Checks
| Action
|
DEFINITION: The
problem may or may not turn ON the MIL or store a DTC. There is a customer
concern, but the symptom can not currently be duplicated, or the DTC diagnostic
table indicates the fault not present at this time.
|
Preliminary Checks
|
| • | The fault must be present in order to be diagnosed correctly with
a DTC table. If the fault that set the DTC is intermittent, then the use of
DTC tables may result in replacement of good parts. |
|
Electrical
Connections or Wiring
| Electrical connections and wiring cause most intermittent conditions.
Determine which circuit is suspected of having an intermittent condition.
This may be indicated by DTCs with a fault not present.
Check the suspect circuit for the following conditions:
| • | Any connectors that are poorly mated |
| • | Any terminals that are not fully seated in the connector |
| • | Any terminals that are not properly formed or damaged |
| • | A poor male to female connection--Checking for proper terminal
retention requires the use of the J-38125
Terminal Repair Kit. |
| • | Any wires that are broken inside the insulation |
| • | A pierced or damaged insulation that allows water or moisture
to enter the wiring--The conductor can corrode inside the insulation
with little visible evidence. Look for swollen and stiff sections of
wire in the suspect circuit. |
Refer to
Wiring Repairs
and to
Connector Repairs
in Wiring Systems for the
proper procedures to use when making a circuit repair.
|
Road Test
| The following tests should
be performed with 2 people in order to ensure the safe operation of the
vehicle.
| • | Drive the vehicle while monitoring the suspect circuit with a
scan tool or a DMM connected to the circuit. Look for an abnormal
reading or voltage when the malfunction occurs. An abnormal reading on
the scan tool or an abnormal voltage on the DMM display is an indication
that there may be a malfunction in the circuit that was being monitored. |
| • | If the intermittent fault sets a DTC, the diagnostic that sets
the DTC can be enhanced using Check Mode. Operating the vehicle while in Check
Mode can enable certain DTC diagnostics to run faster. Check Mode also turns
some B type DTCs to A type DTCs. Refer to
Service Bay Test
. |
| • | Certain DTCs must run before I/M system status can be determined.
Any DTC that affects the status of an I/M system can be monitored indirectly
on the scan tool under the I/M System Information selection. In order
to determine which DTCs are associated with a particular I/M system test,
refer to
Inspection/Maintenance (I/M) System DTC Table
. If an intermittent DTC is associated with a particular
I/M system, monitoring the I/M system test can indicate whether the diagnostic
for that DTC has run. When the I/M system test displays a YES status,
indicating that the system diagnostic is complete, check for the
applicable DTC in the Last Test Failed screen of the scan tool. If
the DTC is not displayed, the diagnostic for that DTC has run and passed,
indicating that no malfunction was present this time. All DTCs
MUST BE CLEARED in order to view the Current Status of the I/M
system tests. Do not forget that the I/M System Information tests
only indicate that the test has run, not if the test passed
or failed. The Last Test Failed screen must be checked for
related DTCs in order to determine the outcome of the diagnostic
test involved. |
|
Scan
Tool
| The scan
tool features that can be used to locate an intermittent conditions include
the following:
| • | The scan tool Snapshot feature--The scan tool Snapshot feature
can be triggered to capture and store engine parameters when a malfunction
occurs. This stored information can be reviewed and compared to
the Typical Scan Tool Data Values or to data values taken from a
similarly equipped known-good vehicle. |
| • | The Freeze Frame/Failure Records data feature--The Freeze
Frame/Failure Records are stored when certain DTCs set. They typically include
information to aid in reproducing the driving conditions that were
present when a DTC is stored. In addition, the engine parameters are
also stored. This stored information can be reviewed and compared
to the typical
Scan Tool Data List
values or to data values taken from a similarly equipped known-good
vehicle. |
| | The Freeze Frame/Failure Records data will be erased when DTC Information
is cleared either with the scan tool or by disconnection of the control
modules ECU, vehicle control module/powertrain control module (VCM/PCM),
or engine control module (ECM) power supply. |
|
Intermittent
malfunction indicator lamp (MIL)
| The following conditions may cause intermittent MIL operation
with no DTCs stored:
| • | A defective relay, control module driven solenoid, or a switch
that causes electrical system interference--Usually the symptom will
occur when the faulty component is operating. |
| • | Any ignition control (IC) wires routed near the generator or near
the secondary ignition system wires and components |
| • | An ignition system secondary voltage that is arcing and shorting
to ground |
| • | Any poor ignition control circuit or ignition module grounds |
| • | A MIL control circuit that is intermittently shorting to ground |
| • | Any faulty diodes in the generator or charging system circuits |
| • | The improper installation of add-on electrical devices--These
can include the following: |
|
Loss
of DTC Memory
| In order to check for proper DTC Memory function, perform the following procedure:
- Observe the Conditions For Running The DTC for the throttle position
(TP) sensor circuit low voltage DTC.
- Disconnect the TP sensor connector.
- Operate the vehicle within the Conditions for Running the DTC.
- The MIL should illuminate upon completion of all the Conditions
for Running the DTC. Two key cycles or drive trips may be required.
- A TP sensor circuit low voltage DTC should be stored in the PCM
and remain in memory when the ignition is turned OFF.
A failure to store a DTC or failure of the DTC to remain in memory may
indicate a faulty PCM.
|
Additional Checks
|
| • | Check for open diodes (A/C clutch, charging system, etc.) that
may cause electrical interference. |
| • | The improper installation of add-on electrical devices--These
can include the following: |
| • | If the intermittent fault is believed to involve a particular
sensor or component, observe the sensor or component display on a scan tool
while moving the connectors and the wiring harnesses related to the
sensor or the component. A change in the scan tool display can indicate
the location of the fault. |
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