Isuzu Trooper (1998-2002 year). Manual - part 625

6E–148

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P1487 (Flash DTC 73)

Intake Throttle System Circuit Open/Start

060RW134

Circuit Description

The intake throttle position (ITP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle.

Action Taken When the DTC Sets

The ECM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

The ECM 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

DTC P1487 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the ECM battery
feed.

Diagnostic Aids

Check for the following conditions:

Poor connection at ECM – 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
throttle position display on the Tech 2 while moving
connectors and wiring harnesses related to the ITP
sensor. A change in the display will indicate the
location of the fault.

If DTC P1487 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

6E–149

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

DTC P1487 – Intake Throttle System Circuit Open/Short

Step

Action

Value(s)

Yes

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

—

Go to

Step 2

Go to

OBD

System

Check

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

conditions as noted.

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

P1487.

Does the Tech 2 indicate DTC P1487 failed?

—

Go to

Step 3

Refer to

Diagnostic

Aids

Check the ITP circuit for a poor connection at the ECM
and ITP and replace the terminal if necessary.

Did the terminal require replacement?

—

Verify repair

Go to

Step 4

1. Ignition “ON,” engine “OFF.”
2. Operate the throttle by the hand.

Is the action complete?

—

Verify repair

Go to

Step 5

Replace the ITP Assembly.

Is the action complete?

—

Verify repair

Go to

Step 6

Replace the ECM (Refer to the Data Programming in
Case of ECM change).

Is the action complete?

—

Verify repair

—

6E–150

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P1488 (Flash DTC 72)

Intake Throttle Motor Control Circuit Signal Gap

060RW135

Circuit Description

The Intake throttle position (ITP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle.

Action Taken When the DTC Sets

The ECM 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

DTC P1488 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the ECM battery
feed.

Diagnostic Aids

Check for the following conditions:

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

If DTC P1488 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

6E–151

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

DTC P1488 – Intake Throttle Motor Control Circuit Signal Gap

Step

Action

Value(s)

Yes

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

—

Go to

Step 2

Go to

OBD

System

Check

1. Ignition “ON,” engine “OFF.”
2. With the throttle closed, observe the “ITP Sensor”

display on the Tech 2.

Is the “ITP Sensor” below the specified value?

0.22 V

Go to

Step 4

Go to

Step 3

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

conditions as noted.

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

DTC P1488.

Does the Tech 2 indicate DTC P1488 failed?

—

Go to

Step 4

Refer to

Diagnostic

Aids

Check the ITP circuit for a poor connection at the ECM
and replace the terminal if necessary.

Did the terminal require replacement?

—

Verify repair

Go to

Step 5

Check the Intake throttle motor circuit for a poor
connection and replace the terminal if necessary.

Did the terminal require replacement?

—

Verify repair

Go to

Step 6

Check the ITP Assembly for a poor connection at the
TP sensor and fasten the ITP Assembly if necessary.

Did the ITP Assembly require repair?

—

Verify repair

Go to

Step 7

Replace the ECM (Refer to the Data Programming in
Case of ECM change).

Is the action complete?

—

Verify repair

—

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