Isuzu Trooper (1998-2002 year). Manual - part 494

6E–346

6VE1 3.5 ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC)

P1115 ECT Sensor Circuit Intermittent High Voltage

D06R200049

Circuit Description

The engine coolant temperature (ECT) sensor is a
thermistor mounted in the engine coolant stream. The
powertrain control module (PCM) applies a voltage
(about 5.0 volts) through a pull-up resistor to the ECT
signal circuit. When the engine coolant is cold, the sensor
(thermistor) resistance is high, therefore the PCM will
measure a high signal voltage. As the engine coolant
warms, the sensor resistance becomes less, and the
ECT signal voltage measured at the PCM drops. With a
fully warmed up engine, the ECT signal voltage should
measure about 1.5 to 2.0 volts. If the PCM detects an
ECT signal that is intermittently above the range of the
ECT sensor, DTC P1115 will set.

Conditions for Setting the DTC

Engine running time longer than 90 seconds.

The ECT sensor signal is intermittently greater than
–39

C (–38

F) (about 5 volts) for a total of 10 seconds

over a 100-second period.

Action Taken When the DTC Sets

The PCM will not illuminate the malfunction indicator
lamp (MIL).

The PCM will store conditions which were present
when the DTC was set as Failure Records data only.
This information will not be stored as Freeze Frame
data.

Conditions for Clearing the MIL/DTC

A history DTC P1115 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P1115 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

Diagnostic Aids

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
ECT display on the Tech 2 while moving connectors
and wiring harnesses related to the ECT sensor. A
change in the ECT display will indicate the location of
the fault.

Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often

6E–347

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.

Engine Coolant Temperature Sensor

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

6E–348

6VE1 3.5 ENGINE DRIVEABILITY AND EMISSIONS

DTC P1115 – ECT Sensor Circuit Intermittent High Voltage

Step

Action

Value(s)

Yes

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

—

Go to

Step 2

Go to

OBD

System

Check

Is DTC P0118 also set?

—

Go to

DTC

P0118 chart

first

Go to

Step 3

Is DTC P1111 also set?

—

Go to

Step 8

Go to

Step 4

1. Check for a poor sensor ground circuit terminal

connection at the ECT sensor.

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

Was a problem found?

—

Verify repair

Go to

Step 5

1. Check for a poor ECT signal circuit terminal

connection at the ECT sensor.

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

Was a problem found?

—

Verify repair

Go to

Step 6

1. Check the ECT signal circuit between the ECT

sensor connector and the PCM for an intermittent
open.

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

Was a problem found?

—

Verify repair

Go to

Step 7

1. Check the ECT signal circuit between the ECT

sensor connector and the PCM for an intermittent
short to voltage.

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

Was a problem found?

—

Verify repair

Go to

Step 8

1. Check for a poor sensor ground circuit terminal

connection at the PCM.

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

Was a problem found?

—

Verify repair

Go to

Step 9

1. Check for an intermittent open or a faulty splice in

the sensor ground circuit.

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

Was a problem found?

—

Verify repair

Check the

Procedure

Refer to

Diagnostic

Aids

6E–349

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code(DTC)

P1120-TPS 1 Throttle Position Sensor (TPS1) Circuit Fault

D06RY00088

Circuit Description

The throttle position (TP) sensor circuit provides a
voltage signal relative to throttle blade angle.
The throttle blade angle will vary about 8 % at closed
throttle to about 92 % at wide open throttle(WOT).

This code detects a continuous short to ground or
high in either the cicuit or the sensor.

Conditions for setting the DTC

The Ignition is “ON”.

The throttle blade angle is less than 2.5 % or more tnan
97.5 % for 18 failres within 500 test samples (15.6m
sec)

Action Taken When the DTC Sets

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

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 histror DTC P1120 will clear after 40 cosecutive trip
cycle during which the warm up cycles have occurred
without a fault.

DTC P1120 can be cleared using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

Diagnostic Aids

An intermittent may be caused by the following:

Poor connectons.

Mis routed harness.

Rubbed through wire insulation.

Broken wire inside the insulation.

Check for the following conditions:

The MAP sensor shares a 5 Volt reference with the
Fuel Tank Pressure, APS1, APS3 and EGR value.

The MAP sensor shares a ground with the Fuel Tank
Pressure, the ECT sensor, and the Transmission Fluid.

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
TPS 1 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.

Content .. 492 493 494 495 ..