Isuzu Trooper (1998-2002 year). Manual - part 437

6E–118

6VE1 3.5 ENGINE DRIVEABILITY AND EMISSIONS

Manifold Absolute Pressure (MAP) Output Check

D06R200048

Circuit Description

The manifold absolute pressure (MAP) sensor measures
the changes in the intake MAP which result from engine
load (intake manifold vacuum) and engine speed
changes; and converts these into a voltage output.  The
powertrain control module (PCM) sends a 5-volt
reference voltage to the MAP sensor.  As the MAP
changes, the output voltage of the sensor also changes.
By monitoring the sensor output voltage, the PCM knows
the MAP.  A lower pressure (low voltage) output voltage
will be about 1-2 volts at idle.  Higher pressure (high
voltage) output voltage will be about 4-4.8 volts at wide
open throttle.  The MAP sensor is also used, under certain
conditions, to measure barometric pressure, allowing the
PCM to make adjustments for different altitudes.  The
PCM uses the MAP sensor to diagnose proper operation
of the EGR system, in addition to other functions.

Test Description

IMPORTANT:

Be sure to used the same diagnostic test

equipment for all measurements.
The number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Applying 34 kPa (10 inch Hg) vacuum to the MAP

sensor should cause the voltage to be 1.5-2.1 volts
less than the voltage at step 1.  Upon applying
vacuum to the sensor, the change in voltage should
be instantaneous.  A slow voltage change indicates
a faulty sensor.

3. Check the vacuum hose to the sensor for leaking or

restriction,  Be sure that no other vacuum devices
are connected to the MAP hose.

IMPORTANT:

Make sure the electrical connector

remains securely fastened.

4. Disconnect the sensor from the bracket.  Twist the

sensor with your hand to check for an intermittent
connection.  Output changes greater than 0.10 volt
indicate a bad sensor.

6E–119

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Manifold Absolute Pressure (MAP) Output Check

 

Step

Action

Value(s)

Yes

No

1

1. Turn the ignition “OFF” and leave it “OFF” for 15

seconds.

2. Ignition “ON”.   Don’t crank engine.
3. The Tech 2 should indicate a manifold absolute

pressure (MAP) sensor voltage.

4. Compare this scan reading to scan reading of a

known good vehicle obtained using the exact same
procedure as in Steps 1-4.

Is the voltage reading the same +/–0.40 volt?

—

Go to 

Step 2

Go to 

Step 5

2

1. Disconnect the vacuum hose at the MAP sensor

and plug the hose.

2. Connect a hand vacuum pump to the MAP sensor.
3. Start the engine.
4. Apply 34 kPa (10 in.Hg) of vacuum and note the

voltage change.

Is the voltage change 1.5-2.1 volts less than Step 1?

—

Go to 

Step 3

Go to 

Step 4

3

Check the sensor cover for leakage or restriction.

Does the hose supply vacuum to the MAP sensor only?

—

Go to 

Step 5

Go to 

Step 4

4

Repair the hose blockage.

Is the action complete?

—

Verify repair

—

5

Check the sensor connection.

Is the sensor connection good?

—

Go to 

Step 6

Go to 

Step 7

6

Refer to 

On-Vehicle Service, MAP Sensor.

Is the action complete?

—

Verify repair

—

7

Repair the poor connection.

Is the action complete?

—

Verify repair

—

6E–120

6VE1 3.5 ENGINE DRIVEABILITY AND EMISSIONS

Evaporative (EVAP) Emissions Canister Purge Valve Check

D06R200089

Circuit Description

Canister purge is controlled by a solenoid valve that
allows manifold vacuum to purge the canister.  The
powertrain control module (PCM) supplies a ground to
energize the solenoid valve (purge “ON”).  The EVAP
purge solenoid control is turned “ON” and “OFF” several
times a second.  The duty cycle (pulse width or “ON” time)
is determined by engine operating conditions including
load, throttle position, coolant temperature and ambient
temperature.  The duty cycle is calculated by the PCM
and the purge solenoid is enabled when the appropriate
conditions have been met:

D

The engine run time after start is more than 60
seconds.

D

The engine coolant temperature is above 30

°

C

(86

°

F).

D

The fuel control system is operating in the closed-loop
mode.

Diagnostic Aids

D

Make a visual check of vacuum hoses.

D

Check the throttle body for cracks.

D

Check the malfunction indicator lamp for a possible
mechanical problem.

Test Description

The number(s) below refer to the step number(s) on the
Diagnostic Chart.
1. Check to see if the solenoid is open or closed.  The

solenoid is normally de-energized in this step, so it
should be closed.

2. This step checks to determine if the solenoid was

open due to an electrical circuit problem or a
defective solenoid.

3. This should normally energize the solenoid, opening

the valve and allowing the vacuum to drop (purge
“ON”).

6E–121

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Evaporative (EVAP) Emissions Canister Purge Valve Check

 

Step

Action

Value(s)

Yes

No

1

1. Ignition “OFF”.
2. Ignition “ON”, engine “OFF”.
3. At the throttle body, disconnect the hose that goes

to the purge solenoid.

4. Using a hand vacuum pump with an attached

vacuum gauge J 23738-A, apply vacuum (10 in. Hg
or 34 kPa) to the solenoid.

Does the solenoid hold the vacuum?

—

Go to 

Step 3

Go to 

Step 2

2

1. Disconnect the solenoid electrical connector.
2. As in Step 1, apply vacuum (10 in. Hg or 34 kPa) to

the solenoid.

Does the solenoid hold the vacuum?

—

Go to 

Step 4

Go to 

Step 7

3

1. At the throttle body, put a cap over the vacuum port

where the hose was disconnected for testing.  This
is to prevent a vacuum leak when the engine is
started.

2. Ignition “OFF”.
3. Install the Tech 2.
4. Apply vacuum to the purge solenoid with the hand

vacuum pump.

5. Start the engine, run at 2500 RPM.
6. Using the Tech 2, select Powertrain, 3.5–V6 6VE1,

F3: Misc.  Tests, F2: EVAP Purge, F0: EVAP Purge.

(Refer to the Misellaneous Test.)

7. Turn the purge solenoid “ON”.

Did the vacuum drop when the purge was turned on?

—

Go to 

Step 8

Go to 

Step 9

4

Check for a short to ground in the S7 Pin wire.

Is there a short?

—

Go to 

Step 5

Go to 

Step 6

5

Repair the short to ground.

Is the action complete?

—

Verify repair

—

6

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed.  Refer to 

On-Vehicle Servicein

Powertrain 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?

—

Verify repair

—

7

Replace the faulty purge solenoid.  Refer to 

On-Vehicle

Service, EVAP Canister Purge Solenoid.

Is the action complete?

—

Verify repair

—