Content .. 781 782 783 784 ..

Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 783

6E–156

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

DTC P0118 – ECT Sensor Circuit High Voltage

(Cont'd)

Step

Yes

Value(s)

Action

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

ground circuit for an open.

3. If the ECT sensor ground circuit is open, repair it as

necessary.

Was the ECT sensor ground circuit open?

—

Verify repair

Go to

Step 9

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

circuit for an open.

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

necessary.

Was the ECT signal circuit open?

—

Verify repair

Go to

Step 9

Check for a poor sensor ground or ECT signal circuit
terminal connection at the PCM and replace
terminal(s) if necessary.

Did any of the terminals need to be replaced?

—

Verify repair

Go to

Step 11

Replace the ECT sensor.

Is the action complete?

—

Verify repair

—

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–157

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC)

P0125 ECT Excessive Time to Closed Loop Fuel Control

D06R200049

Circuit Description

To provide the best possible combination of driveability,
fuel economy, and emission control, a “closed loop”
air/fuel metering system is used. When the vehicle is first
started, the powertrain control module (PCM) controls
fuel delivery in “open loop”, ignoring the heated oxygen
sensor (HO2S) signals and calculating air/fuel ratio based
on inputs from the engine coolant temperature, throttle
position, and mass air flow sensors. The PCM will begin
using the Bank 1 HO2S 1 and Bank 2 HO2S 1 signals for
controlling fuel delivery under “closed loop” conditions
when the following conditions have been met:

The HO2S output signals are varying, indicating that
the sensors are hot enough to operate properly.

The engine coolant temperature sensor indicates
coolant temperature above 50

C (122

F).

Time since start-up is at least 16 seconds for a warm
engine or 23 seconds for a cold engine.

Conditions for Setting the DTC

No active IAT, MAF or ECT DTC(s) are present.

Engine is running.

Vehicle speed is greater than 5 mph (8 km/h) .

Intake air temperature is greater than –10

C (14

C (32

F).

Start–up engine coolant temperature is between
–10

C (–14

F) and 28

C (82

F).

For a warm engine (intake air temperature is greater
than 10

C/50

F), engine coolant temperature

sufficient to allow “closed loop” operation
(50

C/122

F) is not achieved within 2 minutes of

start-up. For a cold engine (intake air temperature
between (–7

C and 10

C), engine coolant

temperature sufficient to allow “closed loop” operation
(50

C/122

F) is not achieved within 10 minutes of

start-up.

The above condition fails 20 consecutive times.

Action Taken When the DTC Sets

The PCM will ON the MIL after second trip with
detected fault.

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

Conditions for Clearing the MIL/DTC

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

A history DTC P0125 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P0125 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

6E–158

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Aids

DTC P0125 set indicates a faulty ECT sensor.
Comparing the engine coolant temperature displayed on
a Tech 2 with actual coolant temperature measured with a
thermometer may isolate this condition. If the displayed
engine coolant temperature is not close to the actual
coolant temperature, replace the ECT sensor.
Check for the following conditions:

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.

Damaged harness – Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
display on the Tech 2 while moving connectors and
wiring harnesses related to the sensor. A change in the
display will indicate the location of the fault.

If DTC P0125 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage wince the DTC was last set.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Comparing the engine coolant temperature displayed

on a Tech 2 with actual coolant temperature
measured with a thermometer may isolate this
condition. If the displayed engine coolant
temperature is not close to the actual coolant
temperature, replace the ECT sensor. If the
temperatures are close, the fault is intermittent;
refer to

Diagnostic Aids.

Engine Coolant Temperature

OHMS

Temperature vs. Resistance Values

(approximate)

100

212

177

176

332

140

667

113

1188

1802

2796

4450

7280

–5

12300

–15

21450

–30

–22

52700

–40

100700

DTC P0125 –ECT Excessive Time to Closed Loop Fuel Control

Step

Action

Value(s)

Yes

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

—

Go to

Step 2

Go to

OBD

System

Check

Are any ECT sensor DTCs set?

—

Go to

applicable

ECT sensor

DTC chart

Go to

Step 3

1. Allow the engine to cool completely.
2. Check the cooling system coolant level (refer to

Cooling and Radiator).

Is the coolant level OK?

—

Go to

Step 4

Go to

Step 9

1. Start the engine.
2. With the engine idling, monitor “ENG COOL TEMP”

display on the Tech 2.

Does “ENG COOL TEMP” increase to above the
specified value within 2 minutes?

C (70

Check the

Procedure

Refer to

Diagnostic

Aids

Go to

Step 5

Check for proper operation of the thermostat (refer to
Cooling and Radiator).

Is the thermostat operating correctly?

—

Go to

Step 6

Go to

Step 9

6E–159

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

DTC P0125 –ECT Excessive Time to Closed Loop Fuel Control

(Cont'd)

Step

Yes

Value(s)

Action

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

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

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

Refer to

Cooling and Radiator for cooling system

diagnosis and repair condition as necessary.

Is the action complete?

—

Verify repair

—

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

Is the action complete?

—

Verify repair

—

Replace the ECT sensor.

Is the action complete?

—

Verify repair

—

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

—

Content .. 781 782 783 784 ..