Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 773

6E–116

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Fuel System Diagnosis

  (Cont'd)

Step

No

Yes

Value(s)

Action

18

1. Relieve the fuel pressure.  Refer to the 

Fuel

Pressure Relief.

2. Disconnect the fuel return line from the fuel rail.
3. Attach a length of flexible hose to the fuel rail return

outlet passage.

4. Place the open end of the flexible hose into an

approved gasoline container.

5. Run the fuel pump with the Tech 2.
6. Observe the fuel pressure indicated by the fuel

pressure gauge with the fuel pump running.

Is the fuel pressure within the specified limits?

290-376 kPa

(42-55 psi)

Go to 

Step 19

Go to 

Step 20

19

Locate and correct the restriction in the fuel return line.

Is the action complete?

—

Verify repair

—

20

Visually and physically inspect the fuel rail outlet
passages for a restriction.

Was a restriction found?

—

Verify repair

Go to 

Step 11

21

Is the fuel pressure indicated by the fuel pressure
gauge above the specified value?

0 kPa (0 psi)

Go to 

Step 22

Go to 

Step 23

22

1. Command the fuel pump “ON” with the Tech 2.
2. Using suitable pliers which will not damage the fuel

hose, gradually apply pressure with the pliers to
pinch the flexible fuel return hose closed.

CAUTION: Do not let the fuel pressure exceed
the second specified value.

Does the fuel pressure indicated by the fuel pressure
gauge rise above the first specified value?

376 kPa

(55 psi)

414 kPa

(60 psi)

Go to 

Step 11

Go to 

Step 7

23

1. Command the fuel pump “ON” with the Tech 2.
2. Remove the fuel filler cap and listen for the sound of

the fuel pump running.

3. Turn the pump off.

Was the fuel pump running?

—

Go to 

Step 7

Go to 

Fuel

System

Electrical Test

Chart

6E–117

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Exhaust Gas Recirculation (EGR) System Check

D06R200087

Circuit Description

A properly operation exhaust gas recirculation (EGR)
system will directly affect the air/fuel requirements of the
engine.  Since the exhaust gas introduced into the air/fuel
mixture is an inert gas (contains very little or no oxygen),
less fuel is required to maintain a correct air/fuel ratio.
Introducing exhaust gas into the combustion chamber
lowers combustion temperatures and reduces the
formation of oxides of nitrogen (NOx) in the exhaust gas.
Lower combustion temperatures also prevent detonation.
If the EGR pintle were to stay closed, the inert exhaust
gas would be replaced with air and the air/fuel mixture
would be leaner.  The powertrain control module (PCM)
would compensate for the lean condition by adding fuel,
resulting in higher long term fuel trim values.

Diagnostic Aids

The EGR valve chart is a check of the EGR system.  An
EGR pintle constantly in the closed position could cause
detonation and high emissions of NOx.  It could also result
in high long term fuel trim values in the open throttle cell,
but not in the closed throttle cell.  An EGR pintle
constantly in the open position would cause a rough idle.
Also, an EGR mounted incorrectly (rotated 180

°

) could

cause rough idle.  Check for the following items:

D

EGR passages – Check for restricted or blocked EGR
passages.

D

Manifold absolute pressure sensor – A manifold
absolute pressure sensor may shift in calibration
enough to affect fuel delivery.  Refer to 

Manifold

Absolute Pressure Output Check.

6E–118

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Exhaust Gas Recirculation (EGR) System Check

 

Step

Action

Value(s)

Yes

No

1

Check the EGR valve for looseness.

Is the EGR valve Loose?

—

Go to 

Step 2

Go to 

Step 3

2

Tighten the EGR valve.

Is the action complete?

—

Verify repair

—

3

1. Place the transmission selector in Park or Neutral.
2. Start the engine and idle until warm.
3. Using a Tech 2, command EGR “50% ON”.

(Refer to the Miscellaneous Test.)

Does the engine idle rough and lose RPMs?

—

EGR system

working

properly.  No

problem

found.

Go to 

Step 4

4

1. Engine “OFF”.
2. Ignition “ON”.
3. Using a test light to ground, check the EGR harness

between the EGR valve and the ignition feed.

Does the test light illuminate?

—

Go to 

Step 6

Go to 

Step 5

5

Repair the EGR harness ignition feed.

Was the problem corrected?

—

Verify repair

Go to 

Step 6

6

1. Remove the EGR valve.
2. Visually and physically inspect the EGR valve

pintle, valve passages and adapter for excessive
deposits, obstructions or any restrictions.

Does the EGR valve have excessive deposits,
obstructions or any restrictions?

—

Go to 

Step 7

Go to 

Step 8

7

Clean or replace EGR system components as
necessary.

Was the problem corrected?

—

Verify repair

Go to 

Step 8

8

1. Ground the EGR valve metal case to battery (–).
2. Using a Tech 2, command EGR “ON” and observe

the EGR valve pintle for movement.

Does the EGR valve pintle move according to
command?

—

Go to 

Step 9

Go to 

DTC

P1406 chart

9

1. Remove the EGR inlet and outlet pipes from the

intake and exhaust manifolds.

2. Visually and physically inspect manifold EGR ports

and EGR inlet and outlet pipes for blockage or
restriction caused by excessive deposits or other
damage.

Do the manifold EGR ports or inlet and outlet pipes
have excessive deposits, obstructions, or any
restrictions?

—

Go to 

Step 10

EGR system

working

properly.  No

problem

found.

10

Clean or replace EGR system components as
necessary.

Is the action complete?

—

Verify repair

—

6E–119

TROOPER 6VE1 3.5L 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.