Isuzu engine C22NE / 22LE / 20LE. Service manual — part 53
DRIVEABILITY AND EMISSIONS 6E1-41
Engine Component Locator Table
Number
Name
Location
1
Engine Coolant Temperature (ECT) Sensor
Front of engine, next to the thermostat housing
2
Heated Oxygen Sensor (HO2S)
On the exhaust pipe, left side of engine,
immediately behind the exhaust manifold
3
Air Cleaner
Left front the engine bay
4
Intake Air Temperature (IAT) Sensor
On the intake air duct near the air cleaner
5
Positive Crankcase Ventilation (PCV) Port
On the right front corner of the valve cover
6
Fuel Pressure Regulator
On the rear end of the fuel rail
7
Throttle Body
Between the intake air duct and the intake
manifold
8
Fuse/Relay Box
Along the inside of the right fender
9
Throttle Position (TP) Sensor
On the front of the throttle body
10
Idle Air Control (IAC) Valve
Under the TP sensor
11
EVAP Canister Purge Control Solenoid
On the intake manifold
12
Ignition Coil
Above the starter motor
13
Manifold Absolute Pressure (MAP) Sensor
Bolted to the front edge of the intake
manifold, under the fuel rail
*14
EVAP Canister
On the left side Tire house
*15
Check and Relief valve
On the canister hold brace
* If applicable
Undercarriage Component Locator Table
Name
Location
Fuel Pump Assembly
Installed in the top of the fuel tank
EVAP Purge Control Solenoid Valve
At the right rear of the engine
Vehicle Speed Sensor (VSS)
Protrudes from the right side of the transmission
housing, rear the output shaft
Crankshaft Position (CKP) Sensor
Lower left hand front of engine, behind power steering
pump bracket
6E1-42 DRIVEABILITY AND EMISSIONS
UNDERHOOD (U/H) FUSE AND RELAY PANEL
INSTRUMENT PANEL (I/P) FUSE BLOCK
DRIVEABILITY AND EMISSIONS 6E1-43
DIAGNOSIS
STRATEGY-BASED
DIAGNOSTICS
STRATEGY-BASED DIAGNOSTICS
The strategy-based diagnostic is a uniform approach
to repair all Electrical/Electronic (E/E) systems. The
diagnostic flow can always be used to resolve an E/E
system problem and is a starting point when repairs
are necessary. The following steps will instruct the
technician how to proceed with a diagnosis:
1. Verify the customer complaint.
• To verify the customer complaint, the technician
should know the normal operation of the system.
2. Perform preliminary checks.
• Conduct a thorough visual inspection.
• Review the service history.
• Detect unusual sounds or odors.
• Gather diagnostic trouble code information to
achieve an effective repair.
3. Check bulletins and other service information.
• This includes videos, newsletters, etc.
4. Refer to service info (manual) system check(s).
• “System checks” contain information on a
system that may not be supported by one or
more DTCs. System checks verify proper
operation of the system. This will lead the
technician in an organized approach to
diagnostics.
5. Refer to service diagnostics.
DTC STORED
Follow the designated DTC chart exactly to make an
effective repair.
NO DTC
Select the symptom from the symptom tables. Follow
the diagnostic paths or suggestions to complete the
repair. You may refer to the applicable
component/system check in the system checks.
NO MATCHING SYMPTOM
1. Analyze the complaint.
2. Develop a plat for diagnostics.
3. Utilize the wiring diagrams and the theory of
operation.
Call technical assistance for similar cases where
repair history may be available. Combine technician
knowledge with efficient use of the available service
information.
INTERMITTENTS
Conditions that are not always present are called
intermittents. To resolve intermittents, perform the
following steps:
1. Observe DTCs and DTC modes
2. Evaluate the symptoms and the conditions
described by the customer.
3. Use a check sheet or other method to identify the
circuit or electrical system component.
4. Follow the suggestions for intermittent diagnosis
found in the service documentation.
Most Scan Tools, such as the Tech 2 and the 5-8840-
2392-0, have data-capturing capabilities that can
assist in detecting intermittents.
NO TROUBLE FOUND
This condition exists when the vehicle is found to
operate normally. The condition described by the
customer may be normal. Verify the customer
complaint against another vehicle that is operating
normally. The condition may be intermittent. Verify the
complaint under the conditions described by the
customer before releasing the vehicle.
1. Re-examine the complaint.
When the complaint cannot be successfully found
or isolated, a re-evaluation is necessary. The
complaint should be re-verified and could be
intermittent as defined in Intermittents, or could be
normal.
2. Repair and verify.
After isolating the cause, the repairs should be
made. Validate for proper operation and verify that
the symptom has been corrected. This may involve
road testing or other methods to verify that the
complaint has been resolved under the following
conditions:
• Conditions noted by the customer.
• If a DTC was diagnosed, verify a repair by
duplicating conditions present when the DTC
was set as noted in the customer complaint.
6E1-44 DRIVEABILITY AND EMISSIONS
VERIFYING VEHICLE REPAIR
Verification of the vehicle repair will be more
comprehensive for vehicles with OBD system
diagnostics. Following a repair, the technician should
perform the following steps:
Important: Follow the steps below when you verify
repairs on OBD systems. Failure to follow these steps
could result in unnecessary repairs.
1. Review and record the customer complaint for the
DTC which has been diagnosed.
2. Clear the DTC(s).
3. Operate the vehicle within conditions noted in the
customer complaint.
4. Monitor the DTC status information for the specific
DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.
GENERAL SERVICE
INFORMATION
OBD SERVICEABILITY ISSUES
Fuel Quality
Fuel quality is not a new issue for the automotive
industry. The Reed 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 Reed
Vapor Pressure could show up as a rich 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 your
vehicle may cause driveability problems. Many of the
major fuel companies advertise that using “premium”
gasoline will improve the performance of your 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 diagnostics have been calibrated to run
with OEM parts. Small leaks in the exhaust system
near the heated oxygen sensor can also cause the
MIL (“Check Engine“ lamp) to turn on.
Aftermarket electronics, such as cellular phones,
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).
Poor Vehicle Maintenance
The sensitivity of OBD 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.
Poor vehicle maintenance can not be classified as a
“non-vehicle fault” , but with the sensitivity of OBD
diagnostics, vehicle maintenance schedules must be
more closely followed.
Related System Faults
Many of the OBD system diagnostics will not run if the
ECM detects a fault on a related system or
component. One example would be that if the ECM
detected a Evap. Purge Solenoid fault, The diagnosis
on the Oxygen Sensor (If applicable) would be
suspended until the Evap. Purge Solenoid repaired. If
this happened, the customer may have to make two
trips to the dealership in order to repair the vehicle.
MAINTENANCE 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/thysical
inspection:
• Inspect all vacuum hoses for punches, cuts,
disconnects, and correct routing.
• Inspect hoses that are difficult to see behind other
components.
• 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.
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