General Service Information; Obd Ii Serviceability Issues; Emissions Control Information Label - Isuzu 1999 RODEO Workshop Manual

6E1–28
RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
GENERAL SERVICE
INFORMATION

OBD II Serviceability Issues

With the introduction of OBD II diagnostics across the
entire passenger car and light–duty truck market in 1996,
illumination of the MIL ("Check Engine" lamp) due to a
non–vehicle fault could lead to misdiagnosis of the
vehicle, increased warranty expense and customer
dissatisfaction. The following list of non–vehicle faults
does not include every possible fault and may not apply
equally to all product lines.
Fuel Quality
Fuel quality is not a new issue for the automotive industry,
but its potential for turning on the MIL ("Check Engine"
lamp) with OBD II systems is new.
Fuel additives such as "dry gas" and "octane enhancers"
may affect the performance of the fuel. If this results in an
incomplete combustion or a partial burn, it will show up as
a Misfire DTC P0300. The Reid Vapor Pressure of the fuel
can also create problems in the fuel system, especially
during the spring and fall months when severe ambient
temperature swings occur. A high Reid Vapor Pressure
could show up as a Fuel Trim DTC due to excessive
canister loading. High vapor pressures generated in the
fuel tank can also affect the Evaporative Emission
diagnostic as well.
Using fuel with the wrong octane rating for vehicle may
cause driveability problems. Many of the major fuel
companies advertise that using "premium" gasoline will
improve the performance of vehicle. Most premium fuels
use alcohol to increase the octane rating of the fuel.
Although alcohol–enhanced fuels may raise the octane
rating, the fuel's ability to turn into vapor in cold
temperatures deteriorates. This may affect the starting
ability and cold driveability of the engine.
Low fuel levels can lead to fuel starvation, lean engine
operation, and eventually engine misfire.
Non–OEM Parts
All of the OBD II diagnostics have been calibrated to run
with OEM parts. Something
high–performance exhaust system that affects exhaust
system back pressure could potentially interfere with the
operation of the EGR valve and thereby turn on the MIL
("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).
as simple as a
Refueling
A new OBD II diagnostic was introduced in 1996 on some
vehicles. This diagnostic checks the integrity of the entire
evaporative emission system. If the vehicle is restarted
after refueling and the fuel cap is not secured correctly,
the on–board diagnostic system will sense this as a
system faultand turn on the MIL ("Check Engine" lamp)
with a DTC P0440.
Vehicle Marshaling
The transportation of new vehicles from the assembly
plant to the dealership can involve as many as 60 key
cycles within 2 to 3 miles of driving. This type of operation
contributes to the fuel fouling of the spark plugs and will
turn on the MIL ("Check Engine" lamp) with a P0300
Misfire DTC.
Poor Vehicle Maintenance
The sensitivity of OBD II diagnostics will cause the MIL
("Check Engine" lamp) to turn ON if the vehicle is not
maintained properly. Restricted air filters, fuel filters, and
crankcase deposits due to lack of oil changes or improper
oil viscosity can trigger actual vehicle faults that were not
previously monitored prior to OBD II. Poor vehicle
maintenance can't be classified as a "non–vehicle fault",
but with the sensitivity of OBD II diagnostics, vehicle
maintenance schedules must be more closely followed.
Severe Vibration
The Misfire diagnostic measures small changes in the
rotational speed of the crankshaft. Severe driveline
vibrations in the vehicle, such as caused by an excessive
amount of mud on the wheels, can have the same effect
on crankshaft speed as misfire and therefore may set a
Misfire DTC P0300.
Related System Faults
Many of the OBD II system diagnostics will not run if the
PCM detects a fault on a related system or component.
One example would be that if the PCM detected a Misfire
fault, the diagnostics on the catalytic converter would be
suspended until the Misfire fault was repaired. If the
Misfire fault was severe enough, the catalytic converter
could be damaged due to overheating and would never
set a Catalyst DTC until the Misfire fault was repaired and
the Catalyst diagnostic was allowed to run to completion.
If this happens, the customer may have to make two trips
to the dealership in order to repair the vehicle.

Emissions Control Information Label

The engine compartment "Vehicle Emissions Control
Information Label" contains
specifications and setting procedures. In the upper left
corner is exhaust emission information. This identifies the
emission standard (Federal, California, or Canada) of the
engine, the displacement of the engine in liters, the class
of the vehicle, and the type of fuel metering system. 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.
important emission