Checks
| Action
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DEFINITION: The
problem may or may not turn ON the malfunction indicator lamp (MIL) or store
a diagnostic trouble code (DTC). If a DTC was stored and the DTC diagnostic
table indicates the fault is not present an Intermittent Condition is
indicated.
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Preliminary Checks
| Refer to Important Preliminary Checks in
Symptoms - Engine Controls
.
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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:
| • | Connectors that are poorly mated |
| • | Terminals that are not fully seated in the connector (backed out) |
| • | Terminals that are not properly formed or damaged (may be due
to improper diagnostic probing procedures) |
| • | Poor terminal retention (male to female connection)--Checking
for proper terminal retention requires the use of the J-38125
terminal repair kit. |
| • | Wires that are broken inside the insulation |
| • | 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
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 two 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 multimeter 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 monitored on the scan tool under the Not Ran Since Code Cleared
selection in the DTC Information menu. If the DTC appears in the Not Ran
Since Code Cleared list, the DTC diagnostic has not yet run. When the
DTC does not appear in the Not Ran Since Code Cleared list, the DTC diagnostic
has run. If the MIL is NOT ILLUMINATED and there is no PENDING DTC Status
in DTC Information, the DTC diagnostic has passed. DTCs MUST BE CLEARED
in order to view the CURRENT STATUS of the Not Ran Since Code Cleared
list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates
that the test has run, not whether the test passed or failed. The DTC
Information screen must be checked for CURRENT or PENDING status, in
order to determine the outcome of the diagnostic test involved. |
|
Scan Tool
| The scan tool features that can be used to locate intermittent conditions
include the following:
| • | 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 data values taken from a similarly
equipped known good vehicle. |
| • | Freeze Frame/Failure Records data feature--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, engine parameters are also stored. This
stored information can be reviewed and compared to the typical
Scan Tool Data List
values or data values taken
from a similarly equipped known good vehicle. |
| | Freeze Frame/Failure Records data will be erased when DTC Information
is cleared either by scan tool clearing or by disconnection of the control
modules (AF ECU, VCM/PCM or 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. |
| • | Ignition control (IC) wires routed near the generator or near
secondary ignition system wires and components |
| • | Ignition system secondary voltage that is shorted to ground |
| • | Poor ignition control circuit or ignition module grounds |
| • | The MIL control circuit intermittently shorted to ground |
| • | 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 powertrain
control module (PCM) and remain in memory when the ignition is turned OFF.
Failure to store a DTC or failure of the DTC to remain in memory may
indicate a faulty PCM.
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Additional Checks
|
| • | Check for open diodes (A/C clutch, charging system, etc.) that
may cause electrical interference. |
| • | If the intermittent fault is suspected to involve a particular
sensor or component, observe the sensor or component display on a scan tool
while moving connectors and wiring harnesses related to the sensor or component.
A change in the scan tool display can indicate the location of the fault. |
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