Isuzu Trooper (2000 year). Manual - part 259

6E–165

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

DTC P0125 –ECT Excessive Time to Closed Loop Fuel Control

  (Cont'd)

Step

No

Yes

Value(s)

Action

6

Compare engine coolant temperature displayed on the
Tech 2 to the actual coolant temperature measured
with a thermometer.  (Observe normal precautions
when opening the cooling system.)

Is the Tech 2 engine coolant temperature indication
close to the measured temperature?

—

Go to 

Step 9

Go to 

Step 7

7

1. Ignition “OFF.”
2. Disconnect the PCM.
3. Using a DVM, measure the resistance of the ECT at

the PCM connector.

4. Compare the DVM reading with the chart in “Test

Description.”

Is the chart value approximately equal to the
thermometer reading?

—

Go to 

Step 12

Go to 

Step 8

8

Check for high resistance in wiring related to the ECT
sensor.  Also, check for poor connections at the ECT
sensor and the PCM.

Was a problem found?

—

Go to 

Step 10

Go to 

Step 11

9

Refer to 

Cooling and Radiator for cooling system

diagnosis and repair condition as necessary.

Is the action complete?

—

Verify repair

—

10

Replace the faulty terminal(s) or repair faulty wiring as
necessary.

Is the action complete?

—

Verify repair

—

11

Replace the ECT sensor.

Is the action complete?

—

Verify repair

—

12

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed.  Refer to 

On-Vehicle Service in

Powertrain 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 PROGRAMMED
SOFTWARE to the replacement PCM.

Is the action complete?

—

Verify repair

—

6E–166

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code(DTC) 

P0128 Thermostat Insufficient temperrature for Stable Opreation

D06RY00169

Circuit Description

D

The engine coolant temperature (ECT) sensor
thermistor mounted on a coolant crossover pipe at the
front of the engine.

This code determines if system has insufficient
coolant temperatures for stable operation.

Conditions for setting the DTC

D

Engine running.

D

No IAT, ECT and MAF DTCs set.

D

No VSS DTC set.

Warm case(Ambient temperature is between 50

°

F and

128

°

F.):

Time for coolant to reach stabillzed closed loop value is

less than 239 sec.

Cold case(Ambient temperature is between 20

°

F and

50

°

F.):

Time for coolant to reach stabillzed thermostat

regulation temperature is more than 263 sec.

Action Taken When the DTC Sets

D

The PCM will illuminate the malfunction indicator
lamp(MIL) after the second consecutive trip in which
the fault is detected.

D

The PCM will store condition which were present when
the DTC was set as Freeze Frame and in the Failure
Records data.

Conditions for Clearing the MIL/DTC

D

The PCM will turn the MIL “OFF” on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condtion is no longer present.

D

A history DTC P0128 will clear after 40 cosecutive trip
cycle during which the warm up cycles have occurred
without a fault.

D

DTC P0128 can be cleared using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

Tech 2 “Clear Info” function or by disconnecting
the PCM battery feed.

Diagnostic Aids

An intermittent may be caused by the following:

D

Poor connectons.

D

Mis routed harness.

D

Rubbed through wire insulation.

D

Broken wire inside the insulation.

Check for the following conditions:

D

Poor connection at PCM–Inspect harness connectors
for backed out terminals,improper mating,broken
locks, improperly formed or damaged terminals,and
poor terminal

to wire connection.

6E–167

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

D

Damaged harness–Inspect the wiring harness for
damage.

If the harness appears to be OK,observe the ECT
display on the Tech2 while moving connectors and
wiring harnesses related to the sensor.

A change in the display will indicate the location of
the fault.

If DTC P0128 cannot be duplicated, the
information included in the Faillure Records data
can be useful in determined vehicle mileage since
the DTC was last set.

If it is determined that the DTC occurs
intermittently, performing the DTC P0128
Diagnostic Chart may isolate the cause of the
fault.

6E–168

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) 

P0128 Thermostat Insufficient temperrature for stable opreation

 

Step

Action

Value(s)

Yes

No

1

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

—

Go to 

Step 2

Go to 

OBD

System

Check

2

1. Visually/physically check air duct and water pipe for

splits, kinks,and proper conections and routing.

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

Was a problem found?

—

Verify repair

Go to 

Step 3

3

1. Remove and check the filter element for dirt or

restrictions.

2. Replace the air filter element if necessary.

Was a problem found?

—

Verify repair

Go to 

Step 4

4

1. Remove and check the Thermostat for stable

opreation. Refer to 

6B section.

2. Replace the thermostat if necessary.

Was a problem found?

—

Verify repair

Go to 

Step 5

5

1. Ignition “ON”,engine “OFF”.
2. Review and record Tech 2 Failure Records.
3. Opreate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “DTC” info for DTC P0128.

Does the Tech 2 indicate DTC P0128 failed this
ignition?

—

Go to 

Step 6

Refer to 

DiagnosticAid

s

6

1. Ignition “ON”, engine “OFF”.
2. Oberve the “Eng Cool Temp”display on the Tech 2.

Is the “Eng Cool Temp” below the specified value?

139

°

C

(282

°

F)

Verify repair

Go to 

Step 7

7

1. Ignition “OFF”.
2. Disconnect the PCM and check the ECT signal

circuit for a short to ground or a short to the  sensor
ground circuit.

3. If the ECT signal circuit is shorted,repair it as

necessary.

Was a problem found?

—

Verify repair

Refer to 

Diag-

nostic

Go to 

Step 8

8

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 replacement PCM.

Is the action complete?

—

Verify repair

—