Isuzu Trooper (1998-2002 year). Manual - part 612

6E–96

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0198 (Flash DTC 16)

Oil Temp Sensor High Voltage

060RW129

Circuit Description

The engine oil temperature (OT) sensor is a thermistor
mounted in the oil rail. The Engine Control Module ECM
applies a voltage (about 5 volts) through a pull-up resistor
to the ECT signal circuit. When the engine oil is cold, the
sensor (thermistor) resistance is high, therefore the ECM
will measure a high signal voltage. As the engine oil
warms, the sensor resistance becomes lower, and the OT
signal voltage measured at the ECM drops.

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 P0198 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
OT display on the Tech 2 while moving connectors and
wiring harnesses related to the OT sensor. A change
in the OT display will indicate the location of the fault.

If DTC P0198 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
If it is determined that the DTC occurs intermittently.

6E–97

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Verifies that the fault is present.

3. If DTC P0198 can be repeated only by duplicating

the Failure Records conditions, refer to the
“Temperature vs. Resistance Value” table. The
table may be used to test the OT sensor at various
temperatures to evaluate the possibility of a
“shifted” sensor that may be shorted above or below
a certain temperature. If this is the case, replace
the OT sensor. If the OT sensor appears to be OK,
the fault is intermittent; refer to

Diagnostic Aids.

Engine Oil Temperature Sensor

Ohms

Temperature vs. Resistance Values

(approximate)

176

332

2796

4450

DTC P0198 – OT Sensor 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

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

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

–39

(–38

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 “ DTC” info for DTC

P0198.

Does the Tech 2 indicate DTC P0198 failed?

—

Refer to

Test

Description

Refer to

Diagnostic

Aids

1. Disconnect the OT sensor electrical connector.
2. Jumper the OT signal circuit and the sensor ground

circuit together at the OT sensor harness
connector.

3. Observe the “Eng Oil Temp” display on the Tech 2.

Is the “Eng Oil Temp” at the specified value?

140

(284

Go to

Step 6

Go to

Step 5

1. Jumper the OT signal circuit at the OT sensor

harness connector to chassis ground.

2. Observe the “Eng Oil Temp” display on the Tech 2.

Is the “Eng Oil Temp” at the specified value?

140

(284

Go to

Step 7

Go to

Step 8

Check for poor connections at the OT sensor and
replace terminals if necessary.

Did any terminals require replacement?

—

Verify repair

Go to

Step 10

1. Ignition “OFF.”
2. Disconnect the ECM, and check the OT sensor

ground circuit for an open.

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

necessary.

Was the OT sensor ground circuit open?

—

Verify repair

Go to

Step 9

6E–98

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

DTC P0198 – OT Sensor High Voltage

(Cont'd)

Step

Yes

Value(s)

Action

1. Ignition “OFF.”
2. Disconnect the OT, and check the OT signal circuit

for an open.

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

necessary.

Was the OT signal circuit open?

—

Verify repair

Go to

Step 9

Check for a poor sensor ground or OT signal circuit
terminal connection at the ECM 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 ECM (Refer to the Data Programming in
Case of ECM change).

Is the action complete?

—

Verify repair

—

6E–99

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0201 (Flash DTC 51)

Injector # 1 Circuit Fault

060RW134

Circuit Description

The Engine Control Module ECM has four individual
injector driver circuits. Each controls an injector. When a
driver circuit is grounded by the ECM, the injector is
activated. The ECM monitors the current in each driver
circuit. The voltage on each driver is monitored to detect
a fault. If the voltage is not what the ECM expects to
monitor on the circuit, a DTC is set. This DTC is also set if
an injector driver is shorted to voltage or if there is an open
circuit.

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 P0201 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the ECM battery
feed.

Diagnostic Aids

An injector driver circuit that is open or shorted to voltage
will cause a DTC P0201 to set.

Test Description

The number(s) below refer to the step number(s) on the
Diagnostic Chart.

3. This step determines if DTC P0201 is the result of a

hard failure or an intermittent condition.

Injector Test

This test is conducted to make it sure that appropriate
electric signals are being sent to injectors Nos. 1–4.
Tech–2 must be used for this test.

Test Procedure:

Connect Tech–2 to the vehicle DLC.

Set Ignition Switch to the “ON” position.

Select Control Test.

Select Injector Test.

Send instructions to each injector (Switch on),
making sure of injector working noise.

NOTE: If injector working noise (Clink) can hardly be
confirmed, remove the engine head cover noise
insulation.

Refer to Section 6A.

In the injector whose working noise has been
confirmed, its electric circuit can be regarded as
normal.

As for the injector whose working noise has not
been confirmed, its electric circuit or the injector
proper is faulty.

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