Symptom Diagnosis - Isuzu 1999 RODEO Workshop Manual

6E2–418
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

Symptom Diagnosis

Preliminary Checks
Before using this section, perform the "On–Board
Diagnostic (OBD) System Check" and verify all of the
following items:
f The
powertrain control
malfunction indicator lamp (MIL) (Check Engine
lamp) are operating correctly.
f There are no DTC(s) stored.
f Tech 2 data is within normal operating range. Refer to
Typical Scan Data Values .
f Verify the customer complaint and locate the correct
symptom in the table of contents.
procedure included in the symptom chart.
Visual/Physical Check
Several of the symptom procedures call for a careful
visual/physical check. This can lead to correcting a
problem without further checks and can save valuable
time.
This check should include the following items:
f PCM grounds for cleanliness, tightness and proper
location.
f Vacuum hoses for splits, kinks, and proper
connections, as shown on the "Vehicle Emission
Control Information" label. Check thoroughly for any
type of leak or restriction.
f Air intake ducts for collapsed or damaged areas.
f Air leaks at throttle body mounting area, mass air flow
(MAF) sensor and intake manifold sealing surfaces.
f Ignition components for cracking, hardness, and
carbon tracking.
f Wiring for proper connections, pinches and cuts.
Intermittents
IMPORTANT: An intermittent problem may or may not
turn on the malfunction indicator lamp (MIL) or store a
DTC. DO NOT use the Diagnostic Trouble Code (DTC)
charts for intermittent problems.
present to locate the problem.
Most intermittent problems are caused by faulty electrical
connections or wiring. Perform a careful visual/physical
check for the following conditions:
f Poor mating of the connector halves or a terminal not
fully seated in the connector (backed out).
f Improperly formed or damaged terminal.
f All connector terminals in the problem circuit should
be carefully checked for proper contact tension.
f Poor terminal–to–wire connection.
removing the terminal from the connector body to
check.
Road test the vehicle with a J 39200 Digital Multimeter
connected to a suspected circuit. An abnormal voltage
when the malfunction occurs is a good indication that
there is a fault in the circuit being monitored.
Use a Tech 2 to help detect intermittent conditions. The
scan tool has several features that can be used to locate
module (PCM) and
Perform the
The fault must be
This requires
an intermittent condition. Use the following feature to find
intermittent faults:
f Using a Tech 2's "Freeze Frame" buffer or "Failure
Records" buffer can aid in locating an intermittent
condition. Review and record the information in the
freeze frame or failure record associated with the
intermittent DTC being diagnosed. The vehicle can
be driven within the conditions that were present
when the DTC originally set.
To check for loss of diagnostic code memory, disconnect
the MAP sensor and idle the engine until the MIL (Service
Engine Soon lamp) comes on. DTC P0107 should be
stored and kept in memory when the ignition is turned
"OFF." If not, the PCM is faulty. When this test is
completed, make sure that you clear the DTC P0107 from
memory.
An intermittent MIL (Check Engine lamp) with no stored
DTC may be caused by the following:
f Ignition coil shorted to ground and arcing at ignition
wires or plugs.
f MIL (Check Engine lamp) wire to PCM shorted to
ground.
f Poor PCM grounds.
diagrams.
Check for improper installation of electrical options such
as lights, cellular phones, etc. Check all wires from the
PCM to the ignition coils for poor connections.
Check for an open diode across the A/C compressor
clutch and check for other open diodes (refer to wiring
diagrams in Electrical Diagnosis ).
If problem has not been found, refer to PCM Connector
Symptom tables.
f Check the "Broadcast Code" of the PCM, and
compare it with the latest Isuzu service bulletins
and/or Isuzu EEPROM reprogramming equipment to
determine if an update to the PCM's reprogrammable
memory has been released. To check the "Broadcast
Code," connect the Tech 2, then look for "ID info," then
select "Broadcast Code." This should display a 4
character code, such as "XBYA" (example only). This
identifies the contents of the reprogrammable
software and calibration contained in the PCM. If the
Broadcast code is not the most current available, it is
advisable to reprogram the PCM's EEPROM
memory, which may either help identify a hard-to-find
problem or may fix the problem.
Refer to the PCM wiring