Isuzu Trooper (2000 year). Manual — part 237

6E–77

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Powertrain Control Module (PCM)

Diagnosis

To read and clear diagnostic trouble codes, use a Tech 2.
IMPORTANT:

Use of a Tech 2 is recommended to clear

diagnostic trouble codes from the PCM memory.
Diagnostic trouble codes can also be cleared by turning
the ignition “OFF” and disconnecting the battery power
from the PCM for 30 seconds. Turning off the ignition and
disconnecting the battery power from the PCM will cause
all diagnostic information in the PCM memory to be
cleared. Therefore, all the diagnostic tests will have to be
re-run.
Since the PCM can have a failure which may affect only
one circuit, following the diagnostic procedures in this
section will determine which circuit has a problem and
where it is.
If a diagnostic chart indicates that the PCM connections
or the PCM is the cause of a problem, and the PCM is
replaced, but this does not correct the problem, one of the
following may be the reason:

D

There is a problem with the PCM terminal
connections. The terminals may have to be removed
from the connector in order to check them properly.

D

EEPROM program is not correct for the application.
Incorrect components or reprogramming the PCM
with the wrong EEPROM program may cause a
malfunction and may or may not set a DTC.

D

The problem is intermittent. This means that the
problem is not present at the time the system is being
checked. In this case, refer to the

Symptoms portion

of the manual and make a careful physical inspection
of all component and wiring associated with the
affected system.

D

There is a shorted solenoid, relay coil, or harness.
Solenoids and relays are turned “ON” and “OFF” by
the PCM using internal electronic switches called
drivers. A shorted solenoid, relay coil, or harness will
not damage the PCM but will cause the solenoid or
relay to be inoperative.

Multiple PCM Information Sensor

DTCs Set

Circuit Description

The powertrain control module (PCM) monitors various
sensors to determine the engine operating conditions.
The PCM controls fuel delivery, spark advance,
transmission operation, and emission control device
operation based on the sensor inputs.
The PCM provides a sensor ground to all of the sensors.
The PCM applies 5 volts through a pull–up resistor, and
determines the status of the following sensors by
monitoring the voltage present between the 5–volt supply
and the resistor:

D

The engine coolant temperature (ECT) sensor

D

The intake air temperature (IAT) sensor

D

The transmission fluid temperature (TFT) sensor

The PCM provides the following sensors with a 5–volt
reference and a sensor ground signal:

1

D

The exhaust gas recirculating (EGR) pintle position

D

sensor

D

The manifold absolute pressure (MAP) sensor

D

The throttle position (TP) sensor 1

D

The acceleration position (AP) sensor 1

D

The acceleration position (AP) sensor 3

D

The Vapor Pressure Sensor

2

D

The Crank position (CKP) sensor

D

The Camshaft Position (CMP) Sensor

D

The throttle position (TP) sensor 2

D

The acceleration position (AP) sensor 2

The PCM monitors the separate feedback signals from
these sensors in order to determine their operating
status.

Diagnostic Aids

IMPORTANT:

Be sure to inspect PCM and engine

grounds for being secure and clean.
A short to voltage in one of the sensor input circuits may
cause one or more of the following DTCs to be set:

D

P0425

D

P0108, P1106

D

P0406

D

P1120, P1515, P1221, P1516, P1635

D

P1275, P1639, P1271, P1273

D

P1285, P1272, P1273

D

P0336, P0337

D

P0341, P0342

D

P1220, P1515, P1221, P1515, P1516

D

P1280, P1271, P1272

IMPORTANT:

If a sensor input circuit has been shorted

to voltage, ensure that the sensor is not damaged. A
damaged sensor will continue to indicate a high or low
voltage after the affected circuit has been repaired. If the
sensor has been damaged, replace it.
An open in the sensor ground circuit between the PCM
and the splice will cause one or more of the following
DTCs to be set:

D

P0425

D

P0108,P1106

D

P0406

D

P1120, P1515, P1221, P1516, P1635

D

P1275, P1639, P1271, P1273

D

P1285, P1272, P1273

D

P0336, P0337

D

P0341, P0342

D

P1220, P1515, P1221, P1515, P1516

D

P1280, P1271, P1272

A short to ground in the 5–volt reference A or B circuit will
cause one or more of the following DTCs to be set:

6E–78

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

D

P0453

D

P0106, P0107, P1107

D

P0401, P1404, P0405

D

P1120, P1515, P1221, P1516, P1635

D

P1275, P1639, P1271, P1273

D

P1285, P1646, P1272, P1273

D

P0336, P0337

D

P0341, P0342

D

P1220, P1515, P1221, P1515, P1516

D

P1280, P1271, P1272

Check for the following conditions:

D

Poor connection at PCM. Inspect the harness
connectors for backed–out terminals, improper
mating, broken locks, improperly formed or damage
terminals, and a poor terminal–to–wire connection.

