6E2–26
6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
(“Check Engine” lamp). Small leaks in the exhaust
system near the post catalyst oxygen sensor can also
cause the MIL (“Check Engine” lamp) to turn on.
Aftermarket electronics, such as transceiver, stereos,
and anti-theft devices, may radiate EMI into the control
system if they are improperly installed. This may cause a
false sensor reading and turn on the MIL (“Check Engine”
lamp).
Environment
Temporary environmental conditions, such as localized
flooding, will have an effect on the vehicle ignition system.
If the ignition system is rain-soaked, it can temporarily
cause engine misfire and turn on the MIL (“Check Engine”
lamp).
Emissions Control Information Label
The engine compartment “Vehicle Emissions Control
Information Label” contains important emission
specifications and setting procedures. In the upper left
corner is exhaust emission information. There is also an
illustrated emission components and vacuum hose
schematic.
This label is located in the engine compartment of every
vehicle. If the label has been removed it should be
replaced. It can be ordered from Isuzu Dealer ship.
Maitenance Schedule
Refer to the
Maintenance Schedule.
Visual/Physical Engine Compartment
Inspection
Perform a careful visual and physical engine
compartment inspection when performing any diagnostic
procedure or diagnosing the cause of an emission test
failure. This can often lead to repairing a problem without
further steps. Use the following guidelines when
performing a visual/physical inspection:
D
Inspect all vacuum hoses for pinches, cuts,
disconnections, and proper routing.
D
Inspect hoses that are difficult to see behind other
components.
D
Inspect all wires in the engine compartment for proper
connections, burned or chafed spots, pinched wires,
contact with sharp edges or contact with hot exhaust
manifolds or pipes.
Basic Knowledge of Tools Required
NOTE: Lack of basic knowledge of this powertrain when
performing diagnostic procedures could result in an
incorrect diagnosis or damage to powertrain
components. Do not attempt to diagnose a powertrain
problem without this basic knowledge.
A basic understanding of hand tools is necessary to effec-
tively use this section of the Service Manual.
Seral Data Communications
Class II Serial Data Communications
Government regulations require that all vehicle
manufacturers establish a common communication
system. This vehicle utilizes the “Class II”
communication system. Each bit of information can have
one of two lengths: long or short. This allows vehicle
wiring to be reduced by transmitting and receiving
multiple signals over a single wire. The messages carried
on Class II data streams are also prioritized. If two
messages attempt to establish communications on the
data line at the same time, only the message with higher
priority will continue. The device with the lower priority
message must wait. The most significant result of this
regulation is that it provides Tech 2 manufacturers with
the capability to access data from any make or model
vehicle that is sold.
The data displayed on the other Tech 2 will appear the
same, with some exceptions. Some scan tools will only
be able to display certain vehicle parameters as values
that are a coded representation of the true or actual value.
For more information on this system of coding, refer to
Decimal/Binary/Hexadecimal Conversions. On this
vehicle the Tech 2 displays the actual values for vehicle
parameters. It will not be necessary to perform any
conversions from coded values to actual values.
On-Board Diagnostic (OBD)
On-Board Diagnostic Tests
A diagnostic test is a series of steps, the result of which is
a pass or fail reported to the diagnostic executive. When
a diagnostic test reports a pass result, the diagnostic
executive records the following data:
D
The diagnostic test has been completed since the last
ignition cycle.
D
The diagnostic test has passed during the current
ignition cycle.
D
The fault identified by the diagnostic test is not
currently active.
When a diagnostic test reports a fail result, the diagnostic
executive records the following data:
D
The diagnostic test has been completed since the last
ignition cycle.
D
The fault identified by the diagnostic test is currently
active.
D
The fault has been active during this ignition cycle.
D
The operating conditions at the time of the failure.
Remember, a fuel trim DTC may be triggered by a list of
vehicle faults. Make use of all information available (other
DTCs stored, rich or lean condition, etc.) when
diagnosing a fuel trim fault.