Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual — part 1417
6E2–119
RODEO 6VD1 3.2L 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
6E2–120
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
Exhaust Gas Recirculation (EGR) System Check
060R200050
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.
6E2–121
RODEO 6VD1 3.2L 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
—
6E2–122
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
Manifold Absolute Pressure (MAP) Output Check
060R200051
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.
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