduced Power lamp”) “ON?”

—

Go to 

Step 3

Go to 

No

RPL(“Reduce

d Power

lamp”)

3

1. Ignition “OFF.”
2. Install Tech 2.
3. Ignition “ON.”
4. Attempt to display PCM engine data with the

Tech 2.

Does the Tech 2 display PCM data?

—

Go to 

Step 4

Go to 

Step 12

4

1.  Using the Tech 2 output tests function, select MIL

(“Check Engine lamp”) control and   command the
MIL (“Check Enginelamp”) “OFF.”

2.  Observe the MIL (“Check Engine lamp”).

Did the MIL (“Check Engine lamp”) turn “OFF?”

—

Go to 

Step 5

Go to

MIL(“Check

Engine lamp”)

On Steady

5

1.  Using the Tech 2 output tests function, select MIL

(“Reduced Power lamp”) control and   command the
MIL (“Reduced Power lamp”) “OFF.”

2.  Observe the MIL (“Reduced Power lampp”).

Did the MIL (“Reduced Power lamp”) turn “OFF?”

—

Go to 

Step 6

Go to

RPL(“Reduce

d Power

lamp”)On

Steady

6

Select “Display DTCs” with the Tech 2.

Are any DTCs stored?

—

Go to 

Step 7

Go to 

Step 11

7

Following  below the DTCs stored:
P0562,P0563,P0601,P0602,P0604,P0606,P1625,P1
635,P1639,P1640, 1650

—

Go to

applicable
DTC table

Go to 

Step 8

8

Following  below the DTCs stored:
P1514, P1515, P1516, P1523, P1125, P1290, P1295,
P1299

—

Go to

applicable
DTC table

Go to 

Step 9

9

Following  below the DTCs stored:

1.  P0425, P0106, P0107, P1107, P0401, P1404,

P0405, P1120, P1221, P1515, P1516, P1275,
P1635, P1271, P1273, P1285, P1272

2.

P0336,P0337,P0341,P0342,P1220,P1515,P1221,
 P1516,P1280,P1639,P1271,P1272

—

Go to

“Multiple

PCM

Information

sensor DTCs

Set”

Go to 

Step 10

10

Attempt to start the engine.

Did the engine start and continue to run?

—

Go to 

Step 6

Go to 

Cranks

But Will Not

Run

6E–66

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

On-Board Diagnostic (OBD II) System Check

  (Cont'd)

Step

No

Yes

Value(s)

Action

11

Compare PCM data values displayed on the Tech 2 to
the typical engine scan data values.

Are the displayed values normal or close to the typical
values?

—

Go to

Symptom

Refer to

indicated

Component

System
Checks

12

1.  Ignition “OFF,” disconnect the PCM.
2.  Ignition “ON,” engine “OFF.”
3.  Check the Class 2 data circuit for an open, short to

ground, or short to voltage. Also, check the DLC
ignition feed circuit for an open or short to ground
and the DLC ground circuit for an open.

4.  If a problem is found, repair as necessary.

Was a problem found?

—

Go to 

Step 2

Go to 

Step 13

13

1.  Attempt to reprogram the PCM. Refer to 

Powertrain

 Control Module (PCM) in On-Vehicle Service.

2.  Attempt to display PCM data with the Tech 2.

Does the Tech 2 display PCM engine data?

—

Go to 

Step 2

Go to 

Step 14

14

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed. Refer to 

ON-Vehicle Service in Power

Control Module and 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 PROGRMMED SOFTWARE to the
replasement PCM.

Is the action complete?

—

Go to 

Step 2

—

6E–67

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

A/C Clutch Control Circuit Diagnosis

D06RY00159

Circuit Description

When air conditioning 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
powertrain control module (PCM).  The A/C request
signal may be temporarily canceled during system
operation by the electronic thermostat in the evaporator
case. When the A/C request signal is received by the
PCM, the PCM supplies a ground from the compressor
clutch relay if the engine operating conditions are within
acceptable ranges.  With the A/C compressor relay
energized, voltage is supplied to the compressor clutch
coil.
The PCM will enable the compressor clutch to engage
whenever A/C has been selected with the engine running,
unless any of the following conditions are present:

D

The throttle is greater than 90%.

