Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 829

6E–45

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Engine Control Module ECM

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 ECM memory.
Diagnostic trouble codes can also be cleared by turning
the ignition “OFF” and disconnecting the battery power
from the ECM for 30 seconds.  Turning off the ignition and
disconnecting the battery power from the ECM will cause
all diagnostic information in the ECM memory to be
cleared.  Therefore, all the diagnostic tests will have to be
re-run.
Since the ECM 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 ECM connections
or the ECM is the cause of a problem, and the ECM is
replaced, but this does not correct the problem, one of the
following may be the reason:

D

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

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 components 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
ECM using internal electronic switches called drivers.
A shorted solenoid, relay coil, or harness will not
damage the ECM but will cause the solenoid or relay to
be inoperative.

Multiple ECM Information Sensor

DTCS Set

Circuit Description

The Engine Control Module ECM monitors various
sensors to determine the engine operating conditions.
The ECM controls fuel delivery, spark advance,
transmission operation, and emission control device
operation based on the sensor inputs.
The ECM provides a sensor ground to all of the sensors.
The ECM 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 (ETC) sensor

D

The intake air temperature (IAT) sensor

The ECM provides the following sensors with a 5-volt
reference and a sensor ground signal:

D

The throttle position (TP) sensor

D

The barometric pressure (BARO) sensor

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

Diagnostic Aids

IMPORTANT:

Be sure to inspect ECM 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

P0108

D

P0113

D

P0118

D

P0123

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 ECM
and the splice will cause one or more of the following
DTCs to be set:

D

P0108

D

P0113

D

P0118

D

P0123

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

P0107

D

P0122

An the in the 5-volt reference circuit A, between the ECM
and the splice will cause one or more of the following
DTCs to be set:

D

P0122

An the in the 5-volt reference circuit B, between the ECM
and the splice will cause one or more of the following
DTCs to be set:

D

P0107

Check for the following conditions:

D

Poor connection at ECM. 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’s 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

IAT

D

ECT

D

TP

D

BARO

6E–46

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Multiple ECM Information Sensor DTCs Set

 

Step

Action

Value(s)

Yes

No

1

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

—

Go to 

Step 2

Go to 

OBD

System

Check

2

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

circuit for the following conditions:

D

A poor connection at the ECM.

D

An open between the ECM 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 ECM or the affected
sensors.

D

An open between the ECM 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

Measure the voltage between the BARO sensor signal
circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value?

0 V

Go to 

Step 7

Go to 

Step 11

7

Measure the voltage between the TP sensor signal
circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value?

0 V

Go to 

Step 8

Go to 

Step 12

8

Measure the voltage between the IAT sensor signal
circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value?

0 V

Go to 

Step 9

Go to 

Step 13

9

Measure the voltage between the ECT sensor signal
circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value?

0 V

Go to 

Step 10

Go to 

Step 14

10

Measure the voltage between the TFT sensor signal
circuit at the ECM harness connector and ground.

Does the voltage measure near the specified value?

0 V

Go to 

Step 15

Go to 

Step 16

11

Locate and repair the short to voltage in the BARO
sensor signal circuit.

Is the action complete?

—

Verify repair

—

12

Locate and repair the short to voltage in the TP sensor
signal circuit.

Is the action complete?

—

Verify repair

—

6E–47

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Multiple ECM Information Sensor DTCs Set

  (Cont'd)

Step

No

Yes

Value(s)

Action

13

Locate and repair the short to voltage in the IAT sensor
signal circuit.

Is the action complete?

—

Verify repair

—

14

Locate and repair the short to voltage in the ECT
sensor signal circuit.

Is the action complete?

—

Verify repair

—

15

Locate and repair the short to voltage in the TFT sensor
signal circuit.

Is the action complete?

—

Verify repair

—

16

Replace the ECM.

Is the action complete?

—

Go to 

OBD

System

Check

—

6E–48

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Tech 2 Data Definitions and Ranges

A/C CLUTCH–Tech 2 Displays ON or OFF–
Indicates whether the ECM 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 ECM 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 ECM commanded value.  In
closed loop, the air/fuel ratio should normally be
displayed around “14.2–14.7.”  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.

BARO kpa — Tech 2 Range 10-105 kpa/0.00-5.00
Volts —
The barometric pressure reading is determined from the
BARO 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.

CMP ACT. COUNTER –Cam Position
ActivityDECEL FUEL MODE—Tech 2 Display
ACTIVE or INACTVE—
“ACTIVE” displayed indicates that the ECM has detected
conditions appropriate to operate in deceleration fuel
mode.  The ECM will command the deceleration fuel
mode when it detects a closed throttle position while the
vehicle is traveling over 20 mph.  While in the decreasing
fuel mode, the ECM will decrease the amount of fuel
delivered by entering open loop and decreasing the
injector pulse width.

DESIRED IDLE — Tech 2 Range 0-3187 RPM —
The idle speed that the ECM is commanding.  The ECM
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 ECM.  The ECM 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 ECM
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 ECM will interpret
the lower voltage as a warm engine.

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

TIME FROM START — 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 ECM from the 58X
reference input.  It should remain close to desired idle
under various engine loads with engine idling.

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

FUEL TRIM CELL —  Tech 2 Range 0-21 —
The fuel trim cell is dependent upon engine speed and
MAF sensor readings.  A plot of RPM vs.  MAF is divided
into 22 cells. Fuel trim cell indicates which cell is currently
active.

FUEL TRIM LEARN
 — Tech 2 Displays NO or YES —
When conditions are appropriate for enabling long term
fuel trim corrections, fuel trim learn will display “YES.”
This indicates that the long term fuel trim is responding to
the short term fuel trim.  If the fuel trim learn displays
“NO,” then long term fuel trim will not respond to changes
in short term fuel trim.

HO2S SEN.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 SEN.Tech 2 Displays READY YES/NO–
Indicates the status of the exhaust oxygen sensor.  The
Tech 2 will indicate that the exhaust oxygen sensor is
ready when the ECM detects a fluctuating HO2S voltage
sufficient to allow closed loop operation.  This will not
occur unless the exhaust oxygen sensor is warmed up.

IAC POSITION — Tech 2 Range 0-255 Counts —
Displays the commanded position of the idle air control
pintle in counts.  A larger number of counts means that
more air is being commanded through the idle air
passage.  Idle air control should respond fairly quickly to
changes in engine load to maintain desired idle RPM.

IAT (INTAKE AIR TEMPERATURE)— Tech 2 Range
–40

°

C to 151

°

C (–40

°

F to 304

°

F) —

The ECM converts the resistance of the intake air
temperature sensor to degrees.  Intake air temperature
(IAT) is used by the ECM to adjust fuel delivery and spark
timing according to incoming air density.

IGNITION VOLTAGE
 — Tech 2 Range 0-25.5 Volts —
This represents the system voltage measured by the
ECM at its ignition feed.