D

Damaged harness. Inspect the wiring harness for
damage. If the harness is not damaged, observe an
affected sensor fs displayed value on the Tech 2 with
the ignition “ON” and the engine “OFF” while you
move the connectors and the wiring harnesses
related to the following sensors:

D

Vapor Pressure Sensor

D

MAP Sensor

D

EGR

D

TPS1/TPS2

D

APS1/APS2/APS3

D

CKP/CMP

6E–79

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Multiple PCM Information Sensor DTCs Set

Step

Action

Value(s)

Yes

No

1

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

—

Go to

Step 2

Go to

OBD

System

Check

2

1. Turn the ignition “OFF,” disconnect the PCM.
2. Turn the ignition “ON,” check the 5 volt reference 1

and 2 circuit for the following conditions:

D

A poor connection at the PCM.

D

An open between the PCM connector and the
splice.

D

A short to ground.

D

A short to voltage.

Is there an open or short?

—

Go to

Step 3

Go to

Step 4

3

Repair the open or short.

Is the action complete?

—

Verify repair

—

4

Check the sensor ground circuit for the following
conditions:

D

A poor connection at the PCM or the affected
sensors.

D

An open between the PCM connector and the
affected sensors.

Is there an open or a poor connection?

—

Go to

Step 5

Go to

Step 6

5

Repair the open or the poor connection.

Is the action complete?

—

Verify repair

—

6

Following below the DTCs stored:
P1635, P1639, P1646

—

Go to

applicable
DTC table

Go to

Step 7

7

Measure the resistance below the items:

D

Between EGR sensor supply circuit and Vapor
Pressure Sensor supply circuit.

D

Between MAP sensor supply circuit and Vapor
Pressure Sensor supply circuit.

D

Between Vapor Pressure Sensor supply circuit
and PCM harness connector. (5Volt supply
circuit)

Does the resistance measure near the specified value?

—

Go to

Step 9

Go to

Step 8

8

Locate and repair the open circuit in the MAP or EGR or
Vapor Pressure sensor suppy circuit.

Is the action complete?

—

Verify repair

—

9

1. Disconnect the MAP , Vapor pressure sensor and

EGR connecter.

2. Ignition “ON.”
3. Measure the resistance below the items:

D

MAP sensor GND circuit.

D

EGR GND circuit.

D

Vapor pressure sensor GND circuit.

Does the voltage resistance near the specified value?

—

Go to

Step 11

Go to

Step 10

6E–80

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Multiple PCM Information Sensor DTCs Set

(Cont'd)

Step

No

Yes

Value(s)

Action

10

Locate and repair the short circuit in the MAP or EGR or
Vapor Pressure sensor signal or GND circuit.

Is the action complete?

—

Verify repair

—

11

Measure the resistance below the items:

D

Between CKP sensor supply circuit and CMP
Sensor supply circuit.

D

Between CKP Sensor supply circuit and PCM
harness connector. (5Volt supply circuit)

Does the voltage resistance near the specified value?

—

Go to

Step 13

Go to

Step 12

12

Locate and repair the open circuit in the CKP or CMP
sensor supply circuit.

Is the action complete?

—

Verify repair

—

13

1. Disconnect the CKP and CMP sensor connector.
2. Ignition “ON.”
3. Measure the voltage below the items:

D

CKP sensor GND circuit and shield circuit.

D

CMP sensor GND circuit and shield circuit.

Does the voltage resistance near the specified value?

—

Go to

Step 15

Go to

Step 14

14

Locate and repair the short circuit in the CKP or CMP
sensor signal or GND circuit.

Is the action complete?

—

Verify repair

—

15

Are more of the following items for DTCs stored? EGR,
Vapor Pressure Sensor, MAP, CKP, CMP, TPS, APS

—

Go to

applicable
DTC table

Go to

Step 16

16

Replace the PCM.

The replacement PCM must be programmed.

Refer to

ON-Vehicle Service in Power 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 PROGRMMED SOFTWARE to the
replacement PCM.

Is the action complete?

—

Go to

OBD

System

Check

—