Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1268

6E1–148

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DIAGNOSTIC TROUBLE CODE (DTC) P0125 INSUFFICIENT COOLANT TEM-

PERATURE FOR CLOSED LOOP FUEL CONTROL

060R100028

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 sensors.
If the PCM detects that the ECT sensor has not reached a
sufficient reading to achieve ”Closed Loop” within a
specified amount of time, DTC P0125 will set.  DTC
P0125 is a type B code.

Conditions for Setting the DTC

D

No MAP, IAT, ECT, TP, Misfire, Injector,  or VSS DTC
codes set.

Test failed if 3 consective failures detected (500
msec/test).

Warm Case Test

D

Start–up ECT value is less than 29

°

C (84

°

F).

D

IAT is greater than 10

°

C (50

°

F).

D

Accumulated airflow is greater than 1500 grams.

D

Engine run time is greater than 90 seconds.

D

Time for coolant to reach stabilized ”Closed Loop”
value is less than 120 seconds.

Cold Case Test

D

IAT is between –7

°

C (20

°

F) and 10

°

C (50

°

F)

D

Accumulated airflow is greater than 2000 grams.

D

Engine run time is less than 225 seconds.

D

Time for coolant to reach stabilized ”Closed Loop”
value is less than 300 seconds.

Other Case Test

D

IAT is between –30

°

C (–22

°

F) and –7

°

C (20

°

F).

D

Accumulated airflow is greater than 3600 grams.

D

Engine run time is less than 450 seconds.

D

Time for coolant to reach stabilized ”Closed Loop”
value is less than 600 seconds.

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 conditions which were present
when the Diagnostic Trouble Code 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 condition is no longer present.

6E1–149

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

D

A history Diagnostic Trouble Code P0125 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.

D

Diagnostic Trouble Code P0125 can be cleared by
using the Scan Tool’s ”Clear Info” function. 

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:

D

Poor connection at PCM – Inspect harness connectors
for back–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; open circuits, shorts to ground, or shorts to
voltage. 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 since 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 closed, the fault is intermittent;
refer to Diagnostic Aids. 

7. Engine Coolant Temperature

°

C

°

F

OHMS

Temperature vs. Resistance Values (approximate)

100

212

177

80

176

332

60

140

667

45

113

1188

35

95

1802

25

77

2796

15

59

4450

5

41

7280

–5

23

12300

–15

5

21450

–30

–22

52700

–40

–40

100700

DTC P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control

 

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 ECT sensor DTC’s set?

—

Go to

applicable

ECT sensor

DTC chart

Go to Step 3 

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 

4

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?

21

°

C (70

°

F)

Refer to

Diagnsotic

Aids 

Go to Step 5 

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 

6E1–150

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DTC P0125 Insufficient Coolant Temperature for 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 the following conditions in the wiring between
the ECT and the PCM:

D

An open circuit

D

A short to ground

D

A short to voltage

—

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

—

6E1–151

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Diagnostic Trouble Code(DTC) P0128 Thermostat Insufficient temperrature for

Stable Opreation

060R100028

Circuit Description

To provide the best possible combination of driveability,
fuel economy, and emission control, a “closed loop”
air/fuel metering system used. When the vehicle is first
started, the power train control module (PCM) controls
fuel delivery in “open loop” ignoring the heated oxygen
sensor (HO2S) signals and caculating air/fuel ratio based
on inputs from the engine coolant temperature and
throttle position sensors.
This DTC will detect an open thermostat that causes the
engine coolant temperature not reaching the warm-up
temperature within the specified value. It is Type B code.

Conditions for setting the DTC

Cold Case:

D

Engine starting temperature more than –7

°

C (20

°

F)

and less than 10

°

C (50

°

F).

D

The accumulated airflow more than 10000 g.

D

The accumulated idle time less than 450 seconds.

D

Time for coolant temperature must be 74

°

C after 800

seconds.

Warm Case:

D

The accumulated idle time is less than 255 seconds.

D

The starting temperature is between –7

°

C (19

°

F) and

37

°

C (99

°

F).

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: