Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 763

6E–76

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
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 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

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

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:

D

P0453

D

P0106, P0107, P1107

D

P0401, P1404, P0405

D

P1120, P1515, P1221, P1516, P1635

6E–77

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

D

P1275, P1639, P1271, P1273

D

P1285, P1272, P1273

D

P0336, P0337

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 (Fuel Tank Pressure) Sensor

D

MAP Sensor

D

EGR

D

TPS1/TPS2

D

APS1/APS2/APS3

D

CKP

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

—

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)

Is the resistance near the specified value?

—

Go to 

Step 9

Go to 

Step 8

6E–78

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Multiple PCM Information Sensor DTCs Set

  (Cont'd)

Step

No

Yes

Value(s)

Action

8

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

Is the action complete?

—

Verify repair

—

9

1.  Disconnect the MAP, Vapor pressure sensor and

EGR connector.

2.  Ignition “ON”.
3.  Measure the resistance of the blow areas:

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

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

1.  Disconnect the CKP sensor connector.
2.  Ignition “ON”.
3.  Measure the voltage of the blow areas:

D

 CKP sensor GND circuit and shield circuit.

Does the voltage resistance near the specified value?

—

Go to 

Step 13

Go to 

Step 12

12

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

Is the action complete?

—

Verify repair

—

13

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

—

Go to

applicable
DTC table

Go to 

Step 14

14

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 PROGRAMMED SOFTWARE to the
replacement PCM.

Is the action complete?

—

Go to 

OBD

System

Check

—

6E–79

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Exhaust Gas Recirculation (EGR)

Diagnosis

An EGR flow check diagnosis of the linear EGR system is
covered by DTC P0401. Pintle position error diagnosis is
covered by DTC P0402, P0404, P1404, P0405, P0406. If
EGR diagnostic trouble codes P0401 and/or P0402,
P0404, P1404, P0405, P0406 are encountered, refer to
the DTC charts.

Engine Tech 2 Data Definitions and

Ranges

A/C CLUTCH – Tech 2 Displays ON or OFF –
Indicates whether the PCM has commanded the A/C
clutch ON.  Used in A/C system diagnostic.

A/C REQUEST — Tech 2 Displays YES or NO —
Indicates the state of the A/C request input circuit from the
HVAC controls.  The PCM uses the A/C request signal to
determine whether A/C compressor operation is being
requested.

AIR/FUEL RATIO — Tech 2 Range 0.0-25.5 —
Air/fuel ratio indicates the PCM commanded value.  In
closed loop, the air/fuel ratio should normally be
displayed around “14.6-14.7”.  A lower air/fuel ratio
indicates a richer commanded mixture, which may be
seen during power enrichment or TWC protection modes.
A higher air/fuel ratio indicates a leaner commanded
mixture.  This can be seen during deceleration fuel mode.

AP1 —Tech 2 Range 0%-100% —
AP (accelerator pedal) angle is computed by the PCM
from the AP sensor voltage. AP angle should display
“11-15%” at idle and “85-89%” at wide open throttle.

AP2 —Tech 2 Range 0%-100% —
AP (accelerator pedal) angle is computed by the PCM
from the AP sensor voltage. AP angle should display
“85-89%” at idle and “11-15%” at wide open throttle.

AP3 —Tech 2 Range 0%-100% —
AP (accelerator pedal) angle is computed by the PCM
from the AP sensor voltage. AP angle should display
“85-89%” at idle and “32-36%” at wide open throttle.

BAROMETRIC PRESSURE — Tech 2 Range 10-105
kPa/0.00-5.00 Volts —
The barometric pressure reading is determined from the
MAP sensor signal monitored during key up and wide
open throttle (WOT) conditions.  The barometric pressure
is used to compensate for altitude differences and is
normally displayed around “61-104” depending on
altitude and barometric pressure.

CHECK TRANS LAMP — AUTO TRANSMISSION —
Indicates the need to check for a DTC with the Tech 2
when the lamp is flashing 0.2 seconds ON and 0.2
seconds OFF.

DESIRED EGR POS. — Tech 2 Range 0%-100% —
Represents the EGR pintle position that the PCM is
commanding.

DESIRED IDLE — Tech 2 Range 0-3187 RPM —
The idle speed that the PCM is commanding.  The PCM
will compensate for various engine loads based on engine
coolant temperature,  to keep the engine at the desired
speed.

ECT — (Engine Coolant Temperature) Tech 2
Range –40

°

C to 151

°

C (–40

°

F to 304

°

F) —

The engine coolant temperature (ECT) is mounted in the
coolant stream and sends engine temperature
information to the PCM.  The PCM applies 5 volts to the
ECT sensor circuit.  The sensor is a thermistor which
changes internal resistance as temperature changes.
When the sensor is cold (high resistance), the PCM
monitors a high signal voltage and interprets that as a cold
engine.  As the sensor warms (decreasing resistance),
the voltage signal will decrease and the PCM will interpret
the lower voltage as a warm engine.

EGR DUTY CYCLE — Tech 2 Range 0%-100% —
Represents the EGR valve driver PWM signal from the
PCM.  A duty cycle of 0% indicates that no EGR flow is
being commanded; a 100% duty cycle indicates
maximum EGR flow commanded.

EGR FEEDBACK — Tech 2 Range 0.00-5.00 Volts —
Indicates the EGR pintle position sensor signal voltage
being monitored by the PCM.  A low voltage indicates a
fully extended pintle (closed valve); a voltage near 5 volts
indicates a retracted pintle (open valve).

ENGINE LOAD — Tech 2 Range 0%-100% —
Engine load is calculated by the PCM from engine speed
and MAF sensor readings.  Engine load should increase
with an increase in RPM or air flow.

ENGINE RUN TIME — Tech 2 Range
00:00:00-99:99:99 Hrs:Min:Sec —
Indicates the time elapsed since the engine was started.
If the engine is stopped, engine run time will be reset to
00:00:00.

ENGINE SPEED — Range 0-9999 RPM —
Engine speed is computed by the PCM from the 58X
reference input.  It should remain close to desired idle
under various engine loads with engine idling.

EVAP PURGE PWM — Tech 2 Range 0%-100% —
Represents the PCM commanded PWM duty cycle of the
EVAP purge solenoid valve.  “0%” displayed indicates no
purge; “100%” displayed indicates full purge.

FUEL PUMP — Tech 2 Displays ON or OFF —
Indicates the PCM commanded state of the fuel pump
relay driver circuit.

HO2S BANK 1, SEN. 1
 — Tech 2 Range 0-1132 mV —
 Represents the fuel control exhaust oxygen sensor
output voltage.  Should fluctuate constantly within a range
between 10 mV (lean exhaust) and 1000 mV (rich
exhaust) while operating in closed loop.

HO2S BANK 1, SEN. 2
 — Tech 2 Range 0-1000mV —
 Monitors the exhaust oxygen sensor output voltage. The
PCM monitors the operating efficiency of catalytic
converter  by comparing the output voltages of sensor 1
and sensor 2 in this bank.  If the catalytic converter is
operating efficiently, the output voltage of sensor 1 will
give a greater fluctuation than that of sensor  2.  If the
PCM detects an abnormal level of voltage fluctuation
from sensor 2, a DTC P0420 will be set, indicating that the
catalytic converter for this bank is no longer operating
efficiently.