D

The ignition voltage is below 10.5 volts.

D

The engine speed is greater than 4500 RPM for 5
seconds or 5400 RPM.

D

The engine coolant temperature (ECT) is greater
than 125 

°

C (257 

°

F).

D

The intake air temperature (IAT) is less than 5

°

C

(41

°

F).

D

The power steering pressure switch signals a high
pressure condition.

Diagnostic Aids

To diagnose an the intermittent fault, check for following
conditions:

D

Poor connection at the PCM–Inspect connections for
backed-out terminals, improper mating, broken locks,
improperly formed or damaged terminals, and poor
terminal-to-wire connection.

D

Damaged harness–Inspect the wiring harness for
damage.  If the harness appears to OK, observe the
A/C clutch while moving connectors and wiring
harnesses related to the A/C.  A sudden clutch
malfunction will indicate the source of the intermittent
fault.

6E–68

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

A/C Clutch Diagnosis

This chart should be used for diagnosing the electrical
portion of the A/C compressor clutch circuit.  A Tech 2 will
be used in diagnosing the system.  The Tech 2 has the
ability to read the A/C request input to the PCM.  The
Tech 2 can display when the PCM has commanded the
A/C clutch “ON.”  The Tech 2 should have the ability to
override the A/C request signal and energize the A/C
compressor relay.

Test Description

IMPORTANT:

Do not engage the A/C compressor

clutch with the engine running if an A/C mode is not
selected at the A/C control switch.
The numbers below refer to the step numbers on the
Diagnostic Chart:

3. This a test determine is the problem is with the

refrigerant system.  If the switch is open, A/C
pressure gauges will be used to determine if the
pressure switch is faulty or if the system is partially
discharged or empty.

4. Although the normal complaint will be the A/C clutch

failing to engage, it is possible for a short circuit to
cause the clutch to run when A/C has not been
selected.  This step is a test for that condition.

7. There is an extremely low probability that both relays

will fail at the same time, so the substitution process
is one way to check the A/C Thermostat relay.  Use
a known good relay to do a substitution check.

A/C Clutch Control Circuit Diagnosis

 

Step

Action

Value(s)

Yes

No

1

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to 

Step 2

Go to 

OBD

System

Check

2

Are any other DTCs stored?

—

Go to the

other DTC

chart(s) first

Go to 

Step 3

3

1. Disconnect the electrical connector at the pressure

switch located on the receiver/drier.

2. Use an ohmmeter to check continuity across the

pressure switch.

Is the pressure switch open?

—

Go to Air

Conditioning

to diagnose

the cause of

the open
pressure

switch

Go to 

Step 4

4

IMPORTANT: Before continuing with the diagnosis, the
following conditions must be met:

D

The intake air temperature must be greater than
15

°

C. (60

°

F).

D

The engine coolant temperature must be less
than 119

°

C (246

°

F).

1. A/C “OFF.”
2. Start the engine and idle for 1 minute.
3. Observe the A/C compressor.

Is the A/C compressor clutch engaged even though
A/C has not been requested?

—

Go to 

Step 37

Go to 

Step 5

5

1. Idle the engine.
2. A/C “ON”.
3. Blower “ON”.
4. Observe the A/C compressor.

Is the A/C compressor magnetic clutch engaged?

—

Refer to

Diagnostic

Aids

Go to 

Step 6

6

1. Engine idling.
2. A/C “ON”.
3. Blower “ON”.
4. Observe the “A/C Request” display on the Tech 2.

(Refer to the Miscellaneous test)

Does the tool “A/C Request” display indicate “Yes?”

—

Go to 

Step 26

Go to 

Step 7